Chapter 4
Nutrition and medium of microbes
(微生物的营养和培养基 )
Nutrition,the most basic physiological function for
organisms to intake the energy and material that is necessary
for living and reproduction from the outside environment,
(营养 是指生物体从外部环境中摄取对其生命活动必需的能量和物质,以满足正常生长和繁殖需要的一种最基本的生理功能,)
Nutrient,it is referred to as the nutritional material including the
unconventional material form—— ray radiation in microbiology.
(营养物则是指具有营养功能的物质,在微生物学中,它还非常规物质形式的光辐射能在内,)
Nutriton and nutrient
Section A
six nutritional elements of microbes
(微生物的六类营养要素 )
The chemical composition of the microorganism cells and
their metabolite determines what nutrient they need.
As bacteria are a very disparate group of microbes that can exist in a wide
range of environments,and can be split into a number of different nutritional
groups with very different prerequisites for growth,the ingredients in the
medium will depend on the individual species,The common requirements
of all bacteria are water,a source of energy,carbon,nitrogen,essential
inorganic ions such as phosphate,sulfate,sodium,calcium,magnesium,
potassium and iron and a number of trace elements (Zn,Mn,Mo,Se,Co,Cu,
Ni,W),For heterotrophs,energy and carbon can be derived from the same
molecule.
The composition of the microbe cell
carbon,hydrogen,oxygen,nitrogen and essential inorganic ions
such as phosphate,sulfate,sodium,calcium,magnesium,potassium
and iron and a number of trace elements (Zn,Mn,Mo,Se,Co,Cu,Ni,
W)
,water,carbohydrates,protein,nucleic acid,lipoid,vitamine,
antibiotic,inorganic ion.
Elemental level
Compound level
1.Carbon source
2.Nitrogen source
3.Energy source
4.Growth factor
5.Mineral salts
6.Water
Level of Nutritional
elements
What does a microbe need for
growth?
Carbon source are defined as all the nutrients that can satisfy
the need for carbon during the process of microbial growth,It
is also called macronutrients(大量营养物 ) in that it is in the
most greatest need only secondary to water,The spectrum of
carbon sources (碳源谱 )are extremely wide.
The spectrum of carbon sources can be divided into two types,
organic carbon and inorganic carbon,
Those who have to depend on the organic carbon source are
heterotrophs,the majority of microorganisms are of this type.
And those who use inorganic carbon source as main form are
autotrophs,Only a few of microbes are of this type.
Carbon source
Heterotrophs and autotrophs
For all the heterotrophs,the carbon source is also energy
source at the same time,therefore this kind of carbon resources
is called difunctional nutrient(双功能营养物 ).
Nitrogen source provide the microorganism with the element
of nitrogen for its living and reproduction,
The spectrum of nitrogen source is also quite wide and have
two types,organic nitrogen and inorganic nitrogen.
In the culture medium the commonly used organic nitrogen
are beef extract,yeast extract and peptone(牛肉膏,酵母膏和蛋白胨 ).
Nitrogen source
Amino acid autotrophs(氨基酸自养型生物 ) is a group of
organism who don’t need amino acid as their nitrogen
source and can self-synthesize all the amino acids they
need using simple nitrogen source as material.
Otherwise,amino acid heterotrophs (氨基酸异养型生物 ) intake
ready amino acids as their nitrogen resources,All the animals
and a number of heterotrophs are amino acids
heterotrophs.
Amino acid autotrophs and
amino acid heterotrophs
Energy source are those nutrients that provide the initial
energy or ray radiation energy for its living,
The spectrum of energy source can be divided into two
types,chemical material(organic or inorganic) and irradiation
energy,Chemotrophs use chemical materials and
phototrophs use irradiation energy.
Energy source
Monofunctional nutrient)—— ray irradiation energy
（ 单功能营养物 energy source）
Bifunctional nutrient)—— deoxidized（还原态 的） inorganic NH4
(双功能营养物 （ energy source and nitrogen source）
Trifunctional nutrient)—— amino acids
(三功能营养物 source of carbon,nitrogen and energy）
A certain nutrient might has two or three nutritional
functions,that is,it can be used as the source of
carbon,nitrogen or energy,while some only have
one function,
Growth factor
Growth factor is a kind of organic material can’t be self -
synthesized by auxotrophs(营养缺陷型微生物 ) with simple
carbon source and nitrogen source,while is necessary for
microorganisms to regulate the normal metabolism.
Although growth factor is an important nutrient element,it is
different from the carbon source,energy source and nitrogen
source in that not any certain organism need the growth factor
provided by the environment.
Bacteria that can synthesize all they require from these
basic ingredients are called prototrophs（ 原养型微生物 ）
and most microorganisms that survive in the outside
environment can do this.
Prototrophs
Microbes that have become adapted to life in a situation
rich with nutrients such as the human body may require
other growth factors to be provided,such as vitamins,
amino acids or nitrogenous bases,These organisms are
called auxotrophs（ 营养缺陷型 ）,
Leuconostoc mesenterdides,for example,requires over 40
additional growth factors,Bacterial growth media are
therefore designed to suit the organism of interest and may
be either defined or complex media.
auxotrophs
Microbes can be divided into three types on the basis of situation of
the need for growth factor:
Auxoheterotrophs(生长因子异养性微生物 )
Auxoautotrophs (生长因子自养性微生物 )
Growth factor over synthesized microbes(生长因子过量合成的微生物 )
Normally,lactic bacteria needs vitamines as growth factor,
many microbes and their auxotroph mutant strains need
nitrogenous base.
Some natural material contains rich growth factors therefore
can act as growth factor source such as yeast extract,
cornsteep liquor(玉米浆 ),liver infusion(肝浸液 ),malt extract (麦芽汁 ) etal.
Some microbes has the ability of secrete certain vitamines
etal,in large amount during the metabolism,thus can be
used as vitamine-producing bacterial strains.
Mineral salts
Mineral salts or inorganic salts(无机盐或矿质元素 ) supply
the important elements except the carbon source and
nitrogen source.
macroelements大量元素 10-3~10-4 mol/L
Mineral salts
microelements微量元素 10-6~10-8 mol/L
As far as the macroelement is concerned,when a medium is
prepared,above all we usually select K2HPO4 and MgSO4,for
they can provide four elements that the microbes need in the
greatest amount at the same time,Normally enough trace
elements are present in the water.
Section B
Nutritional type of microbe
Photoautotrophs (光能自养微生物 )
Photoheterotrophs (光能异养微生物 )
Chemoautotrophs (化能自养微生物 )
Chemoheterotrophs (化能异养微生物 )
saprophytism(腐生 )—— dead（ saprophyte）
Chemoheterotrophs
parasitism (寄生 ) —— living（ parasite）寄生 菌
Obligatory parasitism
Parasitism Facultative parasitism
Facultative saprophytism
Section C
How the nutrients enter into the cell
（营养物质进入细胞的方式）
Don‘t through the carrier protein of membrane,Simple diffusion
Styles don’t consunme energy,facilitated diffusion
pass through the
carrier protein active transport（ untouched）
consume energy
group translocati（ changed）
Simple diffusion
out of the
membrane
membrane cytoplasm
Conformation
changes
conformation
comeback
Facilitated diffusion
Active transport
Conformation changes
by consuming energy
Come back to the
original conformation
Enzyme A
Enzyme B
Group translocation
classification criterium Nutritional types
1,energy sources
2,H donator
3,Carbon sources
4,amino-synthesis ability
5,Growth factor
6,Ways of intaking
7,Living or dead organics
Section D
Medium（培养基）
Medium is an artificial mixture containing all
the six appropriated essential nutritional
elements (requirements ) for the growth and
reproduction or the production of metabolites of
a certain microbe,
(培养基是指由人工配制的 \适合微生物生长繁殖或产生代谢产物用的混合营养料,任何培养基都具备微生物生长所需要的六大营养要素且期间的比例是合适的 )
1.Principles and methods for the medium
selection and designing
(1) Four principles
A,Definite aim 目的明确
B,Harmony (appropriate) nutrient 营养协调
C,proper physical and chemical condition 理化适宜
pH,osmotic pressure,redox potential (氧化还原电势 )
D,economical 经济节约
1.Principles and methods for the medium
selection and designing
Four methods
A ecology simulation 生态模拟
B literature referring 参阅文献
C self-designing 精心设计
D comparative trying 实验比较
2,Medium classification
2.1 On the basis of the knowledge of its ingredients:
(按对培养基成分的了解分类 )
A complex media (undefined media)
B synthetic media (chemical defined media)
C semi-synthetic media (semi-defined media )
2,Medium classification
2.2 On the basis of physiological condition
(按培养基外观的物理状态分类 )
A liquid media
B solid media
C semi-solid media
D dehydrated culture media (dehydrated commercial media
or pre-fabricated dried culture media)
脱水商品培养基或预制干燥培养基
solid media,
solidified media (gelling agent,1~2%agar,gelatin,alginate)
irreversible solidified media (silica gel as gelling agent
or serum media )
natural solid media
Membrane filter (滤膜 )
2,Medium classification
2.3 On the basis of the function,
(按培养基对微生物的功能分类 )
A selected media (选择培养基 )
enriched selected media (加富性选择培养基 )
inhibited selected media (抑制性选择培养基 )
B differential media (鉴别培养基 )
eg,Eosin Methylene Blue (EMB)
Microbes are grown (cultured) in the laboratory in either
liquid or solid medium,Bacterial growth media should
contain all the essential requirements for growth,an energy,
carbon and nitrogen source as well as the essential ions,
phosphate,sulfate,sodium,calcium,magnesium,potassium
and iron,and various trace elements,Prototrophs require no
additional ingredients in the medium,while auxotrophs
require additional growth factors such as amino acids,
vitamins and nitrogenous bases,The media used may be
denfined (synthetic) media(限定，合成培养基 ) where all the
ingredients are known or complex media（天然培养基）
containing a mixture of undefined nutrients,Agar is used to
solidify a liquid medium,Selective or differential media are
used to detect the presence of particular groups of microbes.
Key Notes—— growth media
Each bacterial species has an optimum
temperature,oxygen concentration,pH and
water activity for growth and will survive in
a range of conditions around these optima.
Key Notes——
Environmental conditions for growth
in the laboratory bacteria are normally grown (cultured) in
either liquid medium,in flasks,bottles or large culture vessels
called fermenters,or solid medium,in Petri dishes,which are
round,normally plastic,sterile dishes,Introduction of
microbes into or on to these media is called inoculation,
The nature of the medium depends on the microorganism's
natural environment and on the reason why it is being grown,
Normally,to isolate large numbers of microbes or their
products,liquid culture is used but solid medium is used for
the isolation of individual bacteria and for storage,
Liquid medium and solid medium
Liquid medium (or broth) can be converted into solid
medium by the addition of agar (1-2%) which is isolated
from seaweed,It is a particularly useful polysaccharide
polymer because,once it is melted by boiling,it does not
harden until it is cooled to 40-42° C which allows the
addition of temperature-sensitive ingredients,such as
proteins,before it sets,Having set,it will not melt again
until it has been heated to 80-90° C.Agar is also not
normally degraded by bacteria,Petri dishes containing a
nutrient agar are often referred to as agar plates.
How broth becomes solid media？
agar
A defined（限定） or synthetic medium contains known
ingredients which are usually the basic requirements for growth of
a particular microbe,These are normally simple (minimal) media
that contain the minimal requirements for growth,Examples of
defined media for the photosynthetic Cyanobacteria (note the lack
of a carbon source) and heterotrophic E,coli are shown in Table,
Defined medium
A complex medium contains undefined ingredients such
as proteolytic digests of meat (peptones) and meat and yeast
extracts which provide enough ingredients (amino acids,
vitamins,sugars and bases) to sustain the growth of a wide
range of microbes,Complex media such as nutrient broth
(NB) and tryptic soya broth (TSB豆胨肉汤 ) are routinely used
for cultivation of bacteria in the laboratory and are
particularly useful for growing bacteria whose growth
requirements have not been defined,Blood is frequently
used as an additive to media,for the isolation of human
pathogens,as it provides many of the essential nutrients for
the growth of fastidious human pathogens such as
Streptococcus.
Complex medium
1,Peptones
2,meat and yeast extracts
3,nutrient broth (NB)
4,tryptic soya broth (TSB）
5,blood
The following substances are normally
added to the complex media：
Summarization
Specialist selective and differential media are
frequently used to isolate particular groups of
microbes especially in hospital laboratories,
These are media designed to select for a
particular group of microbes or to differentiate
between two species,They therefore contain
ingredients which suppress the growth of
unwanted bacteria,encourage the growth of those
of interest and,in the case of differential media,
some means of distinguishing between two
different types of microbe,
Selective and differential
media
A medium containing only acetate as a carbon source would
be selective for organisms that grow on acetate,Blood in agar
will allow the detection of those bacteria capable of lysing red
blood cells such as β-hemolytic streptococci,seen as zones of
clearing (hemolysis),MacConkey agar is one of many selective
media for E,coli from environmental or medical samples,It
contains bile salts and dyes that suppress the growth of Gram-
positive bacteria but allows Gram-negative organisms to grow,It
is also a differential medium in that it allows the distinction
between lactose-fermenting organisms (e.g,￡,coli) and other
non-fermenters (e.g,Shigella sp),Lactose in the medium is
fermented by E,coli producing acid which causes an indicator
dye to change color to red,Colonies that ferment lactose are
therefore red whereas non-fermenters are white.
Examples
Nutrition and medium of microbes
(微生物的营养和培养基 )
Nutrition,the most basic physiological function for
organisms to intake the energy and material that is necessary
for living and reproduction from the outside environment,
(营养 是指生物体从外部环境中摄取对其生命活动必需的能量和物质,以满足正常生长和繁殖需要的一种最基本的生理功能,)
Nutrient,it is referred to as the nutritional material including the
unconventional material form—— ray radiation in microbiology.
(营养物则是指具有营养功能的物质,在微生物学中,它还非常规物质形式的光辐射能在内,)
Nutriton and nutrient
Section A
six nutritional elements of microbes
(微生物的六类营养要素 )
The chemical composition of the microorganism cells and
their metabolite determines what nutrient they need.
As bacteria are a very disparate group of microbes that can exist in a wide
range of environments,and can be split into a number of different nutritional
groups with very different prerequisites for growth,the ingredients in the
medium will depend on the individual species,The common requirements
of all bacteria are water,a source of energy,carbon,nitrogen,essential
inorganic ions such as phosphate,sulfate,sodium,calcium,magnesium,
potassium and iron and a number of trace elements (Zn,Mn,Mo,Se,Co,Cu,
Ni,W),For heterotrophs,energy and carbon can be derived from the same
molecule.
The composition of the microbe cell
carbon,hydrogen,oxygen,nitrogen and essential inorganic ions
such as phosphate,sulfate,sodium,calcium,magnesium,potassium
and iron and a number of trace elements (Zn,Mn,Mo,Se,Co,Cu,Ni,
W)
,water,carbohydrates,protein,nucleic acid,lipoid,vitamine,
antibiotic,inorganic ion.
Elemental level
Compound level
1.Carbon source
2.Nitrogen source
3.Energy source
4.Growth factor
5.Mineral salts
6.Water
Level of Nutritional
elements
What does a microbe need for
growth?
Carbon source are defined as all the nutrients that can satisfy
the need for carbon during the process of microbial growth,It
is also called macronutrients(大量营养物 ) in that it is in the
most greatest need only secondary to water,The spectrum of
carbon sources (碳源谱 )are extremely wide.
The spectrum of carbon sources can be divided into two types,
organic carbon and inorganic carbon,
Those who have to depend on the organic carbon source are
heterotrophs,the majority of microorganisms are of this type.
And those who use inorganic carbon source as main form are
autotrophs,Only a few of microbes are of this type.
Carbon source
Heterotrophs and autotrophs
For all the heterotrophs,the carbon source is also energy
source at the same time,therefore this kind of carbon resources
is called difunctional nutrient(双功能营养物 ).
Nitrogen source provide the microorganism with the element
of nitrogen for its living and reproduction,
The spectrum of nitrogen source is also quite wide and have
two types,organic nitrogen and inorganic nitrogen.
In the culture medium the commonly used organic nitrogen
are beef extract,yeast extract and peptone(牛肉膏,酵母膏和蛋白胨 ).
Nitrogen source
Amino acid autotrophs(氨基酸自养型生物 ) is a group of
organism who don’t need amino acid as their nitrogen
source and can self-synthesize all the amino acids they
need using simple nitrogen source as material.
Otherwise,amino acid heterotrophs (氨基酸异养型生物 ) intake
ready amino acids as their nitrogen resources,All the animals
and a number of heterotrophs are amino acids
heterotrophs.
Amino acid autotrophs and
amino acid heterotrophs
Energy source are those nutrients that provide the initial
energy or ray radiation energy for its living,
The spectrum of energy source can be divided into two
types,chemical material(organic or inorganic) and irradiation
energy,Chemotrophs use chemical materials and
phototrophs use irradiation energy.
Energy source
Monofunctional nutrient)—— ray irradiation energy
（ 单功能营养物 energy source）
Bifunctional nutrient)—— deoxidized（还原态 的） inorganic NH4
(双功能营养物 （ energy source and nitrogen source）
Trifunctional nutrient)—— amino acids
(三功能营养物 source of carbon,nitrogen and energy）
A certain nutrient might has two or three nutritional
functions,that is,it can be used as the source of
carbon,nitrogen or energy,while some only have
one function,
Growth factor
Growth factor is a kind of organic material can’t be self -
synthesized by auxotrophs(营养缺陷型微生物 ) with simple
carbon source and nitrogen source,while is necessary for
microorganisms to regulate the normal metabolism.
Although growth factor is an important nutrient element,it is
different from the carbon source,energy source and nitrogen
source in that not any certain organism need the growth factor
provided by the environment.
Bacteria that can synthesize all they require from these
basic ingredients are called prototrophs（ 原养型微生物 ）
and most microorganisms that survive in the outside
environment can do this.
Prototrophs
Microbes that have become adapted to life in a situation
rich with nutrients such as the human body may require
other growth factors to be provided,such as vitamins,
amino acids or nitrogenous bases,These organisms are
called auxotrophs（ 营养缺陷型 ）,
Leuconostoc mesenterdides,for example,requires over 40
additional growth factors,Bacterial growth media are
therefore designed to suit the organism of interest and may
be either defined or complex media.
auxotrophs
Microbes can be divided into three types on the basis of situation of
the need for growth factor:
Auxoheterotrophs(生长因子异养性微生物 )
Auxoautotrophs (生长因子自养性微生物 )
Growth factor over synthesized microbes(生长因子过量合成的微生物 )
Normally,lactic bacteria needs vitamines as growth factor,
many microbes and their auxotroph mutant strains need
nitrogenous base.
Some natural material contains rich growth factors therefore
can act as growth factor source such as yeast extract,
cornsteep liquor(玉米浆 ),liver infusion(肝浸液 ),malt extract (麦芽汁 ) etal.
Some microbes has the ability of secrete certain vitamines
etal,in large amount during the metabolism,thus can be
used as vitamine-producing bacterial strains.
Mineral salts
Mineral salts or inorganic salts(无机盐或矿质元素 ) supply
the important elements except the carbon source and
nitrogen source.
macroelements大量元素 10-3~10-4 mol/L
Mineral salts
microelements微量元素 10-6~10-8 mol/L
As far as the macroelement is concerned,when a medium is
prepared,above all we usually select K2HPO4 and MgSO4,for
they can provide four elements that the microbes need in the
greatest amount at the same time,Normally enough trace
elements are present in the water.
Section B
Nutritional type of microbe
Photoautotrophs (光能自养微生物 )
Photoheterotrophs (光能异养微生物 )
Chemoautotrophs (化能自养微生物 )
Chemoheterotrophs (化能异养微生物 )
saprophytism(腐生 )—— dead（ saprophyte）
Chemoheterotrophs
parasitism (寄生 ) —— living（ parasite）寄生 菌
Obligatory parasitism
Parasitism Facultative parasitism
Facultative saprophytism
Section C
How the nutrients enter into the cell
（营养物质进入细胞的方式）
Don‘t through the carrier protein of membrane,Simple diffusion
Styles don’t consunme energy,facilitated diffusion
pass through the
carrier protein active transport（ untouched）
consume energy
group translocati（ changed）
Simple diffusion
out of the
membrane
membrane cytoplasm
Conformation
changes
conformation
comeback
Facilitated diffusion
Active transport
Conformation changes
by consuming energy
Come back to the
original conformation
Enzyme A
Enzyme B
Group translocation
classification criterium Nutritional types
1,energy sources
2,H donator
3,Carbon sources
4,amino-synthesis ability
5,Growth factor
6,Ways of intaking
7,Living or dead organics
Section D
Medium（培养基）
Medium is an artificial mixture containing all
the six appropriated essential nutritional
elements (requirements ) for the growth and
reproduction or the production of metabolites of
a certain microbe,
(培养基是指由人工配制的 \适合微生物生长繁殖或产生代谢产物用的混合营养料,任何培养基都具备微生物生长所需要的六大营养要素且期间的比例是合适的 )
1.Principles and methods for the medium
selection and designing
(1) Four principles
A,Definite aim 目的明确
B,Harmony (appropriate) nutrient 营养协调
C,proper physical and chemical condition 理化适宜
pH,osmotic pressure,redox potential (氧化还原电势 )
D,economical 经济节约
1.Principles and methods for the medium
selection and designing
Four methods
A ecology simulation 生态模拟
B literature referring 参阅文献
C self-designing 精心设计
D comparative trying 实验比较
2,Medium classification
2.1 On the basis of the knowledge of its ingredients:
(按对培养基成分的了解分类 )
A complex media (undefined media)
B synthetic media (chemical defined media)
C semi-synthetic media (semi-defined media )
2,Medium classification
2.2 On the basis of physiological condition
(按培养基外观的物理状态分类 )
A liquid media
B solid media
C semi-solid media
D dehydrated culture media (dehydrated commercial media
or pre-fabricated dried culture media)
脱水商品培养基或预制干燥培养基
solid media,
solidified media (gelling agent,1~2%agar,gelatin,alginate)
irreversible solidified media (silica gel as gelling agent
or serum media )
natural solid media
Membrane filter (滤膜 )
2,Medium classification
2.3 On the basis of the function,
(按培养基对微生物的功能分类 )
A selected media (选择培养基 )
enriched selected media (加富性选择培养基 )
inhibited selected media (抑制性选择培养基 )
B differential media (鉴别培养基 )
eg,Eosin Methylene Blue (EMB)
Microbes are grown (cultured) in the laboratory in either
liquid or solid medium,Bacterial growth media should
contain all the essential requirements for growth,an energy,
carbon and nitrogen source as well as the essential ions,
phosphate,sulfate,sodium,calcium,magnesium,potassium
and iron,and various trace elements,Prototrophs require no
additional ingredients in the medium,while auxotrophs
require additional growth factors such as amino acids,
vitamins and nitrogenous bases,The media used may be
denfined (synthetic) media(限定，合成培养基 ) where all the
ingredients are known or complex media（天然培养基）
containing a mixture of undefined nutrients,Agar is used to
solidify a liquid medium,Selective or differential media are
used to detect the presence of particular groups of microbes.
Key Notes—— growth media
Each bacterial species has an optimum
temperature,oxygen concentration,pH and
water activity for growth and will survive in
a range of conditions around these optima.
Key Notes——
Environmental conditions for growth
in the laboratory bacteria are normally grown (cultured) in
either liquid medium,in flasks,bottles or large culture vessels
called fermenters,or solid medium,in Petri dishes,which are
round,normally plastic,sterile dishes,Introduction of
microbes into or on to these media is called inoculation,
The nature of the medium depends on the microorganism's
natural environment and on the reason why it is being grown,
Normally,to isolate large numbers of microbes or their
products,liquid culture is used but solid medium is used for
the isolation of individual bacteria and for storage,
Liquid medium and solid medium
Liquid medium (or broth) can be converted into solid
medium by the addition of agar (1-2%) which is isolated
from seaweed,It is a particularly useful polysaccharide
polymer because,once it is melted by boiling,it does not
harden until it is cooled to 40-42° C which allows the
addition of temperature-sensitive ingredients,such as
proteins,before it sets,Having set,it will not melt again
until it has been heated to 80-90° C.Agar is also not
normally degraded by bacteria,Petri dishes containing a
nutrient agar are often referred to as agar plates.
How broth becomes solid media？
agar
A defined（限定） or synthetic medium contains known
ingredients which are usually the basic requirements for growth of
a particular microbe,These are normally simple (minimal) media
that contain the minimal requirements for growth,Examples of
defined media for the photosynthetic Cyanobacteria (note the lack
of a carbon source) and heterotrophic E,coli are shown in Table,
Defined medium
A complex medium contains undefined ingredients such
as proteolytic digests of meat (peptones) and meat and yeast
extracts which provide enough ingredients (amino acids,
vitamins,sugars and bases) to sustain the growth of a wide
range of microbes,Complex media such as nutrient broth
(NB) and tryptic soya broth (TSB豆胨肉汤 ) are routinely used
for cultivation of bacteria in the laboratory and are
particularly useful for growing bacteria whose growth
requirements have not been defined,Blood is frequently
used as an additive to media,for the isolation of human
pathogens,as it provides many of the essential nutrients for
the growth of fastidious human pathogens such as
Streptococcus.
Complex medium
1,Peptones
2,meat and yeast extracts
3,nutrient broth (NB)
4,tryptic soya broth (TSB）
5,blood
The following substances are normally
added to the complex media：
Summarization
Specialist selective and differential media are
frequently used to isolate particular groups of
microbes especially in hospital laboratories,
These are media designed to select for a
particular group of microbes or to differentiate
between two species,They therefore contain
ingredients which suppress the growth of
unwanted bacteria,encourage the growth of those
of interest and,in the case of differential media,
some means of distinguishing between two
different types of microbe,
Selective and differential
media
A medium containing only acetate as a carbon source would
be selective for organisms that grow on acetate,Blood in agar
will allow the detection of those bacteria capable of lysing red
blood cells such as β-hemolytic streptococci,seen as zones of
clearing (hemolysis),MacConkey agar is one of many selective
media for E,coli from environmental or medical samples,It
contains bile salts and dyes that suppress the growth of Gram-
positive bacteria but allows Gram-negative organisms to grow,It
is also a differential medium in that it allows the distinction
between lactose-fermenting organisms (e.g,￡,coli) and other
non-fermenters (e.g,Shigella sp),Lactose in the medium is
fermented by E,coli producing acid which causes an indicator
dye to change color to red,Colonies that ferment lactose are
therefore red whereas non-fermenters are white.
Examples
