Chapter 1 morphology,structure
and function of prokaryotes
原核生物的形态，结构和功能
Prokaryotes and eukaryotes
major differences
section A
Within the microbial world can be found two
different categories of cell type/ prokaryote
and eukaryote,
DNA free in the cytoplasm
Only one chromosome
DNA associated with
histone-like proteins
May contain
extrachromosomal
elements called Plasmids
Introns not found in mRNA
Cell division by binary
fission - asexual replication
only
Transfer of genetic
information occurs by
conjugation,transduction
and transformation
DNA is contained with a membra-
ne bound nucleus,A nucleolus is
also present
>1 chromosome,Two copies of
each chromosome may be present
(diploid)
DNA complexed with histone
proteins
Plasmids only found in yeast
Introns found in all genes
Cells divide by mitosis
Exchange of genetic information
occurs during sexual reproduction,
Meiosis leads to the production
of haploid cells (gametes) which
can fuse
原核生物和真核生物遗传的和细胞组装上的主要差别
DNA在细胞质中游离
只有一个染色体
DNA与类组蛋白连系
含有染色体外的遗传物质，称为质粒
在 mRNA中没有发现内含子
细胞分裂以二等分裂方式，只有无性繁殖
遗传信息传递可通过接合、转导、转化发生
DNA在膜包围的核中，只有一个核仁
多于一个染色体，每个染色体是双拷贝 (双倍体 )
DNA与组蛋白连系
只在酵母中发现质粒
所有基因中都发现内含子
细胞分裂为有丝分裂
遗传信息交换发生在有性繁殖过程，减数分裂导致产生
单倍体细胞 (配子 )，它们能融合
.原核生物,真核生物遗传物质的组装和复制
1,Cytoplasmic membrane contains hopanoids lipopoly-
saccharides,and teichoic acids found
2,Energy metabolism associated with the cytoplasmic
membrane
3,Photosynthesis associated with membrane systems and
vesicles in cytoplasm
4,Flagella consist of one protein,flagellin
5,Ribosomes - 70S
6,Peptidoglycan cell walls (eubacteria only:different polymers
in archaebacteria)
Cellular organization of
prokaryotes
1,Cytoplasmic membrane contains sterols
2,Mitochondria present in most cases
3,Chloroplasts present in algal and plant cells
4,Internal membranes,endoplasmic reticulum and Golgi
apparatus present associated with protein synthesis and
targetting
5,Membrane vesicles such as lysosomes and peroxisomes
present
Cellular organizaton
of eukaryotes
6,Cytoskeleton of microtubules present
7,Flagella have a complex structure with 9+2
microtubular arrangement
8,Ribosomes – 80s(mitochondrial and
chloroplast ribosomes are 70S)
9,Polysaccharide cell walls,where present,are
generally either cellulose or chitin
质膜含有 hopanoids、脂多糖和磷壁酸
能量代谢与细胞质膜连系
光合作用与细胞质中膜系统和泡囊连系
由一根蛋白鞭毛丝构成鞭毛
核糖体 ——70S
肽聚糖的细胞壁 (只有真细菌有，古细菌中是不同的
多聚体 )
质膜含有固醇
多数情况在线粒体中发生
藻类和植物细胞中存在叶绿体
蛋白质合成和定向运输与内膜、
粗面内质网及高尔基体有关
有膜囊泡如溶酶体和过氧化物酶体有微管骨架
核糖体 ---80S，细胞壁多糖一般是纤维素或者是几丁质细胞组装
Rough ER
Golgi
mitochondria
Choloroplast
Cell wall of eukaryote
细胞核示意图
Nuclear spore
chromatin
cytoskeleton
一切真核细胞都有一套由蛋白质丝组成的细胞内部骨架。它不仅有助于细胞内部活动的条理化，并且是细胞运动及形态变化的基础。
Cytoskeleton of cultured cell
肌动蛋白丝微管中间丝当一个细胞分裂时，其核膜被解离，且其 DNA浓集成可见的染色体对，它们被微管拉开至两个分裂的自细胞中，微管从分裂细胞相对的两极会聚点辐射出去。
一个正在分裂的细胞中的微管
Lysosome——a kind of organelle in animal cell
A comparison of the main features of these
two categories of cell is shown in the table
discussed,but other differences do occur,
Although the basic mechanisms of DNA
replication,RNA synthesis and protein
synthesis are the same in both prokaryotes and
eukaryotes,there are differences in the
components and enzymes involved,These are
discussed in the appropriate topics.
Major groups of prokaryotes
bacteria
actinomyces Cyanobacteria
Spirochetes
others Rickettsia
Chlamydia
Mycoplasmas
杆菌原核生物常见种类和常见形态（ 1）
球菌原和生物常见种类和常见形态（ 2）
蓝细菌（螺旋藻）
蓝细菌（鱼腥草）
原和生物常见种类和常见形态（ 3）
古细菌（产甲烷细菌） 细菌（耶尔森鼠疫杆菌）
Bacteria are small (< 1um-50um width/diameter),
single-celled,micro organisms that belong to a group
called prokaryotes so classified because their DNA is
not enclosed within a nuclear membrane,
definition
Section B bacterium
Because they lack,a distinct nuclear
membrane,the organelles associated with
energy generation,such as mitochondria
and chloroplasts,and complex internal
membranes,such as endoplasmic
reticulum and Golgi apparatus,which are
found in eukaryotes.
Why bacteria are prokaryotes?
They are a highly successful and diverse
group of organisms that can obtain energy and
carbon from a wide range of sources and
therefore can colonize（定居） every niche on
our planet from deep ocean trenches to
volcanic craters,
Bacteria are ubiquitous
In the 1970s,using DNA sequencing information,it
was found that the group we know as the bacteria
could be split into two,the eubacteria (Gr,eu,true and
bakterion,a small rod) and the archaebacteria (Gr,
Archaios,ancient) and it appears that these two groups
evolved away from each other very early in the history
of living things at about the same time that the first
group of eukaryotic cells evolved,（ 是一个在进化途径上很早就与真细菌和真核生物相互独立的生物类群 ）
1,eubacteria and archaebacteria
On the basis of 16S RNA sequences,it is now clear that there
are (at least) three domains of organisms,the two prokaryotic
groups,archaebacteria and eubac-teria and the eukarya (Fig),
Within the eubacteria there are at least 11 groups,referred to
sometimes as phyla,which can be represented on a phylogenetic
tree,What can be seen is the wide diversity within the bacterial
world and that may be familiar to us such as E,Coli,bacillus
species are located within just a few of these phyla,It should be
noted that the number of phyla will increase as more bacteria
from diverse habitats are sequenced.
An overview of the phytogeny of the living world,showing the three major
domains of organisms,the Eubacteria,the Archaebacteria and the Eukarya,
a Members of the eubacteria include some of the
more familiar bacteria such as Escherichia coli and
Staphilococcus aureus and are the prokaryotes that
are best studied and understood,
The archaebacteria are a very diverse group of organisms,
which differ from the eubacteria in a number of features havi-ng,
in particular,very different cell walls and membranes,This g
roup includes bacteria that are capable of existing in extreme
environments,such as hot springs (examples,Sulfolobus and
Pyrococcus) and high salinity (Halobacterium),and the meth
anogens such as Methobacterium,which produce methane as a
result of metabolism.主要包括一些独特生态类型的原核生物，如产甲烷菌及大多数的嗜极菌（ extremophile），包括极端嗜盐菌、极端嗜热菌和热原体属（ Thermoplasma）
古细菌（产甲烷细菌）
A list of the types of characters used to distinguish
between bacteria is given below,This is not an
exhaustive list and equally not all characters are used in
either the classification or identification of every
bacterial species,In many cases of well known
microorganisms,a small set of tests may be all that is
required to identify a microbe positively,especially if
the site from which it has been isolated and the disease
it caused are known,
Characters used in bacterial identification
A comma-shaped,Gram-negative rod
isolated from a patient excreting copious
amounts of straw-colored,liquid stools may be
enough to identify it putatively as Vibrio cholera,
the causative agent for cholera,However,it may
be necessary to do a wide range of tests to
determine the name of an isolate if it is an
undescribed microbe.
The shape,texture and color of bacterial
colonies can be distinctive,For example,
Staphylococcus aureus is so named as
colonies are of a yellow color; 'aureus' comes
from the Latin for golden.
1.Colony morphology.
Whether bacteria are Gram-positive or Gram-negative is one
of the most important clinical diagnostic tests,Gram staining
and microscopic examination of bacteria give information as to
the shape,size and arrangement of the bacterial cells and in
some cases this is enough to identify certain genera such as
Streptococci which are Gram-positive cocci that grow in chains,
Stains may also be used to show other morphological features,
which may be used for classification,such as the presence of:
spores (malachite green stain);
unusual cell walls (Ziehl Neelsen acid-fast stain);
capsules (Indian ink stain);
intracellular lipids (Sudan black);
flagella (flagellar stain);
metachromatic granules (Albert-Leybourne stain).
2.Cell shape,structures and reaction to stains
The temperature,pH and 0;
requirements of an isolate are
useful tests for the identification of
bacteria.
3.Growth characteristics.
There is a wide range of tests available that
measure various aspects of bacterial metabolism:
what carbon and nitrogen sources the bacteria
can use;
the end products of their metabolic processes,
such as acetoin,tested for in the Vogues-Proskaeur
test;
what enzymes the bacteria produce,such as
decarboxylases,proteases and DNases;
the presence of other molecules such as toxins,
long- chain fatty acids or antibiotics.
Biochemical tests
Antibodies to cellular components such as
the 0-side chains of lipopolysaccharide (LPS)
(Topic D3) or capsules are frequently used to
distinguish between strains of one species.
Immunological tests
Comparisons of DNA content and sequence between strains
are the most definitive methods for separating organisms into
different groups and for measuring the evolutionary
relatedness between them (phylogenetic analysis),Traditionally,
DNA was analyzed by measuring the G-C content or the amount
of DNA homology between strains,More recently,the
comparison of the actual DNA sequences of conserved cellular
molecules such as 16S ribo-somal RNA or proteins such as
cytochrome C,ATPase and elongation factor has been used,
This information has been analyzed by a tech nique called
cladistics to trace true phylogenetic lineages that have not been
obscured by patterns of convergent evolution,
DNA tests
The main impetus for bacterial classification has been
the need to be able to identify bacterial disease-causing
organisms and therefore these microbes are particularly
well classified,However,it should be remembered that
many other species have not been well characterized
and many have not been isolated or described at all,
The authority on bacterial classification is Bergey's
Manual of Systematic Bacteriology,which contains as
near as possible complete listings of all prokaryotic
species and their distinguishing characteristics.
Classification of bacteria
ranked are,sequentially,family,order,class,division
and kingdom,though the final three are not particularly
useful in bacteriology,Similarly,species may be divided
into subspecies and a culture of a particular organism
is usually referred to as a strain,Strain is also used to
describe a sub-group of a species that share some
feature such as one type of 0-antigen or mutation,
There are also informal names,not italicized,which are
sometimes useful for describing groups of organisms
such as the green-sulfur bacteria or the spiro-chetes.
Classification of bacteria
In spite of this simplicity in structure there is
a large amount of variation in the appearance
of the cells when observed under the microscope,
Two shapes of cell predominate,the coccus
(spherical) and the bacillus,or rod,but there
are also a wide range of other shapes
(morphologies)
2.Bacterial shapes
2.1 Individual
shapes
Organization of cells Examples
Cocci In chains Streptococcus
spherical bacteria In grape-like clusters Staphylococcus
In pairs (diplococci) Neisseria
In cubes of cells (packets) Sarcina
single Micrococcus ureae
（ 1） coccus
球菌 (coccus)
脑膜炎奈瑟菌双球菌 (diplococcus)
肺炎链球菌链球菌 (streptococcus)
球菌 (coccus)
球菌 (coccus)
葡萄球菌 (streptococcus)
球菌 (coccus)
四联球菌 (tetrad)
球菌 (coccus)
八叠球菌 (sarcina)
杆菌 (bacillus)
不同杆菌的大小、长短、粗细很不一致。
炭疽芽胞杆菌 3-10 μ m
大 中大肠埃希菌 2-3 μ m
小布鲁菌 0.6-1.5 μ m
杆菌的形态多样杆菌 (bacillus)
两端齐平炭疽芽胞杆菌两端尖细白喉棒状杆菌杆菌 (bacillus)
杆菌的形态多样分枝杆菌 双歧杆菌螺形菌 (spiral bacterium)
弧菌 螺菌 螺杆菌化脓性链球菌
Streptococcus
pyogenes - coccoid
prokaryote; causes
pharyngitis,sinusitis,
otitis media (middle ear
infection),food
poisoning,puerperal
fever (childbed fever),
skin and wound
infections (scarlet fever,
erysipelas,impetigo),
Group A strep,SEM
x56,000
粪链球菌 Streptococcus
faecalis - coccoid prokaryote;
a pathogen causing skin and
wound infections
链球菌
Rods/bacilli - rods may be very short (cocci-bacilli) or long
Singly Pseudomonasa
In filaments of attached cells Bacillus sp.
Most bacteria used in industry are bacillus
Bacillus subtilis to produce,amylase and protease
Coroynebacterium pekinense used for glutamic acid
Lactobacillus bulgaricus used in milk industry
（ 2） bacillus
结核杆菌 Mycobacterium
tuberculosis,Rod-shaped
Bacterium (SEM x40,000)
白喉杆菌 Corynebacterium
diphtheriae,Rod,clubed-
shaped Bacterium (causes
diphtheria)
Plastic kitchen cutting board surface -
rod bacteria in a smooth matrix;
filamentous bacteria ( 丝状菌 ) -smooth
oval cells; fungal hyphae ( 真菌菌丝 )
with textured spores ( 结构孢子 ) (x
2,270)
Rod-Shaped Bacterium,E,coli (SEM
x22,245) E,coli (0157:H7) - a rod
prokaryote,Hemorrhagic type
痢疾杆菌 Shigella sonnei - rod
prokaryote; causes shigellosis
(bacterial dysentery) (x 22,400)
伤寒杆菌 Salmonella - rod prokaryote; note the flagella,Causes
salmonellosis (food poisoning),(x
20,800)
大肠杆菌棒状杆菌肠杆菌
Comma shaped - called a vibrio Vibrio
Spirillum - long,curved,rigid rods Rhodospirillum
A Tightly coiled flexible bacteria –spirochaetes Treponema 柔软易曲的紧螺旋 如：密螺旋体属 Rhodospirillum
疏螺旋体属 Borrelia
B Appendaged - cells have stalk or tube-like extensions
如红微菌属 Rhodomicrobium
C Pleomorphic - bacteria vary in shape
如棒杆菌属 Corynebacteria
D Branching mycelium-like filaments Streptomyces
（ 3） spirillum and vibrio
（ 4） others
霍乱弧菌 Vibrio cholerae - vibrio-
shaped prokaryote that causes
cholera (x 15,575)
Bdellovibrio bacterovorus
它有一条端生鞭毛，这种细菌攻击并杀死比它更大的细菌且以其为食物。
螺旋杆菌 Spirochete bacteria
红弧菌螺菌螺旋菌
Measure Unit,um
Description：
Bacillus ——width× length （ 0.20~1.25） × （ 0.300~8.00)
Spirillum——width× length （ 0.3~1.0） × （ 1.0~5.0）
Coccus—— diameter 0.20~1.25
3,size of bacteria
Basic structure
Cell wall
Cytoplasmic
membrane
Mesosome
Protoplast
Nucleus
Ribosome
Inclusion body
Special structure
Flagella
Capsule
spore
4,structure
细菌的结构基本结构 细胞壁、细胞膜、细胞质、核质特殊结构 荚膜、鞭毛、菌毛、芽胞一,基本结构
（一）细胞壁 (cell wall)
革兰阳性菌革兰阴性菌革兰染色两类细菌细胞壁的共同组分为肽聚糖，但各有其特殊组分。
革兰染色法：
涂片 风干 固定结晶紫 碘液 95%乙醇 复红1min 1min 脱色
1,肽聚糖 (peptidoglycan)
革兰阳性菌肽聚糖 — 聚糖骨架、四肽侧链、五肽交联桥青霉素作用点溶菌酶作用点
N-乙酰葡糖胺
N-乙酰胞壁酸革兰阴性菌肽聚糖 — 聚糖骨架、四肽侧链
1,肽聚糖 (peptidoglycan)
2,革兰阳性菌细胞壁特殊组分壁磷壁酸膜磷壁酸
3,革兰阴性菌细胞壁特殊组分
3,革兰阴性菌细胞壁特殊组分脂多糖 (lipopolysaccharid,LPS)
革兰阳性菌与阴性菌细胞壁结构比较细胞壁 革兰阳性菌 革兰阴性菌强度 较坚韧 较疏松厚度 20-80nm 10-15nm
肽聚糖层数 可多达 50层 1-2层肽聚糖含量 占细胞壁干重 50%-80% 占细胞壁干重 5%-20%
磷壁酸 + —
外膜 — +
脂蛋白 — +
脂多糖 — +
维持菌体固有的形态
保护细菌抵抗低渗环境
参与菌体内外的物质交换
菌体表面带有多种抗原分子，可诱发机体的免疫应答。
4,细胞壁的功能
Fig,1,Diagram of a prokaryote cell (Gram-negative).
4,structure
pilus
细菌细胞的透射电子显微镜照片及模式图
Their internal cell structure is simple,most of
the cellular complexity associated with the cell
surface structures,Bacteria lack mitochondria
and chloroplasts（叶绿体）,the organelles
associated with energy production in eukaryote
cells and internal membrane structures such as
the endoplasmic reticulum and Golgi apparatus,
although some photo-synthetic bacteria do have
internal membranes.
The cytoplasm of all bacteria is enclosed within
a plasma (cytoplasmic) membrane external to which,
in most cases of eubacteria,is a rigid cell wall made
up of sugars and amino acids called peptidoglycan,
The role of the cell wall is to protect the cell from
lysis resulting from osmotic pressure and it also
gives shape to the cell.
4.1 Cell wall
Some bacteria,the mycoplasma,do not have cell walls
and therefore are unable to survive outside an animal
host which provides it with the right osmotic
environment,Gram-negative bacteria have an additional
outer membrane（外膜又称外壁层 ） containing LPS,
External to this may be other layers of poly-saccharide
or protein making up a capsule or slime layer,Layers
external to the cell wall may be referred to as the cell
envelope细胞外膜,The structure of the eubacterial cell
envelope is discussed in more details.
summerize
1.Position,cytoplasm——cytoplasmic membrane—
—cell wall——（ out membrane） ——cell envelope
（ capsule or slime）
2.Major Function,The role of the cell wall is to protect
the cell from lysis resulting from osmotic pressure and
it also gives shape to the cell.（固定细胞外形和提高机械强度，使其免受渗透压等外力的损伤 ）
3.Composition：
G+ peptidoglycan,teichoic acid（磷壁酸）
G- peptidoglycan,lipopolysaccharide（ LPS）,outer
membrane proteins
Outside the plasma membrane is the cell wall made of
sugars and amino acids called the peptidoglycan (sometimes
called the murein layer),The role of the cell wall is to
provide rigidity and strength,preventing the cell from
osmotic lysis when placed in dilute environments,The
structure of peptidoglycan from E,coli is shown in the
following slide,It consists of long polymers of two sugar
derivitives,NAG and NAM with side chains of four
alternating D- and L-amino acids attached to the NAM,
Rigidity is achieved by crosslinks between the amino acid
chains; normally from the third amino add in one chain to the
fourth amino acid in another chain,The nature of the amino
acid side chains,and the links that join them,vary between
bacterial species; however,the third amino acid is always a
diamino acid (has two amino groups,so can form links) and
the fourth amino acid is normally D-alanine (D-Ala),
Fig,3,Structure of the E,coli peptidoglycan showing
crosslinks between two strands,NAG,N-acetyl-
glucosamine,NAM,N-acetylmuramic add,D-Ala,D-
alanine,DAP,rrieso-diaminopimelic acid; D-Glu,D-
glutamic
In E,coli and most other Gram-negative bacteria
there is a direct link between the diamino acid meso-
diaminopimelic acid（内消旋二氨基庚二酸 DAP） and
D-Ala,In Gram-positive bacteria the linkage often
contains a bridge of amino acids,for example,in
Staphylococcus aureus there is a five amino acid
(pentapeptide) bridge of glycines between D-Ala and L-
lysine,Multiple crosslinks within and between chains
makes peptidoglycan a very strong and rigid structure,
There are several unique features of
peptidoglycan including:
the presence of NAM; this sugar is not found in
eukaryotic cells;
the presence of D-amino acids; L-amino acids are
normally found in proteins.
These features make the peptidoglycan a target for
antimicrobial agents that destroy prokaryotic cells specifically,
but do not harm eukaryotic cells; an example of this is the
antibiotic penicillin,Lysozyme,a natural antibacterial agent
found in tears and natural secretions,breaks down the
linkage between NAM and NAG（散架）,
Removal of the cell wall under conditions where the
osmolarity of the medium is the same as the inside of
the cell (isotonic solution) results in the formation of
round protoplasts原生质体 (Gram-positives) or
spheroplasts 球质体 (Gram-negatives) which survive
as long as the isotonicity is maintained,These
structures lyse,however,if placed in a dilute medium,
illustrating the importance of peptidoglycan to the
cells‘ survival.
Gram-positive cell walls also contain large amounts of
another polymer,called teichoic acid,made up of glycerol
or ribitol joined by phosphate groups,D-Ala,glucose or
sugars may be attached to the glycerol or ribitol and the
poly mers are attached either directly to the NAM in the
peptidoglycan or to lipids in the membrane (in this case
they are called lipoteichoic acids),The function of these
molecules is unclear but they may have a role in
maintaining the struc ture of the cell wall and in the
control of autolysis.
Nocardia诺卡氏菌属,contain waxy esters of
Cell walls of a number of genera including
Mycobacterium(分支杆菌属 ),
Corynebacterium (棒状杆菌 )
and mycolic acids(分枝菌酸 ),which are
complex fatty acids.
One of the distinctive features of archaebacteria is the
nature of the lipids in the plasma membrane which,unlike
the ester-linked lipids of eubacteria and eukaryotes are
ether-linked to glycerol,They are also long chained and
branched,Archaebacterial cell walls and envelopes show
great diversity and complexity in structure,They do not
contain peptidoglycan although some do have a similar
compound called pseudomurein(假肽聚糖 ) which contains N-
acetyl-alosaminuronic acid in place of muramic acid,
Another common type of cell wall is the S-layer,a two-
dimensional,paracrystalline,array of| protein or
glycoprotein on the cell surface,Others have thick
polysaccharide walls outside their plasma membrane.
Archaebacterial cell wall and surface
The plasma membrane is a semi-permeable lipid
bilayer which acts as a barrier between the cytoplasm
and the surrounding environment,The membrane is
made of phospholipids,such as phosphatidyl choline
（磷脂酰胆碱）,which consist of a polar headgroup
attached via glycerol to two long chains of non-polar
fatty acids,Such molecules which consist of both polar
and non-polar groups are called amphipathic（两性分子）,
4.2 Cell membrane
The polar headgroups are hydrophilic
(Gr,hydro,water;philic,loving) and the
fatty acids are hydrophobic (Gr,
phobis,hating) which means that in an
aqueous environment these molecules
line up to ensure that the polar
headgroups are associated with the
water molecules and the hydrophobic
chains are tucked away in the interior
of the bilayer away from the water,
Hence,a bilayer can be formed,called
a membrane,about 5-10 nm thick,
The interior of the membrane is highly hydrophobic,
therefore acting as a barrier to anything that is bulky,such as
glucose,or highly polar,such as ions,Small molecules like
water can diffuse through and hydrophobic compounds such
as benzene(苯 ) can also move through by dissolving in the
hydrophobic interior,Bacterial membranes do not contain
sterols(固醇 ) such as cholesterol which provide stiffness in
higher organisms(高等生物中维持细胞膜稳定的胆固醇 ),
However,recently it has been shown that sterol-like
molecules called hopanoidsare found in bacterial membranes
Embedded in the lipid bilayer are proteins of various
functions including transport proteins,proteins involved in
energy metabolism and receptor proteins that can detect and
respond to chemical stimuli,Integral proteins are those that are
fully associated with the membrane and may penetrate all the
way through,These proteins therefore contain hydrophobic
amino acids in the regions which are buried in the lipid,
Peripheral proteins are ones that are only loosely associated by
charge interactions with the positively charged polar
headgroups of the phos-pholipids or on integral proteins and
can be removed from purified membranes by washing with salt
solutions,
The lipids and proteins are fully mobile and move in relation to each
other,This widely accepted model of membrane struc ture is called
the fluid mosaic model,
Hydrophillic
region
Diagram of the structure of the plasma membrane.
Hydrophobic
region
Hydrophilic
region
Polar
headgroup
Fatty acid
chains
phospholipid
Peripheral protein
Integral protein
The outer membrane of Gram-negative bacteria is made up of
phospholipids(磷脂 ) but it also contains some unique features,
Pores formed by proteins called porins(孔蛋白 ) such as OmpF
and OmpC that allow the passive diffusion of small molecules into
the periplasmic space(周质空间 ).
An abundant small lipoprotein called Braun‘s lipoprotein(布朗脂蛋白 ) that is covalently bound to the peptidoglycan and is
embedded in the outer membrane by its hydrophobic lipid,
therefore holding the peptidoglycan and outer membrane close
together.
LPS molecules are found in the outer leaflet of the outer
membrane projecting into the surrounding medium.(LPS分子位于外膜的外叶伸向周围的培养基中 )
4.3 outer membrane
Porin(trimer)
Braun’s
lipoprotein
O-specific sidechain
LPS
Lipid A
peptidoglycan
Diagram showing the structure of the outer membrane
of a G- bacterium
1.The outer membrane of Gram-negative bacteria acts as an
additional barrier protecting the peptidoglycan from toxic
compounds such as lysozyme which act on the cell wall,
2,It creates an aqueous space between the two membranes
called the periplasmic space which is thought to have a gel-
like structure with a loose network of peptidoglycan running
through it,Estimates as to the width of the peptidoglycan
vary from 1-71 nm but it has proved to be difficult to obtain a
real definitive value,
Role of the outer
membrane
transport of nutrients into the cell;(营养物的运输 )
enzymes that are involved in nutrient
acquisition such as proteases;
enzymes that defend the cell against toxic
chemicals such as β-lactamases that destroy
penicillin.(细胞防御有毒化合物 )
The periplasmic space contains a range of
proteins associated with:
In Gram-positive cells these enzymes (called
exoenzymes) are normally secreted into the
surrounding medium,The presence of the outer
membrane in Gram-negative bacteria allows the
cell to keep the enzymes close to itself rather,than
losing them into the medium.
Lipid A which is embedded in the membrane.
A core polysaccharide which contains a number of
unusual sugars including 2-keto-3-deoxyoctonate (KDO).
A side chain of repeating sugars called the 0-antigen or
0-side chain,The composition of the 0-side chain varies
between strains and antibodies to the 0-antigen are often
used for typing bacteria in the laboratory.
LPS consists of three parts:
they cause a net negative charge on the surface of the cell;
they may hinder the access of toxic molecules to the surface of
the cell there fore play a protective role ;
the long side chains are capable of variation in structure therefore
may play a role in allowing Gram-negative bacteria to evade the
immune response,
Most importantly,the lipid A portion of the LPS molecule is highly
toxic to mammals,Called endotoxin,its presence in the blood
stream,even at very low concentrations,leads to toxic shock and
death,
LPS is responsible for a number of features
of the Gram-negative bacterium:
The cytoplasm of bacteria is aqueous,
containing a cocktail of molecules,
ribonucleic acid (RNA) and proteins
necessary for the cell functions,
Basic structure
4.4 cytoplasm
A The main structures,common to all bacteria,found in the
cytoplasm are the ribosomes,
B The ribosomes which consist of a small and a large subunit,
made up of a complex of proteins and RNAs,
C are the sites of protein synthesis in the cell,
4.5 Ribosomes
Basic structure
The ribosomes in prokaryotic cells,although similar
in shape and function to those of eukaryotic cells,are
different in the nature of the proteins and RNAs that make
up their structure This has proved to be very useful to the
human population as antibiotics that act by inhibiting
protein synthesis in bacteria are not effective against
eukaryotic protein synthesis,thus allowing selective
toxicity,
ribosome
Archaebacterial ribosomes are the same size as those of the
eubacteria but,in some features,they are similar to eukaryotic
ribosomes in that they are resistant to the antibiotics,streptomycin
and chloramphenicol,and sensitive to the action of diphtheria toxin
Basic structure
Bacterial DNA is located within the cytoplasm,It
consists of a single chromosome which varies in size
between different species of bacteria (the E,coli
chromosome is 4 x 106 base pairs long),The DNA is
circular,tightly supercoiled（致密超螺旋） and
associated with proteins which are similar to the histone
proteins found in eukaryotic cells Although the
chromosome is not contained within a nuclear membrane,
it is often seen as a discrete （分离的） area within the
cell in electron micrographs which may be referred to as
the nucleoid.
4.6 Genetic material
nucleoid
Basic structure
Some bacteria also contain small molecules of extra-
chromosomal DNA called plasmids,These often carry
genes which are not essential to the normal life of the cell
but confer an advantage to the cell in certain situations
such as antibiotic-resistant plasmids,The chromosome in
archaebacteria,like that of the eubacteria,is a single,
circular DNA molecule not contained within a nucleus,but
the size of the DNA molecule is often smaller than that of ￡,
coli.
Genetic material
plasmid
Basic structure
Some bacteria contain structures associated with specialist
functions,Granular structures,called inclusion bodies,can
often be seen under the light microscope,These granules are
usually for storage and may be membrane bound（与膜结合）,such as poly-β-hydroxybutyrate (PHB) granules（聚 β
羟丁酸盐 ）,or found scattered in the cytoplasm,such as
polyphosphate granules多聚磷酸盐颗粒或称为异染粒 (also
called metachromatic granules),Lipid droplets can also be
seen in some bacteria,An interesting inclusion body,the gas
vacuole,is found in Cyanobacteria (blue-green algae) and
other photosynthetic bacteria that live in an aqueous
environment,This protein-surrounded vacuole provides
buoyancy,allowing the bacteria to float near the surface of
the water.
4.7 Inclusion bodies
PHB granules
polyphosphate granules（ metachromatic
granules ）多聚磷酸盐颗粒或称为异染粒
Lipid droplets
gas vacuole
Inclusion bodies
Basic structure
Cell wall
Although bacteria do not have organized intracellular
membranes,invaginations （内陷结构） of the plasma
membrane called mesosomes are often seen in electron
micrographs,There is some debate as to whether these
mesosomes really exist and are not just an artefact（假象）
of the fixation process for electron microscopy,Their
function is thought to be in cell division,possibly in laying
down new cell-wall material（促进新细胞壁的形成） or in
the replication of the chromosome and its subsequent
distribution to daughter cells,
4.8 mesosomes
Basic structure
Other,more specialist and complex,intracellular
membrane systems are found in photosynthetic bacteria,
such as Chloroflexus（绿屈挠菌属） (green non-sulfur
bacteria绿色非硫细菌 ) and Rhodopseudomonas (purple
bacterium),associated with the trapping of light energy,
4.9 intracellular membrane systems
内膜系统
Special structure
Finally,a number of bacteria including mainly the
Bacillus （芽孢杆菌属） and Clostridiwn genera （梭菌属） produce a special reproductive structure（它无繁殖功能，为抗逆性休眠体） called the endospore芽孢,This
can be seen in the light microscope using either specialist
spore stains such as mala chite green （孔雀绿） or by
phase-contrast microscopy,The spore has a number of
layers surrounding the bacterial genetic material making
it incredibly resistant to all kinds of environmental stress
such as heat,UV irradiation,chemical disinfectants and
drying,As a number of important pathogenic bacteria
are spore producers,sterilization measures must
therefore be designed to remove these hardy structures as
some can withstand boiling for several hours,
4.10 sporeSpecial structure
spore
Site
attribute
Bacteria genera having endospore
Structure
Observation
function
revision
Exosporium
（芽孢外壁）
Spore coat
Core wall(核心壁或芽孢壁 )
nucleoid
Cortex(皮层 )
ribosome
core
Diagram of an endospore
A number of features are found on the surface of the bacteria which
aid the survival of the cell in the environment.
Definition Thin hair-like proteinaceous appendages,several
micrometers long,called pili菌毛 (s,pilus) or fimbriae纤毛（伞毛）
(s,fimbria) are often seen projecting from the surface of the cell in
electron micrographs,
Roles
A These structures are normally associated with the adhesion of
bacteria to surfaces ;
B there is one particular type of pilus,the sex pilus,which is involved
in the transfer of genetic material from one bacterium to another,
4.11 Pili or
fimbriaeSpecial structure
Definition Motile bacteria have one or more flagella (s,flagellum)
which are slender纤细,rigid 坚韧 structures up to 20 um long,
Roles Rotation of the flagellum in relation to the cell allows the
movement of the bacterium(鞭毛的旋转与细菌的运动有关 ),Normally,
bacteria move in response to external stimuli; an example of this is
chemotaxis(趋化性 ) when bacteria move towards nutrients or away
from harmful substances as a result of chemical gradients (由于化学梯度的结果 )
flagellaSpecial structure
痢疾杆菌 Shigella sonnei - rod
prokaryote; causes shigellosis
(bacterial dysentery) (x 22,400)
霍乱弧菌 Vibrio cholerae - vibrio-shaped prokaryote that causes cholera (x 15,575)
伤寒杆菌 Salmonella - rod prokaryote ;
note the flagella,Causes salmonellosis
(food poisoning),(x 20,800)
E,coli
The surface of cells are often covered by layers of
polysaccharide or proteinaceous material known as capsules or
slime layers,depending on their density,If it is diffuse (散开的 )and
easily lost it is called a slime layer,The polysaccharide layers are
sometimes called the glycocalyx(糖萼 ),However,some bacteria
have proteinaceous capsules,These layers play a role in
protecting the cell from desiccation and toxic compounds and
also in the adhesion of bacteria to surfaces.
4.12 Capsule or
slime layerSpecial structure
These additional surfaces layers have a number of
functions;
they act as permeability barriers to the cell surface;
(对细菌表面起渗透屏障的作用 )
they protect the bacteria from phagocytosis;
they protect the cell from desiccation;
they aid in the attachment (adhesion) of bacteria to
surfaces.
Role of capsule or
slime
5,The Gram-positive bacteria v.s,the
Gram-negative bacteria
The eubacteria are frequently divided
into two groups on the basis of their
reaction to a stain devised by Christian
Gram in 1884,
The differential reaction to the
staining procedure is because of the
structure of the cell envelope in these
two groups of bacteria,
The Gram-positive bacteria have a single
membrane called the cytoplasmic (or plasma)
membrane,surrounded by a thick layer of
peptidoglycan (20-80 nm),
The Gram-negative bacteria have only a
thin layer of peptidoglycan (1-3 nm) but on
the outside of this there is a further outer
membrane which acts as an additional
barrier,
The procedure is as follows,Fixed cells are stained with a
dark stain such as crystal violet,followed by iodine which
complexes with the stain in the cell wall of the bacteria,
Alcohol is added,which washes the dark stain of crystal
violet-iodine out of cells that have thin cell walls but not
from those that have thick cell walls,Finally,a paler stain
such as carbol fuschin(石炭酸复红 ),called a counter-stain,is
added which stains the decolorized cells pink but is not
seen on the dark staining cells that retained the first stain,
The cells that retain the stain (with thick cell walls) are
called Gram-positive and appear dark purple under light
microscopy,The ones that lose the stain (with thin cell
walls and an outer membrane) are called Gram-negative
and stain pink or pale purple.
The procedure for the Gram stain
5.1 The procedure for the Gram stain
Smear fixing
crystal violet
初染
iodine
媒染
Alcohol
脱色
carbol
fuschin
复染
Crystal violet-iodine
staining washing
E,coli
5.2 Result of Gram-stain
The cells that retain the stain (with thick cell
walls) are called Gram-positive and appear dark
purple under light microscopy,
The ones that lose the stain (with thin cell walls
and an outer membrane) are called Gram-
negative and stain pink or pale purple.
G+
G-
6.reproduction and colony morphological features
Reproduction
Fission
binary fission
equal binary fission
unequal binary fission
trinary fission only pelodictyon(暗网菌属 )
multiple fission only bdellovibro（蛭弧菌）
Budding budding bacteria（芽生细菌）
大肠杆菌裂殖
Colony morphological features
Size
Shape
Texture(油脂状、膜状、粘、脆等 )
Color
transparency（ 透明、半透明、不透明等 ）
Surface situation（ 光滑、皱褶、颗粒状龟裂、同心圆状等）
Upheaval leval（ swell,bulge） 隆起程度（扩展、
台状、低凸状、乳头状）
Surface luster（闪光、不闪光、金属光泽等）
Factors that affects colony feature
Culture time
Colony density
Flagella
Capsule or slime（ glycocalyx 糖被）
Spore
个体形态与群体形态之间存在着明显的相关性：无鞭毛，不能运动的细菌通常都形成较小，较厚，边缘园整的半球状菌落；有鞭毛运动能力强的细菌一般形成大而平坦、
边缘多缺刻（甚至成树根状）、不规则型的菌落；有糖被的细菌，会长出大型、透明、
蛋清状的菌落；有芽孢的细菌往往长出外观粗糙、干燥、不透明的且表面多褶皱的菌落等。
Close corelation between
individual shape and
colony feature
The colony of immotile bacteria always is smaller,thicker,
semi-spherical with round and tidy edges,Otherwise,bacteria
with flagella forms large,flat,nicked or even tree root liked,
irregular colony,
The colony of bacteria with polysaccharide envelope(glycocalyx糖被 ) is always large,transparent and like egg white,
Bacteria having endospore can grow to coarse,dessicant,opaque
colony with draped surface.
Usage
Colony plays important roles in the
following aspects of biological
researches：
Isolation
Purification
Identification
Bacterium counting
Screening and breeding of
microorganism
Bacteria related to food
Acetobacter (醋酸杆菌属 )
Listeria（李斯特氏菌属）
Lactobacillus（乳杆菌属）
Leuconostoc（明串珠菌）
Bifidobacterium（双歧杆菌属）
Bacillus（芽孢杆菌属）
Clostridium（梭状芽孢杆菌）
Micrococcus（微球菌属）
Streptococcus（链球菌）
Staphylococcus（葡萄球菌）
bacteria related to food
Pseudomonas假单胞杆菌属
Achromobacter无色杆菌属
Aicaligenes（产碱杆菌属）
Flavobacterium（黄色杆菌属）
Escherichia and enterobacter（埃希氏杆菌属和肠细菌属）
Salmonella（沙门氏菌）
Proteus（变形杆菌）
Fermentation has been a major way of preserving
food for thousands of years,Fermentation is a
means by which microbial growth causes
chemical and/or textural changes which form a
product that can be stored for extended periods,
The fermentation process is also used to create
new food flavors and odors.（味道和风味）
Fermented foods
Yoghurt is produced by S,thermophilus and L,
bulgaricus,With these organisms growing in
concert（协同生长）,acid is produced by
Streptococcus,and aroma components are
formed by Lactobacillus,Freshly prepared
yoghurt contains 109 g-1 of bacteria,
Dairy products（ 1） —— yogurt
Cheese is another microbial fermentation product,All cheese results
from a lactic acid fermentation of milk,The process requires the growth
of a starter culture（发酵剂，起子） in milk which produces flavor
changes （味变） and acid production,resulting in coagulation of milk
solids and formation of a curd（乳凝块）,Renin（肾素）,an enzyme
from calf stomachs (which can also be produced by genetically
engineered microorganisms),is used to assist in curd formation,The
curd is heated and pressed to remove the watery part of the milk or whey
（乳清）,salted,and then ripened（加上盐，然后便成熟）,The cheese
curd（干酪） can be ripened with or without additional microorganisms,
Cheese curd inoculation is used in the manufacture of Roquefort and
blue cheese.（干酪加曲用来生产法国浓味羊奶干酪和蓝干酪）
Dairy products（ 2） —— cheese
A variety of meat products,especially sausage
（香肠）,can be fermented,country-cured hams
（乡下腌制的火腿）,summer sausage（夏季香肠）,
salami（意大利香肠） and izushi,Pediocqccus
cerevisiae（啤酒片球菌） and L,plan-tarum（植物乳杆菌） are most often involved in sausage
fermentations,Izushi is based on the fermentation
of fresh fish,rice and vegetables by Lactobacillus.
Meat and fish
Bacteria also play a significant role in food
spoilage (detrimental changes to the food),
Foods with easily utilizable carbohydrates,
proteins and fats are ideal environments for
spoilage by microorganisms,
Food spoilage
For examples:
Milk undergoes a series of steps which include
increased lactic acid production by S.lactis（乳链球菌）,growth of more acid-tolerant organisms and
finally protein digestion by bacteria that results in
the formation of a putrid odor（腐臭气味 ） and bitter
flavor,
In canned foods,spoilage is typically caused by
fermentative bacteria such as Clostridia （梭状芽孢杆菌） which alter the texture and taste of the food as a
result of protein degradation,The production of
CO2and H2S during spoilage causes cans to swell,
More importantly the presence of bacterial
pathogens in food presents a significant problem。
Bacterium Disease Foods involved
Food infections
Enteropathogenic ￡,coli (0157) ￡,coli enteritis Cheese,meats
Listeria monocytogenes Listeriosis Dairy products
Salmonella typhimurium Salmonellosis Meats,poultry,
S,enteritidis eggs,dairy products
Vibrio parahaemolyticus V,Parahaemolyticus Seafood
gastro-enteritis
Major diseases and poisonings associated with food
细菌肠道致病菌大肠杆菌单核细胞增生李斯特氏菌鼠伤寒沙门氏菌肠炎沙门氏菌副溶血弧菌疾病大肠杆菌肠炎李斯特菌病沙门氏菌病副融血性弧菌胃肠炎涉及的食物干酪，肉类乳制品肉类，家禽蛋，乳制品，海产品食物感染
Clostridium perfringens Perfringens food poisoning Meats and
产气荚膜梭状芽孢杆菌 产生荚膜食物中毒 poultry
C,BotulinumBotulism botulism Fish,meats and
肉毒梭状芽孢杆菌 肉毒中毒 canned foods
Bacillus cereus B,cereus food poisoning Meats,rice,
蜡状芽孢杆菌 蜡状芽孢杆菌食物中毒 cereals,potatoes
Food poisoning
（ caused by toxin release）
化脓性链球菌
Streptococcus
pyogenes - coccoid
prokaryote; causes
pharyngitis,sinusitis,
otitis media (middle ear
infection),food
poisoning,puerperal
fever (childbed fever),
skin and wound
infections (scarlet fever,
erysipelas,impetigo),
Group A strep,SEM
x56,000
Plastic kitchen cutting board
surface - rod bacteria in a smooth
matrix; filamentous bacteria ( 丝状菌 ) -smooth oval cells; fungal
hyphae ( 真菌菌丝 ) with textured
spores ( 结构孢子 ) (x 2,270)
Rod-Shaped Bacterium,E,coli
(SEM x22,245) E,coli (0157:H7) - a
rod prokaryote,Hemorrhagic type
粪链球菌 Streptococcus
faecalis - coccoid prokaryote;
a pathogen causing skin and
wound infections
Young cells are G_,elder bacteria are always G+,
sporeless,motile or immotile,aerobic,Bacteria of this
genus have strong oxidative ability to oxidize alcohol into
acetic acid,therefore beneficial to acetic acid industry and
detrimental to alcohol beverage,Usually can be found in
fermented foodstuff,decayed fruits and vegetables,sour
wine and juices,For instance:
A.aceti(纹膜醋酸杆菌 ) is responsible for the sour wine and
juices;
A,xyliuum(胶醋酸杆菌 ) and A,suboxydans(弱氧化醋酸杆菌 )
may forms goos(粘性物质 )and impair the production of
vinegar.
Acetobacter
(醋酸杆菌属 )
Immotile,G+ bacillus organized in chains,
can be easily found in milk and plant product
such as L.casei(干酪乳杆菌 ),L.bulgarics(保加利亚乳杆菌 ),L.acidophilus(嗜酸乳杆菌 ),
L.thermophilus(嗜热乳杆菌 ),they are always
used as ferment starter for the making of
following dairy product,yogurt,cheese and
lactic acid,
Lactobacillus
（乳杆菌属）
乳酸杆菌
Salmonella
(沙门氏菌 )
Short,G- peritrichate motile bacillus,don’t
produce pigments on medium,ferment
glucose and other monosaccharides,
produce both acid and CO2(there few
exceptions),but can’t utilize lactose.
It’s an important enteropathogenic bacteria
and cause the infectious diseases and food
spoilage.
沙氏杆菌
Staphylococcus
(葡萄球菌属 )
G+,usually produce contact enzyme,existed
in the nasal cavity and on the skin or other parts
of body,S,aureus don’t produce pigments or
contact enzyme either,causing abscess and
wound pyogenesis,can produce enterotoxin
thus causing food poisoning.
Escherichia
( 埃希氏菌属 )
Short peritrichate bacillus,G-,hard to discriminate it
with enterobacter(肠杆菌属 ) under light microscopy
and on the medium,Both of them belong to coliform
group(大肠菌群 ),citrate can’t be used as the only
carbon source.
The members mainly exist in the animal or human
intestines,distributed in water and soil,Animportant
saprobe(saprophytes腐生菌 ) in food,If a mount of E,
coli are found in food,this indicates that the food has
been contaminated by manure,So there is strict
stipulation of the number of E,coli for food such as
water,milk and unheated beverages.
肠杆菌
E。 coli
E。 coliE。 coli
Bacillus
(芽孢杆菌属 )
G+,aerobic spore-producing bacillus,widely
existed in the environment,especially in the
soil and air,bacillus anthrax (炭疽芽孢杆菌 )of this
genus is a devastating pathogen which cause
anthracnose （炭疽病）,Other bacteria of this
genus usually cause the food spoilage such
as bacillus subtulis(枯草芽孢杆菌 ) and Bac,
Mycoides(蕈状芽孢杆菌 ),
芽孢杆菌炭疽杆菌炭疽杆菌炭疽杆菌
Section C Actinomyces
Definition,A group of filamentous Gram positive
bacteria reproduced by the formation of spores.
(为一类主要呈丝状生长和以孢子繁殖的革兰氏阳性细菌 )
Distribution,widely existed in the dry,a little alkaline
soils rich in organic materials,Geosmin produced by
actinomyces endow the mud with specific smell.
(广泛分布在含水量较低、有机物较丰富和呈微碱性的土壤中。泥土所特有的泥腥味，主要由防线菌产生的土腥味素所引起。每克土壤中防线菌孢子数可达 107个 )
炭疽杆菌
G+ anaerobic or slightly aerobic,spore-producing
bacillus,among them pathogen of Bacillus
clostridium ( 肉毒梭状芽孢杆菌 )are extremely
poisonous,Cl,Thermosaccharolyticum (热解糖梭菌 )
is obligate thermophilus bacterium catalyzing
saccharides,therefore is responsible for the
deterioration of canned fruits or vegetables,
Cl.putrefaciens(腐化梭菌 ) usually cause the spoilage
of proteinaceous food.
Clostridium
(梭状芽孢杆菌属 )
N o n a m e,t x t
放线菌与人类的关系极其密切，绝大多数属有益菌，对人类健康的贡献尤为突出。至今已报道过的近万种抗生素中，约
70％由放线菌产生；近年来筛选到的许多新的生化药物多数是放线菌的次生代谢产物，包括抗癌剂、酶抑制剂、抗寄生虫剂、
免疫抑制剂和农用杀虫 (杀菌 )剂等。放线菌还是许多酶、维生素等的产生菌。 Frankia(弗兰克氏菌屑 )对非豆科植物的共生固氮具有重大的作用。此外，放线菌在甾体转化、石油脱蜡和污水处理中也有重要应用。由于许多放线菌有极强的分解纤维素、
石蜡、角蛋白、琼脂和橡胶等的能力，故它们在环境保护、提高土壤肥力和自然界物质循环中起着重大作用。只有极少数放线菌能引起人和动、植物病害。
1.morphology
Substrate mycelium
Aerial mycelium
Spore-bearing mycelium
放线菌
Aerial mycelium
twist Spore-bearing mycelium
conidium
Substrate mycelium
medium
annulus spore-
bearing mycelium
Streptomyces has the most typical
morphological features and is the most
closed to human life,
Diagram of streptomyces(链霉菌 )
Morphology of spore-bearing mycelium(streptomyces)
Nocardia 诺卡氏菌属 Micromonospora
Microbispora
Microtetraspora
Micropolyspora
Streptosporangium
Actinoplanes
pirillospora
The colony is constituted by mycelium,Slender hyphae of the
actinomyces grows slowly and interweaved,thus lead to the small,
wrinkled colony with tight texture and dry surface,The substrate
mycelium grows into the medium,so the colony tightly attached to it,
hence it’s hard to pick it up with innoculating loop,At the very
beginning of the formation of the colony,it’s similar with that of
bacterial,because the aerial mycelium has not differentiated into
spore-bearing mycelium yet,When a large amount of spores have
been produced and spreaded on the surface of colony,the typical
irradiative,fine powder -liked or granular colony was formed.
Colony features
分生孢子：最常见，如 streptomyces等大多数种类借孢子孢囊孢子基内菌丝断裂：如 Nocardianocardia (诺卡氏菌属 )
借菌丝任何菌丝片段：各种放线菌
reproduction
Actinomyces in food
Scarcely can actinomyces cause the spoilage
and deterioration of food,Only one genus might
endanger the safety of it——Streptomyces(链霉菌属 ),The members of this group contaminate
vegetables via soil,they also exist in man’s mouth,
Some species can cause the plant disease at room
temperature.
Section D Other prokaryotes
Cyanobacteria ever called blue algae or blue-green
algae is a group of large visible prokaryotes which is
Gram-negative,flagellaless,with chlorophyl while
without chloroplast,and can photosynthesize the
oxygen.
Cynobacteria has a long evolving history and
widely exists in the environment such as water
bodies of all kinds,soil,internal or external of some
living creatures,even on the rock surface or other
adverse environment can also find them,so they are
famed as ―pioneer organism”
绿藻蓝细菌
（
螺旋藻
）
蓝细菌
（
鱼腥草
）
旧名蓝藻（ blue algae）或蓝绿藻（ blue-green algae），是一类进化历史悠久,G阴性、无鞭毛、含叶绿素 a（但不形成叶绿体）、能进行产氧性光合作用的大型原核生物。蓝细菌广泛分布与自然界，包括各种水体、土壤中和部分生物体内外，甚至在岩石表面和其他恶劣环境中都可找到他们的踪迹，因此有,先锋生物,之美称。他的发展使整个地球大气从无氧状态发展到有氧状态,从而孕育了一切好氧生物的进化和发展,在人类生活中,蓝细菌有着重大的经济价值,有许多食用种类,目前已开发成有一定经济价值的螺旋藻产品,至今已知有 120多种蓝细菌具有固氮能力,特别是与满江红鱼腥蓝细菌共生的水生蕨类满江红,是一种良好的绿肥,some cynobacteria are responsible for the ―赤潮,of
sea water and ―水华,of lake.
Chlamydia is a group of G-,obligate energy parasite(专性能量寄生 ) prokaryotes,They have the following features:
1,Cell structure
2,Both have RNA and DNA
3,Have cell wall (but without peptidoglycan)
4,Have ribosome
5,Lack energy-producing system,obligate intracellular
parasite
6,Sensitive to antibiotics and medicine that inhibiting
bacteria
7,Reproduce by binary fission
8,Only can be cultured within living eukaryotic cell
Chlamydia (衣原体 )
Mycoplasma is the smallest prokaryote
without cell wall between independent living
and intracellular parasite,Many species are
pathogens of animal and human,
Mycoplasm
(支原体 )
Features of mycoplasma
The cell is so small that nearly can’t be seen
under the light microscopy.
The membrane is rigid than other
prokaryotes in that contains sterols.
Without cell wall therefore sensitive to
osmotic pressure and insensitive to the
antibiotics that inhibiting the synthesis of the
cell wall,so gram stain is negative and
without fixed shape.
(continued)
Colony is small and looks like oil fried
egg.
reproduce by binary fission and
budding.
Although fastidious,can grow on the
special mediums.
Most of them can utilize saccharide as
carbon source,aerobic or anearobic,
Small genome.
Named after H.T.Ricketts,an American doctor
who firstly discovered the pathogen for 落基山
ship fever(船热，斑疹伤寒 ),and lose life
because of infection by accidence,Rickettsia is
a group of obligate parasite G- prokaryotes.
The feature of it distinguished with cytoplasm
is that it has cell wall and can’t live
independently,distinguished with chlamydia,its
cell is larger and has energy-producing system,
Rickettsia
(立克次氏体 )
Rickettsia
and function of prokaryotes
原核生物的形态，结构和功能
Prokaryotes and eukaryotes
major differences
section A
Within the microbial world can be found two
different categories of cell type/ prokaryote
and eukaryote,
DNA free in the cytoplasm
Only one chromosome
DNA associated with
histone-like proteins
May contain
extrachromosomal
elements called Plasmids
Introns not found in mRNA
Cell division by binary
fission - asexual replication
only
Transfer of genetic
information occurs by
conjugation,transduction
and transformation
DNA is contained with a membra-
ne bound nucleus,A nucleolus is
also present
>1 chromosome,Two copies of
each chromosome may be present
(diploid)
DNA complexed with histone
proteins
Plasmids only found in yeast
Introns found in all genes
Cells divide by mitosis
Exchange of genetic information
occurs during sexual reproduction,
Meiosis leads to the production
of haploid cells (gametes) which
can fuse
原核生物和真核生物遗传的和细胞组装上的主要差别
DNA在细胞质中游离
只有一个染色体
DNA与类组蛋白连系
含有染色体外的遗传物质，称为质粒
在 mRNA中没有发现内含子
细胞分裂以二等分裂方式，只有无性繁殖
遗传信息传递可通过接合、转导、转化发生
DNA在膜包围的核中，只有一个核仁
多于一个染色体，每个染色体是双拷贝 (双倍体 )
DNA与组蛋白连系
只在酵母中发现质粒
所有基因中都发现内含子
细胞分裂为有丝分裂
遗传信息交换发生在有性繁殖过程，减数分裂导致产生
单倍体细胞 (配子 )，它们能融合
.原核生物,真核生物遗传物质的组装和复制
1,Cytoplasmic membrane contains hopanoids lipopoly-
saccharides,and teichoic acids found
2,Energy metabolism associated with the cytoplasmic
membrane
3,Photosynthesis associated with membrane systems and
vesicles in cytoplasm
4,Flagella consist of one protein,flagellin
5,Ribosomes - 70S
6,Peptidoglycan cell walls (eubacteria only:different polymers
in archaebacteria)
Cellular organization of
prokaryotes
1,Cytoplasmic membrane contains sterols
2,Mitochondria present in most cases
3,Chloroplasts present in algal and plant cells
4,Internal membranes,endoplasmic reticulum and Golgi
apparatus present associated with protein synthesis and
targetting
5,Membrane vesicles such as lysosomes and peroxisomes
present
Cellular organizaton
of eukaryotes
6,Cytoskeleton of microtubules present
7,Flagella have a complex structure with 9+2
microtubular arrangement
8,Ribosomes – 80s(mitochondrial and
chloroplast ribosomes are 70S)
9,Polysaccharide cell walls,where present,are
generally either cellulose or chitin
质膜含有 hopanoids、脂多糖和磷壁酸
能量代谢与细胞质膜连系
光合作用与细胞质中膜系统和泡囊连系
由一根蛋白鞭毛丝构成鞭毛
核糖体 ——70S
肽聚糖的细胞壁 (只有真细菌有，古细菌中是不同的
多聚体 )
质膜含有固醇
多数情况在线粒体中发生
藻类和植物细胞中存在叶绿体
蛋白质合成和定向运输与内膜、
粗面内质网及高尔基体有关
有膜囊泡如溶酶体和过氧化物酶体有微管骨架
核糖体 ---80S，细胞壁多糖一般是纤维素或者是几丁质细胞组装
Rough ER
Golgi
mitochondria
Choloroplast
Cell wall of eukaryote
细胞核示意图
Nuclear spore
chromatin
cytoskeleton
一切真核细胞都有一套由蛋白质丝组成的细胞内部骨架。它不仅有助于细胞内部活动的条理化，并且是细胞运动及形态变化的基础。
Cytoskeleton of cultured cell
肌动蛋白丝微管中间丝当一个细胞分裂时，其核膜被解离，且其 DNA浓集成可见的染色体对，它们被微管拉开至两个分裂的自细胞中，微管从分裂细胞相对的两极会聚点辐射出去。
一个正在分裂的细胞中的微管
Lysosome——a kind of organelle in animal cell
A comparison of the main features of these
two categories of cell is shown in the table
discussed,but other differences do occur,
Although the basic mechanisms of DNA
replication,RNA synthesis and protein
synthesis are the same in both prokaryotes and
eukaryotes,there are differences in the
components and enzymes involved,These are
discussed in the appropriate topics.
Major groups of prokaryotes
bacteria
actinomyces Cyanobacteria
Spirochetes
others Rickettsia
Chlamydia
Mycoplasmas
杆菌原核生物常见种类和常见形态（ 1）
球菌原和生物常见种类和常见形态（ 2）
蓝细菌（螺旋藻）
蓝细菌（鱼腥草）
原和生物常见种类和常见形态（ 3）
古细菌（产甲烷细菌） 细菌（耶尔森鼠疫杆菌）
Bacteria are small (< 1um-50um width/diameter),
single-celled,micro organisms that belong to a group
called prokaryotes so classified because their DNA is
not enclosed within a nuclear membrane,
definition
Section B bacterium
Because they lack,a distinct nuclear
membrane,the organelles associated with
energy generation,such as mitochondria
and chloroplasts,and complex internal
membranes,such as endoplasmic
reticulum and Golgi apparatus,which are
found in eukaryotes.
Why bacteria are prokaryotes?
They are a highly successful and diverse
group of organisms that can obtain energy and
carbon from a wide range of sources and
therefore can colonize（定居） every niche on
our planet from deep ocean trenches to
volcanic craters,
Bacteria are ubiquitous
In the 1970s,using DNA sequencing information,it
was found that the group we know as the bacteria
could be split into two,the eubacteria (Gr,eu,true and
bakterion,a small rod) and the archaebacteria (Gr,
Archaios,ancient) and it appears that these two groups
evolved away from each other very early in the history
of living things at about the same time that the first
group of eukaryotic cells evolved,（ 是一个在进化途径上很早就与真细菌和真核生物相互独立的生物类群 ）
1,eubacteria and archaebacteria
On the basis of 16S RNA sequences,it is now clear that there
are (at least) three domains of organisms,the two prokaryotic
groups,archaebacteria and eubac-teria and the eukarya (Fig),
Within the eubacteria there are at least 11 groups,referred to
sometimes as phyla,which can be represented on a phylogenetic
tree,What can be seen is the wide diversity within the bacterial
world and that may be familiar to us such as E,Coli,bacillus
species are located within just a few of these phyla,It should be
noted that the number of phyla will increase as more bacteria
from diverse habitats are sequenced.
An overview of the phytogeny of the living world,showing the three major
domains of organisms,the Eubacteria,the Archaebacteria and the Eukarya,
a Members of the eubacteria include some of the
more familiar bacteria such as Escherichia coli and
Staphilococcus aureus and are the prokaryotes that
are best studied and understood,
The archaebacteria are a very diverse group of organisms,
which differ from the eubacteria in a number of features havi-ng,
in particular,very different cell walls and membranes,This g
roup includes bacteria that are capable of existing in extreme
environments,such as hot springs (examples,Sulfolobus and
Pyrococcus) and high salinity (Halobacterium),and the meth
anogens such as Methobacterium,which produce methane as a
result of metabolism.主要包括一些独特生态类型的原核生物，如产甲烷菌及大多数的嗜极菌（ extremophile），包括极端嗜盐菌、极端嗜热菌和热原体属（ Thermoplasma）
古细菌（产甲烷细菌）
A list of the types of characters used to distinguish
between bacteria is given below,This is not an
exhaustive list and equally not all characters are used in
either the classification or identification of every
bacterial species,In many cases of well known
microorganisms,a small set of tests may be all that is
required to identify a microbe positively,especially if
the site from which it has been isolated and the disease
it caused are known,
Characters used in bacterial identification
A comma-shaped,Gram-negative rod
isolated from a patient excreting copious
amounts of straw-colored,liquid stools may be
enough to identify it putatively as Vibrio cholera,
the causative agent for cholera,However,it may
be necessary to do a wide range of tests to
determine the name of an isolate if it is an
undescribed microbe.
The shape,texture and color of bacterial
colonies can be distinctive,For example,
Staphylococcus aureus is so named as
colonies are of a yellow color; 'aureus' comes
from the Latin for golden.
1.Colony morphology.
Whether bacteria are Gram-positive or Gram-negative is one
of the most important clinical diagnostic tests,Gram staining
and microscopic examination of bacteria give information as to
the shape,size and arrangement of the bacterial cells and in
some cases this is enough to identify certain genera such as
Streptococci which are Gram-positive cocci that grow in chains,
Stains may also be used to show other morphological features,
which may be used for classification,such as the presence of:
spores (malachite green stain);
unusual cell walls (Ziehl Neelsen acid-fast stain);
capsules (Indian ink stain);
intracellular lipids (Sudan black);
flagella (flagellar stain);
metachromatic granules (Albert-Leybourne stain).
2.Cell shape,structures and reaction to stains
The temperature,pH and 0;
requirements of an isolate are
useful tests for the identification of
bacteria.
3.Growth characteristics.
There is a wide range of tests available that
measure various aspects of bacterial metabolism:
what carbon and nitrogen sources the bacteria
can use;
the end products of their metabolic processes,
such as acetoin,tested for in the Vogues-Proskaeur
test;
what enzymes the bacteria produce,such as
decarboxylases,proteases and DNases;
the presence of other molecules such as toxins,
long- chain fatty acids or antibiotics.
Biochemical tests
Antibodies to cellular components such as
the 0-side chains of lipopolysaccharide (LPS)
(Topic D3) or capsules are frequently used to
distinguish between strains of one species.
Immunological tests
Comparisons of DNA content and sequence between strains
are the most definitive methods for separating organisms into
different groups and for measuring the evolutionary
relatedness between them (phylogenetic analysis),Traditionally,
DNA was analyzed by measuring the G-C content or the amount
of DNA homology between strains,More recently,the
comparison of the actual DNA sequences of conserved cellular
molecules such as 16S ribo-somal RNA or proteins such as
cytochrome C,ATPase and elongation factor has been used,
This information has been analyzed by a tech nique called
cladistics to trace true phylogenetic lineages that have not been
obscured by patterns of convergent evolution,
DNA tests
The main impetus for bacterial classification has been
the need to be able to identify bacterial disease-causing
organisms and therefore these microbes are particularly
well classified,However,it should be remembered that
many other species have not been well characterized
and many have not been isolated or described at all,
The authority on bacterial classification is Bergey's
Manual of Systematic Bacteriology,which contains as
near as possible complete listings of all prokaryotic
species and their distinguishing characteristics.
Classification of bacteria
ranked are,sequentially,family,order,class,division
and kingdom,though the final three are not particularly
useful in bacteriology,Similarly,species may be divided
into subspecies and a culture of a particular organism
is usually referred to as a strain,Strain is also used to
describe a sub-group of a species that share some
feature such as one type of 0-antigen or mutation,
There are also informal names,not italicized,which are
sometimes useful for describing groups of organisms
such as the green-sulfur bacteria or the spiro-chetes.
Classification of bacteria
In spite of this simplicity in structure there is
a large amount of variation in the appearance
of the cells when observed under the microscope,
Two shapes of cell predominate,the coccus
(spherical) and the bacillus,or rod,but there
are also a wide range of other shapes
(morphologies)
2.Bacterial shapes
2.1 Individual
shapes
Organization of cells Examples
Cocci In chains Streptococcus
spherical bacteria In grape-like clusters Staphylococcus
In pairs (diplococci) Neisseria
In cubes of cells (packets) Sarcina
single Micrococcus ureae
（ 1） coccus
球菌 (coccus)
脑膜炎奈瑟菌双球菌 (diplococcus)
肺炎链球菌链球菌 (streptococcus)
球菌 (coccus)
球菌 (coccus)
葡萄球菌 (streptococcus)
球菌 (coccus)
四联球菌 (tetrad)
球菌 (coccus)
八叠球菌 (sarcina)
杆菌 (bacillus)
不同杆菌的大小、长短、粗细很不一致。
炭疽芽胞杆菌 3-10 μ m
大 中大肠埃希菌 2-3 μ m
小布鲁菌 0.6-1.5 μ m
杆菌的形态多样杆菌 (bacillus)
两端齐平炭疽芽胞杆菌两端尖细白喉棒状杆菌杆菌 (bacillus)
杆菌的形态多样分枝杆菌 双歧杆菌螺形菌 (spiral bacterium)
弧菌 螺菌 螺杆菌化脓性链球菌
Streptococcus
pyogenes - coccoid
prokaryote; causes
pharyngitis,sinusitis,
otitis media (middle ear
infection),food
poisoning,puerperal
fever (childbed fever),
skin and wound
infections (scarlet fever,
erysipelas,impetigo),
Group A strep,SEM
x56,000
粪链球菌 Streptococcus
faecalis - coccoid prokaryote;
a pathogen causing skin and
wound infections
链球菌
Rods/bacilli - rods may be very short (cocci-bacilli) or long
Singly Pseudomonasa
In filaments of attached cells Bacillus sp.
Most bacteria used in industry are bacillus
Bacillus subtilis to produce,amylase and protease
Coroynebacterium pekinense used for glutamic acid
Lactobacillus bulgaricus used in milk industry
（ 2） bacillus
结核杆菌 Mycobacterium
tuberculosis,Rod-shaped
Bacterium (SEM x40,000)
白喉杆菌 Corynebacterium
diphtheriae,Rod,clubed-
shaped Bacterium (causes
diphtheria)
Plastic kitchen cutting board surface -
rod bacteria in a smooth matrix;
filamentous bacteria ( 丝状菌 ) -smooth
oval cells; fungal hyphae ( 真菌菌丝 )
with textured spores ( 结构孢子 ) (x
2,270)
Rod-Shaped Bacterium,E,coli (SEM
x22,245) E,coli (0157:H7) - a rod
prokaryote,Hemorrhagic type
痢疾杆菌 Shigella sonnei - rod
prokaryote; causes shigellosis
(bacterial dysentery) (x 22,400)
伤寒杆菌 Salmonella - rod prokaryote; note the flagella,Causes
salmonellosis (food poisoning),(x
20,800)
大肠杆菌棒状杆菌肠杆菌
Comma shaped - called a vibrio Vibrio
Spirillum - long,curved,rigid rods Rhodospirillum
A Tightly coiled flexible bacteria –spirochaetes Treponema 柔软易曲的紧螺旋 如：密螺旋体属 Rhodospirillum
疏螺旋体属 Borrelia
B Appendaged - cells have stalk or tube-like extensions
如红微菌属 Rhodomicrobium
C Pleomorphic - bacteria vary in shape
如棒杆菌属 Corynebacteria
D Branching mycelium-like filaments Streptomyces
（ 3） spirillum and vibrio
（ 4） others
霍乱弧菌 Vibrio cholerae - vibrio-
shaped prokaryote that causes
cholera (x 15,575)
Bdellovibrio bacterovorus
它有一条端生鞭毛，这种细菌攻击并杀死比它更大的细菌且以其为食物。
螺旋杆菌 Spirochete bacteria
红弧菌螺菌螺旋菌
Measure Unit,um
Description：
Bacillus ——width× length （ 0.20~1.25） × （ 0.300~8.00)
Spirillum——width× length （ 0.3~1.0） × （ 1.0~5.0）
Coccus—— diameter 0.20~1.25
3,size of bacteria
Basic structure
Cell wall
Cytoplasmic
membrane
Mesosome
Protoplast
Nucleus
Ribosome
Inclusion body
Special structure
Flagella
Capsule
spore
4,structure
细菌的结构基本结构 细胞壁、细胞膜、细胞质、核质特殊结构 荚膜、鞭毛、菌毛、芽胞一,基本结构
（一）细胞壁 (cell wall)
革兰阳性菌革兰阴性菌革兰染色两类细菌细胞壁的共同组分为肽聚糖，但各有其特殊组分。
革兰染色法：
涂片 风干 固定结晶紫 碘液 95%乙醇 复红1min 1min 脱色
1,肽聚糖 (peptidoglycan)
革兰阳性菌肽聚糖 — 聚糖骨架、四肽侧链、五肽交联桥青霉素作用点溶菌酶作用点
N-乙酰葡糖胺
N-乙酰胞壁酸革兰阴性菌肽聚糖 — 聚糖骨架、四肽侧链
1,肽聚糖 (peptidoglycan)
2,革兰阳性菌细胞壁特殊组分壁磷壁酸膜磷壁酸
3,革兰阴性菌细胞壁特殊组分
3,革兰阴性菌细胞壁特殊组分脂多糖 (lipopolysaccharid,LPS)
革兰阳性菌与阴性菌细胞壁结构比较细胞壁 革兰阳性菌 革兰阴性菌强度 较坚韧 较疏松厚度 20-80nm 10-15nm
肽聚糖层数 可多达 50层 1-2层肽聚糖含量 占细胞壁干重 50%-80% 占细胞壁干重 5%-20%
磷壁酸 + —
外膜 — +
脂蛋白 — +
脂多糖 — +
维持菌体固有的形态
保护细菌抵抗低渗环境
参与菌体内外的物质交换
菌体表面带有多种抗原分子，可诱发机体的免疫应答。
4,细胞壁的功能
Fig,1,Diagram of a prokaryote cell (Gram-negative).
4,structure
pilus
细菌细胞的透射电子显微镜照片及模式图
Their internal cell structure is simple,most of
the cellular complexity associated with the cell
surface structures,Bacteria lack mitochondria
and chloroplasts（叶绿体）,the organelles
associated with energy production in eukaryote
cells and internal membrane structures such as
the endoplasmic reticulum and Golgi apparatus,
although some photo-synthetic bacteria do have
internal membranes.
The cytoplasm of all bacteria is enclosed within
a plasma (cytoplasmic) membrane external to which,
in most cases of eubacteria,is a rigid cell wall made
up of sugars and amino acids called peptidoglycan,
The role of the cell wall is to protect the cell from
lysis resulting from osmotic pressure and it also
gives shape to the cell.
4.1 Cell wall
Some bacteria,the mycoplasma,do not have cell walls
and therefore are unable to survive outside an animal
host which provides it with the right osmotic
environment,Gram-negative bacteria have an additional
outer membrane（外膜又称外壁层 ） containing LPS,
External to this may be other layers of poly-saccharide
or protein making up a capsule or slime layer,Layers
external to the cell wall may be referred to as the cell
envelope细胞外膜,The structure of the eubacterial cell
envelope is discussed in more details.
summerize
1.Position,cytoplasm——cytoplasmic membrane—
—cell wall——（ out membrane） ——cell envelope
（ capsule or slime）
2.Major Function,The role of the cell wall is to protect
the cell from lysis resulting from osmotic pressure and
it also gives shape to the cell.（固定细胞外形和提高机械强度，使其免受渗透压等外力的损伤 ）
3.Composition：
G+ peptidoglycan,teichoic acid（磷壁酸）
G- peptidoglycan,lipopolysaccharide（ LPS）,outer
membrane proteins
Outside the plasma membrane is the cell wall made of
sugars and amino acids called the peptidoglycan (sometimes
called the murein layer),The role of the cell wall is to
provide rigidity and strength,preventing the cell from
osmotic lysis when placed in dilute environments,The
structure of peptidoglycan from E,coli is shown in the
following slide,It consists of long polymers of two sugar
derivitives,NAG and NAM with side chains of four
alternating D- and L-amino acids attached to the NAM,
Rigidity is achieved by crosslinks between the amino acid
chains; normally from the third amino add in one chain to the
fourth amino acid in another chain,The nature of the amino
acid side chains,and the links that join them,vary between
bacterial species; however,the third amino acid is always a
diamino acid (has two amino groups,so can form links) and
the fourth amino acid is normally D-alanine (D-Ala),
Fig,3,Structure of the E,coli peptidoglycan showing
crosslinks between two strands,NAG,N-acetyl-
glucosamine,NAM,N-acetylmuramic add,D-Ala,D-
alanine,DAP,rrieso-diaminopimelic acid; D-Glu,D-
glutamic
In E,coli and most other Gram-negative bacteria
there is a direct link between the diamino acid meso-
diaminopimelic acid（内消旋二氨基庚二酸 DAP） and
D-Ala,In Gram-positive bacteria the linkage often
contains a bridge of amino acids,for example,in
Staphylococcus aureus there is a five amino acid
(pentapeptide) bridge of glycines between D-Ala and L-
lysine,Multiple crosslinks within and between chains
makes peptidoglycan a very strong and rigid structure,
There are several unique features of
peptidoglycan including:
the presence of NAM; this sugar is not found in
eukaryotic cells;
the presence of D-amino acids; L-amino acids are
normally found in proteins.
These features make the peptidoglycan a target for
antimicrobial agents that destroy prokaryotic cells specifically,
but do not harm eukaryotic cells; an example of this is the
antibiotic penicillin,Lysozyme,a natural antibacterial agent
found in tears and natural secretions,breaks down the
linkage between NAM and NAG（散架）,
Removal of the cell wall under conditions where the
osmolarity of the medium is the same as the inside of
the cell (isotonic solution) results in the formation of
round protoplasts原生质体 (Gram-positives) or
spheroplasts 球质体 (Gram-negatives) which survive
as long as the isotonicity is maintained,These
structures lyse,however,if placed in a dilute medium,
illustrating the importance of peptidoglycan to the
cells‘ survival.
Gram-positive cell walls also contain large amounts of
another polymer,called teichoic acid,made up of glycerol
or ribitol joined by phosphate groups,D-Ala,glucose or
sugars may be attached to the glycerol or ribitol and the
poly mers are attached either directly to the NAM in the
peptidoglycan or to lipids in the membrane (in this case
they are called lipoteichoic acids),The function of these
molecules is unclear but they may have a role in
maintaining the struc ture of the cell wall and in the
control of autolysis.
Nocardia诺卡氏菌属,contain waxy esters of
Cell walls of a number of genera including
Mycobacterium(分支杆菌属 ),
Corynebacterium (棒状杆菌 )
and mycolic acids(分枝菌酸 ),which are
complex fatty acids.
One of the distinctive features of archaebacteria is the
nature of the lipids in the plasma membrane which,unlike
the ester-linked lipids of eubacteria and eukaryotes are
ether-linked to glycerol,They are also long chained and
branched,Archaebacterial cell walls and envelopes show
great diversity and complexity in structure,They do not
contain peptidoglycan although some do have a similar
compound called pseudomurein(假肽聚糖 ) which contains N-
acetyl-alosaminuronic acid in place of muramic acid,
Another common type of cell wall is the S-layer,a two-
dimensional,paracrystalline,array of| protein or
glycoprotein on the cell surface,Others have thick
polysaccharide walls outside their plasma membrane.
Archaebacterial cell wall and surface
The plasma membrane is a semi-permeable lipid
bilayer which acts as a barrier between the cytoplasm
and the surrounding environment,The membrane is
made of phospholipids,such as phosphatidyl choline
（磷脂酰胆碱）,which consist of a polar headgroup
attached via glycerol to two long chains of non-polar
fatty acids,Such molecules which consist of both polar
and non-polar groups are called amphipathic（两性分子）,
4.2 Cell membrane
The polar headgroups are hydrophilic
(Gr,hydro,water;philic,loving) and the
fatty acids are hydrophobic (Gr,
phobis,hating) which means that in an
aqueous environment these molecules
line up to ensure that the polar
headgroups are associated with the
water molecules and the hydrophobic
chains are tucked away in the interior
of the bilayer away from the water,
Hence,a bilayer can be formed,called
a membrane,about 5-10 nm thick,
The interior of the membrane is highly hydrophobic,
therefore acting as a barrier to anything that is bulky,such as
glucose,or highly polar,such as ions,Small molecules like
water can diffuse through and hydrophobic compounds such
as benzene(苯 ) can also move through by dissolving in the
hydrophobic interior,Bacterial membranes do not contain
sterols(固醇 ) such as cholesterol which provide stiffness in
higher organisms(高等生物中维持细胞膜稳定的胆固醇 ),
However,recently it has been shown that sterol-like
molecules called hopanoidsare found in bacterial membranes
Embedded in the lipid bilayer are proteins of various
functions including transport proteins,proteins involved in
energy metabolism and receptor proteins that can detect and
respond to chemical stimuli,Integral proteins are those that are
fully associated with the membrane and may penetrate all the
way through,These proteins therefore contain hydrophobic
amino acids in the regions which are buried in the lipid,
Peripheral proteins are ones that are only loosely associated by
charge interactions with the positively charged polar
headgroups of the phos-pholipids or on integral proteins and
can be removed from purified membranes by washing with salt
solutions,
The lipids and proteins are fully mobile and move in relation to each
other,This widely accepted model of membrane struc ture is called
the fluid mosaic model,
Hydrophillic
region
Diagram of the structure of the plasma membrane.
Hydrophobic
region
Hydrophilic
region
Polar
headgroup
Fatty acid
chains
phospholipid
Peripheral protein
Integral protein
The outer membrane of Gram-negative bacteria is made up of
phospholipids(磷脂 ) but it also contains some unique features,
Pores formed by proteins called porins(孔蛋白 ) such as OmpF
and OmpC that allow the passive diffusion of small molecules into
the periplasmic space(周质空间 ).
An abundant small lipoprotein called Braun‘s lipoprotein(布朗脂蛋白 ) that is covalently bound to the peptidoglycan and is
embedded in the outer membrane by its hydrophobic lipid,
therefore holding the peptidoglycan and outer membrane close
together.
LPS molecules are found in the outer leaflet of the outer
membrane projecting into the surrounding medium.(LPS分子位于外膜的外叶伸向周围的培养基中 )
4.3 outer membrane
Porin(trimer)
Braun’s
lipoprotein
O-specific sidechain
LPS
Lipid A
peptidoglycan
Diagram showing the structure of the outer membrane
of a G- bacterium
1.The outer membrane of Gram-negative bacteria acts as an
additional barrier protecting the peptidoglycan from toxic
compounds such as lysozyme which act on the cell wall,
2,It creates an aqueous space between the two membranes
called the periplasmic space which is thought to have a gel-
like structure with a loose network of peptidoglycan running
through it,Estimates as to the width of the peptidoglycan
vary from 1-71 nm but it has proved to be difficult to obtain a
real definitive value,
Role of the outer
membrane
transport of nutrients into the cell;(营养物的运输 )
enzymes that are involved in nutrient
acquisition such as proteases;
enzymes that defend the cell against toxic
chemicals such as β-lactamases that destroy
penicillin.(细胞防御有毒化合物 )
The periplasmic space contains a range of
proteins associated with:
In Gram-positive cells these enzymes (called
exoenzymes) are normally secreted into the
surrounding medium,The presence of the outer
membrane in Gram-negative bacteria allows the
cell to keep the enzymes close to itself rather,than
losing them into the medium.
Lipid A which is embedded in the membrane.
A core polysaccharide which contains a number of
unusual sugars including 2-keto-3-deoxyoctonate (KDO).
A side chain of repeating sugars called the 0-antigen or
0-side chain,The composition of the 0-side chain varies
between strains and antibodies to the 0-antigen are often
used for typing bacteria in the laboratory.
LPS consists of three parts:
they cause a net negative charge on the surface of the cell;
they may hinder the access of toxic molecules to the surface of
the cell there fore play a protective role ;
the long side chains are capable of variation in structure therefore
may play a role in allowing Gram-negative bacteria to evade the
immune response,
Most importantly,the lipid A portion of the LPS molecule is highly
toxic to mammals,Called endotoxin,its presence in the blood
stream,even at very low concentrations,leads to toxic shock and
death,
LPS is responsible for a number of features
of the Gram-negative bacterium:
The cytoplasm of bacteria is aqueous,
containing a cocktail of molecules,
ribonucleic acid (RNA) and proteins
necessary for the cell functions,
Basic structure
4.4 cytoplasm
A The main structures,common to all bacteria,found in the
cytoplasm are the ribosomes,
B The ribosomes which consist of a small and a large subunit,
made up of a complex of proteins and RNAs,
C are the sites of protein synthesis in the cell,
4.5 Ribosomes
Basic structure
The ribosomes in prokaryotic cells,although similar
in shape and function to those of eukaryotic cells,are
different in the nature of the proteins and RNAs that make
up their structure This has proved to be very useful to the
human population as antibiotics that act by inhibiting
protein synthesis in bacteria are not effective against
eukaryotic protein synthesis,thus allowing selective
toxicity,
ribosome
Archaebacterial ribosomes are the same size as those of the
eubacteria but,in some features,they are similar to eukaryotic
ribosomes in that they are resistant to the antibiotics,streptomycin
and chloramphenicol,and sensitive to the action of diphtheria toxin
Basic structure
Bacterial DNA is located within the cytoplasm,It
consists of a single chromosome which varies in size
between different species of bacteria (the E,coli
chromosome is 4 x 106 base pairs long),The DNA is
circular,tightly supercoiled（致密超螺旋） and
associated with proteins which are similar to the histone
proteins found in eukaryotic cells Although the
chromosome is not contained within a nuclear membrane,
it is often seen as a discrete （分离的） area within the
cell in electron micrographs which may be referred to as
the nucleoid.
4.6 Genetic material
nucleoid
Basic structure
Some bacteria also contain small molecules of extra-
chromosomal DNA called plasmids,These often carry
genes which are not essential to the normal life of the cell
but confer an advantage to the cell in certain situations
such as antibiotic-resistant plasmids,The chromosome in
archaebacteria,like that of the eubacteria,is a single,
circular DNA molecule not contained within a nucleus,but
the size of the DNA molecule is often smaller than that of ￡,
coli.
Genetic material
plasmid
Basic structure
Some bacteria contain structures associated with specialist
functions,Granular structures,called inclusion bodies,can
often be seen under the light microscope,These granules are
usually for storage and may be membrane bound（与膜结合）,such as poly-β-hydroxybutyrate (PHB) granules（聚 β
羟丁酸盐 ）,or found scattered in the cytoplasm,such as
polyphosphate granules多聚磷酸盐颗粒或称为异染粒 (also
called metachromatic granules),Lipid droplets can also be
seen in some bacteria,An interesting inclusion body,the gas
vacuole,is found in Cyanobacteria (blue-green algae) and
other photosynthetic bacteria that live in an aqueous
environment,This protein-surrounded vacuole provides
buoyancy,allowing the bacteria to float near the surface of
the water.
4.7 Inclusion bodies
PHB granules
polyphosphate granules（ metachromatic
granules ）多聚磷酸盐颗粒或称为异染粒
Lipid droplets
gas vacuole
Inclusion bodies
Basic structure
Cell wall
Although bacteria do not have organized intracellular
membranes,invaginations （内陷结构） of the plasma
membrane called mesosomes are often seen in electron
micrographs,There is some debate as to whether these
mesosomes really exist and are not just an artefact（假象）
of the fixation process for electron microscopy,Their
function is thought to be in cell division,possibly in laying
down new cell-wall material（促进新细胞壁的形成） or in
the replication of the chromosome and its subsequent
distribution to daughter cells,
4.8 mesosomes
Basic structure
Other,more specialist and complex,intracellular
membrane systems are found in photosynthetic bacteria,
such as Chloroflexus（绿屈挠菌属） (green non-sulfur
bacteria绿色非硫细菌 ) and Rhodopseudomonas (purple
bacterium),associated with the trapping of light energy,
4.9 intracellular membrane systems
内膜系统
Special structure
Finally,a number of bacteria including mainly the
Bacillus （芽孢杆菌属） and Clostridiwn genera （梭菌属） produce a special reproductive structure（它无繁殖功能，为抗逆性休眠体） called the endospore芽孢,This
can be seen in the light microscope using either specialist
spore stains such as mala chite green （孔雀绿） or by
phase-contrast microscopy,The spore has a number of
layers surrounding the bacterial genetic material making
it incredibly resistant to all kinds of environmental stress
such as heat,UV irradiation,chemical disinfectants and
drying,As a number of important pathogenic bacteria
are spore producers,sterilization measures must
therefore be designed to remove these hardy structures as
some can withstand boiling for several hours,
4.10 sporeSpecial structure
spore
Site
attribute
Bacteria genera having endospore
Structure
Observation
function
revision
Exosporium
（芽孢外壁）
Spore coat
Core wall(核心壁或芽孢壁 )
nucleoid
Cortex(皮层 )
ribosome
core
Diagram of an endospore
A number of features are found on the surface of the bacteria which
aid the survival of the cell in the environment.
Definition Thin hair-like proteinaceous appendages,several
micrometers long,called pili菌毛 (s,pilus) or fimbriae纤毛（伞毛）
(s,fimbria) are often seen projecting from the surface of the cell in
electron micrographs,
Roles
A These structures are normally associated with the adhesion of
bacteria to surfaces ;
B there is one particular type of pilus,the sex pilus,which is involved
in the transfer of genetic material from one bacterium to another,
4.11 Pili or
fimbriaeSpecial structure
Definition Motile bacteria have one or more flagella (s,flagellum)
which are slender纤细,rigid 坚韧 structures up to 20 um long,
Roles Rotation of the flagellum in relation to the cell allows the
movement of the bacterium(鞭毛的旋转与细菌的运动有关 ),Normally,
bacteria move in response to external stimuli; an example of this is
chemotaxis(趋化性 ) when bacteria move towards nutrients or away
from harmful substances as a result of chemical gradients (由于化学梯度的结果 )
flagellaSpecial structure
痢疾杆菌 Shigella sonnei - rod
prokaryote; causes shigellosis
(bacterial dysentery) (x 22,400)
霍乱弧菌 Vibrio cholerae - vibrio-shaped prokaryote that causes cholera (x 15,575)
伤寒杆菌 Salmonella - rod prokaryote ;
note the flagella,Causes salmonellosis
(food poisoning),(x 20,800)
E,coli
The surface of cells are often covered by layers of
polysaccharide or proteinaceous material known as capsules or
slime layers,depending on their density,If it is diffuse (散开的 )and
easily lost it is called a slime layer,The polysaccharide layers are
sometimes called the glycocalyx(糖萼 ),However,some bacteria
have proteinaceous capsules,These layers play a role in
protecting the cell from desiccation and toxic compounds and
also in the adhesion of bacteria to surfaces.
4.12 Capsule or
slime layerSpecial structure
These additional surfaces layers have a number of
functions;
they act as permeability barriers to the cell surface;
(对细菌表面起渗透屏障的作用 )
they protect the bacteria from phagocytosis;
they protect the cell from desiccation;
they aid in the attachment (adhesion) of bacteria to
surfaces.
Role of capsule or
slime
5,The Gram-positive bacteria v.s,the
Gram-negative bacteria
The eubacteria are frequently divided
into two groups on the basis of their
reaction to a stain devised by Christian
Gram in 1884,
The differential reaction to the
staining procedure is because of the
structure of the cell envelope in these
two groups of bacteria,
The Gram-positive bacteria have a single
membrane called the cytoplasmic (or plasma)
membrane,surrounded by a thick layer of
peptidoglycan (20-80 nm),
The Gram-negative bacteria have only a
thin layer of peptidoglycan (1-3 nm) but on
the outside of this there is a further outer
membrane which acts as an additional
barrier,
The procedure is as follows,Fixed cells are stained with a
dark stain such as crystal violet,followed by iodine which
complexes with the stain in the cell wall of the bacteria,
Alcohol is added,which washes the dark stain of crystal
violet-iodine out of cells that have thin cell walls but not
from those that have thick cell walls,Finally,a paler stain
such as carbol fuschin(石炭酸复红 ),called a counter-stain,is
added which stains the decolorized cells pink but is not
seen on the dark staining cells that retained the first stain,
The cells that retain the stain (with thick cell walls) are
called Gram-positive and appear dark purple under light
microscopy,The ones that lose the stain (with thin cell
walls and an outer membrane) are called Gram-negative
and stain pink or pale purple.
The procedure for the Gram stain
5.1 The procedure for the Gram stain
Smear fixing
crystal violet
初染
iodine
媒染
Alcohol
脱色
carbol
fuschin
复染
Crystal violet-iodine
staining washing
E,coli
5.2 Result of Gram-stain
The cells that retain the stain (with thick cell
walls) are called Gram-positive and appear dark
purple under light microscopy,
The ones that lose the stain (with thin cell walls
and an outer membrane) are called Gram-
negative and stain pink or pale purple.
G+
G-
6.reproduction and colony morphological features
Reproduction
Fission
binary fission
equal binary fission
unequal binary fission
trinary fission only pelodictyon(暗网菌属 )
multiple fission only bdellovibro（蛭弧菌）
Budding budding bacteria（芽生细菌）
大肠杆菌裂殖
Colony morphological features
Size
Shape
Texture(油脂状、膜状、粘、脆等 )
Color
transparency（ 透明、半透明、不透明等 ）
Surface situation（ 光滑、皱褶、颗粒状龟裂、同心圆状等）
Upheaval leval（ swell,bulge） 隆起程度（扩展、
台状、低凸状、乳头状）
Surface luster（闪光、不闪光、金属光泽等）
Factors that affects colony feature
Culture time
Colony density
Flagella
Capsule or slime（ glycocalyx 糖被）
Spore
个体形态与群体形态之间存在着明显的相关性：无鞭毛，不能运动的细菌通常都形成较小，较厚，边缘园整的半球状菌落；有鞭毛运动能力强的细菌一般形成大而平坦、
边缘多缺刻（甚至成树根状）、不规则型的菌落；有糖被的细菌，会长出大型、透明、
蛋清状的菌落；有芽孢的细菌往往长出外观粗糙、干燥、不透明的且表面多褶皱的菌落等。
Close corelation between
individual shape and
colony feature
The colony of immotile bacteria always is smaller,thicker,
semi-spherical with round and tidy edges,Otherwise,bacteria
with flagella forms large,flat,nicked or even tree root liked,
irregular colony,
The colony of bacteria with polysaccharide envelope(glycocalyx糖被 ) is always large,transparent and like egg white,
Bacteria having endospore can grow to coarse,dessicant,opaque
colony with draped surface.
Usage
Colony plays important roles in the
following aspects of biological
researches：
Isolation
Purification
Identification
Bacterium counting
Screening and breeding of
microorganism
Bacteria related to food
Acetobacter (醋酸杆菌属 )
Listeria（李斯特氏菌属）
Lactobacillus（乳杆菌属）
Leuconostoc（明串珠菌）
Bifidobacterium（双歧杆菌属）
Bacillus（芽孢杆菌属）
Clostridium（梭状芽孢杆菌）
Micrococcus（微球菌属）
Streptococcus（链球菌）
Staphylococcus（葡萄球菌）
bacteria related to food
Pseudomonas假单胞杆菌属
Achromobacter无色杆菌属
Aicaligenes（产碱杆菌属）
Flavobacterium（黄色杆菌属）
Escherichia and enterobacter（埃希氏杆菌属和肠细菌属）
Salmonella（沙门氏菌）
Proteus（变形杆菌）
Fermentation has been a major way of preserving
food for thousands of years,Fermentation is a
means by which microbial growth causes
chemical and/or textural changes which form a
product that can be stored for extended periods,
The fermentation process is also used to create
new food flavors and odors.（味道和风味）
Fermented foods
Yoghurt is produced by S,thermophilus and L,
bulgaricus,With these organisms growing in
concert（协同生长）,acid is produced by
Streptococcus,and aroma components are
formed by Lactobacillus,Freshly prepared
yoghurt contains 109 g-1 of bacteria,
Dairy products（ 1） —— yogurt
Cheese is another microbial fermentation product,All cheese results
from a lactic acid fermentation of milk,The process requires the growth
of a starter culture（发酵剂，起子） in milk which produces flavor
changes （味变） and acid production,resulting in coagulation of milk
solids and formation of a curd（乳凝块）,Renin（肾素）,an enzyme
from calf stomachs (which can also be produced by genetically
engineered microorganisms),is used to assist in curd formation,The
curd is heated and pressed to remove the watery part of the milk or whey
（乳清）,salted,and then ripened（加上盐，然后便成熟）,The cheese
curd（干酪） can be ripened with or without additional microorganisms,
Cheese curd inoculation is used in the manufacture of Roquefort and
blue cheese.（干酪加曲用来生产法国浓味羊奶干酪和蓝干酪）
Dairy products（ 2） —— cheese
A variety of meat products,especially sausage
（香肠）,can be fermented,country-cured hams
（乡下腌制的火腿）,summer sausage（夏季香肠）,
salami（意大利香肠） and izushi,Pediocqccus
cerevisiae（啤酒片球菌） and L,plan-tarum（植物乳杆菌） are most often involved in sausage
fermentations,Izushi is based on the fermentation
of fresh fish,rice and vegetables by Lactobacillus.
Meat and fish
Bacteria also play a significant role in food
spoilage (detrimental changes to the food),
Foods with easily utilizable carbohydrates,
proteins and fats are ideal environments for
spoilage by microorganisms,
Food spoilage
For examples:
Milk undergoes a series of steps which include
increased lactic acid production by S.lactis（乳链球菌）,growth of more acid-tolerant organisms and
finally protein digestion by bacteria that results in
the formation of a putrid odor（腐臭气味 ） and bitter
flavor,
In canned foods,spoilage is typically caused by
fermentative bacteria such as Clostridia （梭状芽孢杆菌） which alter the texture and taste of the food as a
result of protein degradation,The production of
CO2and H2S during spoilage causes cans to swell,
More importantly the presence of bacterial
pathogens in food presents a significant problem。
Bacterium Disease Foods involved
Food infections
Enteropathogenic ￡,coli (0157) ￡,coli enteritis Cheese,meats
Listeria monocytogenes Listeriosis Dairy products
Salmonella typhimurium Salmonellosis Meats,poultry,
S,enteritidis eggs,dairy products
Vibrio parahaemolyticus V,Parahaemolyticus Seafood
gastro-enteritis
Major diseases and poisonings associated with food
细菌肠道致病菌大肠杆菌单核细胞增生李斯特氏菌鼠伤寒沙门氏菌肠炎沙门氏菌副溶血弧菌疾病大肠杆菌肠炎李斯特菌病沙门氏菌病副融血性弧菌胃肠炎涉及的食物干酪，肉类乳制品肉类，家禽蛋，乳制品，海产品食物感染
Clostridium perfringens Perfringens food poisoning Meats and
产气荚膜梭状芽孢杆菌 产生荚膜食物中毒 poultry
C,BotulinumBotulism botulism Fish,meats and
肉毒梭状芽孢杆菌 肉毒中毒 canned foods
Bacillus cereus B,cereus food poisoning Meats,rice,
蜡状芽孢杆菌 蜡状芽孢杆菌食物中毒 cereals,potatoes
Food poisoning
（ caused by toxin release）
化脓性链球菌
Streptococcus
pyogenes - coccoid
prokaryote; causes
pharyngitis,sinusitis,
otitis media (middle ear
infection),food
poisoning,puerperal
fever (childbed fever),
skin and wound
infections (scarlet fever,
erysipelas,impetigo),
Group A strep,SEM
x56,000
Plastic kitchen cutting board
surface - rod bacteria in a smooth
matrix; filamentous bacteria ( 丝状菌 ) -smooth oval cells; fungal
hyphae ( 真菌菌丝 ) with textured
spores ( 结构孢子 ) (x 2,270)
Rod-Shaped Bacterium,E,coli
(SEM x22,245) E,coli (0157:H7) - a
rod prokaryote,Hemorrhagic type
粪链球菌 Streptococcus
faecalis - coccoid prokaryote;
a pathogen causing skin and
wound infections
Young cells are G_,elder bacteria are always G+,
sporeless,motile or immotile,aerobic,Bacteria of this
genus have strong oxidative ability to oxidize alcohol into
acetic acid,therefore beneficial to acetic acid industry and
detrimental to alcohol beverage,Usually can be found in
fermented foodstuff,decayed fruits and vegetables,sour
wine and juices,For instance:
A.aceti(纹膜醋酸杆菌 ) is responsible for the sour wine and
juices;
A,xyliuum(胶醋酸杆菌 ) and A,suboxydans(弱氧化醋酸杆菌 )
may forms goos(粘性物质 )and impair the production of
vinegar.
Acetobacter
(醋酸杆菌属 )
Immotile,G+ bacillus organized in chains,
can be easily found in milk and plant product
such as L.casei(干酪乳杆菌 ),L.bulgarics(保加利亚乳杆菌 ),L.acidophilus(嗜酸乳杆菌 ),
L.thermophilus(嗜热乳杆菌 ),they are always
used as ferment starter for the making of
following dairy product,yogurt,cheese and
lactic acid,
Lactobacillus
（乳杆菌属）
乳酸杆菌
Salmonella
(沙门氏菌 )
Short,G- peritrichate motile bacillus,don’t
produce pigments on medium,ferment
glucose and other monosaccharides,
produce both acid and CO2(there few
exceptions),but can’t utilize lactose.
It’s an important enteropathogenic bacteria
and cause the infectious diseases and food
spoilage.
沙氏杆菌
Staphylococcus
(葡萄球菌属 )
G+,usually produce contact enzyme,existed
in the nasal cavity and on the skin or other parts
of body,S,aureus don’t produce pigments or
contact enzyme either,causing abscess and
wound pyogenesis,can produce enterotoxin
thus causing food poisoning.
Escherichia
( 埃希氏菌属 )
Short peritrichate bacillus,G-,hard to discriminate it
with enterobacter(肠杆菌属 ) under light microscopy
and on the medium,Both of them belong to coliform
group(大肠菌群 ),citrate can’t be used as the only
carbon source.
The members mainly exist in the animal or human
intestines,distributed in water and soil,Animportant
saprobe(saprophytes腐生菌 ) in food,If a mount of E,
coli are found in food,this indicates that the food has
been contaminated by manure,So there is strict
stipulation of the number of E,coli for food such as
water,milk and unheated beverages.
肠杆菌
E。 coli
E。 coliE。 coli
Bacillus
(芽孢杆菌属 )
G+,aerobic spore-producing bacillus,widely
existed in the environment,especially in the
soil and air,bacillus anthrax (炭疽芽孢杆菌 )of this
genus is a devastating pathogen which cause
anthracnose （炭疽病）,Other bacteria of this
genus usually cause the food spoilage such
as bacillus subtulis(枯草芽孢杆菌 ) and Bac,
Mycoides(蕈状芽孢杆菌 ),
芽孢杆菌炭疽杆菌炭疽杆菌炭疽杆菌
Section C Actinomyces
Definition,A group of filamentous Gram positive
bacteria reproduced by the formation of spores.
(为一类主要呈丝状生长和以孢子繁殖的革兰氏阳性细菌 )
Distribution,widely existed in the dry,a little alkaline
soils rich in organic materials,Geosmin produced by
actinomyces endow the mud with specific smell.
(广泛分布在含水量较低、有机物较丰富和呈微碱性的土壤中。泥土所特有的泥腥味，主要由防线菌产生的土腥味素所引起。每克土壤中防线菌孢子数可达 107个 )
炭疽杆菌
G+ anaerobic or slightly aerobic,spore-producing
bacillus,among them pathogen of Bacillus
clostridium ( 肉毒梭状芽孢杆菌 )are extremely
poisonous,Cl,Thermosaccharolyticum (热解糖梭菌 )
is obligate thermophilus bacterium catalyzing
saccharides,therefore is responsible for the
deterioration of canned fruits or vegetables,
Cl.putrefaciens(腐化梭菌 ) usually cause the spoilage
of proteinaceous food.
Clostridium
(梭状芽孢杆菌属 )
N o n a m e,t x t
放线菌与人类的关系极其密切，绝大多数属有益菌，对人类健康的贡献尤为突出。至今已报道过的近万种抗生素中，约
70％由放线菌产生；近年来筛选到的许多新的生化药物多数是放线菌的次生代谢产物，包括抗癌剂、酶抑制剂、抗寄生虫剂、
免疫抑制剂和农用杀虫 (杀菌 )剂等。放线菌还是许多酶、维生素等的产生菌。 Frankia(弗兰克氏菌屑 )对非豆科植物的共生固氮具有重大的作用。此外，放线菌在甾体转化、石油脱蜡和污水处理中也有重要应用。由于许多放线菌有极强的分解纤维素、
石蜡、角蛋白、琼脂和橡胶等的能力，故它们在环境保护、提高土壤肥力和自然界物质循环中起着重大作用。只有极少数放线菌能引起人和动、植物病害。
1.morphology
Substrate mycelium
Aerial mycelium
Spore-bearing mycelium
放线菌
Aerial mycelium
twist Spore-bearing mycelium
conidium
Substrate mycelium
medium
annulus spore-
bearing mycelium
Streptomyces has the most typical
morphological features and is the most
closed to human life,
Diagram of streptomyces(链霉菌 )
Morphology of spore-bearing mycelium(streptomyces)
Nocardia 诺卡氏菌属 Micromonospora
Microbispora
Microtetraspora
Micropolyspora
Streptosporangium
Actinoplanes
pirillospora
The colony is constituted by mycelium,Slender hyphae of the
actinomyces grows slowly and interweaved,thus lead to the small,
wrinkled colony with tight texture and dry surface,The substrate
mycelium grows into the medium,so the colony tightly attached to it,
hence it’s hard to pick it up with innoculating loop,At the very
beginning of the formation of the colony,it’s similar with that of
bacterial,because the aerial mycelium has not differentiated into
spore-bearing mycelium yet,When a large amount of spores have
been produced and spreaded on the surface of colony,the typical
irradiative,fine powder -liked or granular colony was formed.
Colony features
分生孢子：最常见，如 streptomyces等大多数种类借孢子孢囊孢子基内菌丝断裂：如 Nocardianocardia (诺卡氏菌属 )
借菌丝任何菌丝片段：各种放线菌
reproduction
Actinomyces in food
Scarcely can actinomyces cause the spoilage
and deterioration of food,Only one genus might
endanger the safety of it——Streptomyces(链霉菌属 ),The members of this group contaminate
vegetables via soil,they also exist in man’s mouth,
Some species can cause the plant disease at room
temperature.
Section D Other prokaryotes
Cyanobacteria ever called blue algae or blue-green
algae is a group of large visible prokaryotes which is
Gram-negative,flagellaless,with chlorophyl while
without chloroplast,and can photosynthesize the
oxygen.
Cynobacteria has a long evolving history and
widely exists in the environment such as water
bodies of all kinds,soil,internal or external of some
living creatures,even on the rock surface or other
adverse environment can also find them,so they are
famed as ―pioneer organism”
绿藻蓝细菌
（
螺旋藻
）
蓝细菌
（
鱼腥草
）
旧名蓝藻（ blue algae）或蓝绿藻（ blue-green algae），是一类进化历史悠久,G阴性、无鞭毛、含叶绿素 a（但不形成叶绿体）、能进行产氧性光合作用的大型原核生物。蓝细菌广泛分布与自然界，包括各种水体、土壤中和部分生物体内外，甚至在岩石表面和其他恶劣环境中都可找到他们的踪迹，因此有,先锋生物,之美称。他的发展使整个地球大气从无氧状态发展到有氧状态,从而孕育了一切好氧生物的进化和发展,在人类生活中,蓝细菌有着重大的经济价值,有许多食用种类,目前已开发成有一定经济价值的螺旋藻产品,至今已知有 120多种蓝细菌具有固氮能力,特别是与满江红鱼腥蓝细菌共生的水生蕨类满江红,是一种良好的绿肥,some cynobacteria are responsible for the ―赤潮,of
sea water and ―水华,of lake.
Chlamydia is a group of G-,obligate energy parasite(专性能量寄生 ) prokaryotes,They have the following features:
1,Cell structure
2,Both have RNA and DNA
3,Have cell wall (but without peptidoglycan)
4,Have ribosome
5,Lack energy-producing system,obligate intracellular
parasite
6,Sensitive to antibiotics and medicine that inhibiting
bacteria
7,Reproduce by binary fission
8,Only can be cultured within living eukaryotic cell
Chlamydia (衣原体 )
Mycoplasma is the smallest prokaryote
without cell wall between independent living
and intracellular parasite,Many species are
pathogens of animal and human,
Mycoplasm
(支原体 )
Features of mycoplasma
The cell is so small that nearly can’t be seen
under the light microscopy.
The membrane is rigid than other
prokaryotes in that contains sterols.
Without cell wall therefore sensitive to
osmotic pressure and insensitive to the
antibiotics that inhibiting the synthesis of the
cell wall,so gram stain is negative and
without fixed shape.
(continued)
Colony is small and looks like oil fried
egg.
reproduce by binary fission and
budding.
Although fastidious,can grow on the
special mediums.
Most of them can utilize saccharide as
carbon source,aerobic or anearobic,
Small genome.
Named after H.T.Ricketts,an American doctor
who firstly discovered the pathogen for 落基山
ship fever(船热，斑疹伤寒 ),and lose life
because of infection by accidence,Rickettsia is
a group of obligate parasite G- prokaryotes.
The feature of it distinguished with cytoplasm
is that it has cell wall and can’t live
independently,distinguished with chlamydia,its
cell is larger and has energy-producing system,
Rickettsia
(立克次氏体 )
Rickettsia
