Bacterial Morphology and Structure
Xiao-Kui Guo PhD
http://basic.shsmu.edu.cn/passw/micro2/index.asp
SIZE OF BACTERIA
? Unit for measurement,
Micron or micrometer,μm,
1μm=10-3mm
? Size,
Varies with kinds of bacteria,and
also related to their age and external
environment,
? Cocci,sphere,1μm
? Bacilli,rods,0.5-1 μm in width -3 μm in length
? Spiral bacteria,1~3 μm in length and 0.3-0.6 μm in width
Structure of Bacteria
Particular structures
capsule 荚膜
flagella 鞭毛
pili 菌毛
spore 芽胞
Essential structures
cell wall 细胞壁
cell membrane 细胞膜
Cytoplasm 细胞质
nuclear material 核质
Gram +
Gram -
Cell wall
Cell (inner) membrane Outer membrane
Ribosomes
Granule
Cell wall
Nucleoid Cell membrane
Capsule
Flagellum
Pili
Gram,C,1884,Ueber die isolirte Farbung
der Schizomyceten in Schnitt?und
Trockenpraparaten,Fortschritte der
Medicin,Vol,2,pages 185-189,
1884,Christian Gram,First publication for the Gram stain method)
Editor's note,I would like to testify that I have found the Gram method to be one of
the best and for many cases the best method which I have ever used for staining
Schizomycetes,
Cell wall
? Situation,
outmost portion,
15-30nm in
thickness,10%-
25% of dry
weight,
Cell wall,Common peptidoglycan layer
? A backbone of N-acetyl glucosamine and N-acetylmuramic acid,Both discovered
in Gram positive and Gram negative bacteria,
? A set of identical tetrapeptide side chain attached to N-acetyl-muramic acid,
different components and binding modes in Gram positive and Gram negative
bacteria,
? A set of identical peptide cross bridges,only in Gram positive bacteria
Special components of
Gram positive cell wall
Teichoic acid
SPA / M POTEIN
Special components of
Gram negative cell wall
Functions of Cell Wall
? Maintaining the cell's characteristic shape- the rigid
wall compensates for the flexibility of the
phospholipid membrane and keeps the cell from
assuming a spherical shape
? Countering the effects of osmotic pressure
? Providing attachment sites for bacteriophages
? Providing a rigid platform for surface appendages-
flagella,fimbriae,and pili all emanate from the
wall and extend beyond it
? Play an essential role in cell division
? Be the sites of major antigenic determinants of
the cell surface。
? Resistance of Antibiotics
Wall-less forms of Bacteria,
? When bacteria are treated with 1) enzymes that are lytic for
the cell wall e.g,lysozyme or 2) antibiotics that interfere
with biosynthesis of peptidoglycan,wall-less bacteria are
often produced,
? Usually these treatments generate non-viable organisms,
Wall-less bacteria that can not replicate are referred to as
spheroplasts (when an outer membrane is present) or
protoplasts (if an outer membrane is not present),
? Occasionally wall-less bacteria that can replicate are
generated by these treatments (L forms),
Cell
membrane
? Site of biosynthesis of DNA,cell wall polymers and membrane lipids,Selective
permeability and transport of solutes into cells
? Electron transport and oxidative phosphorylation
? Excretion of hydrolytic exoenzymes
Mesosomes
? Mesosomes are specialized structures
formed by convoluted inveigh-nations of
cytoplasmic membrane,and divided into
septal and lateral mesosome,
Cytoplasm
? Composed largely of water,together with proteins,nucleic
acid,lipids and small amount of sugars and salts
? Ribosomes,numerous,15-20nm in diameter with 70S;
distributed throughout the cytoplasm; sensitive to
streptomycin and erythromycin site of protein synthesis
? Plasmids,extrachromosomal
genetic elements
? Inclusions,sources of stored
energy,e,g volutin
Plasmid Plasmids are small,circular/line，
extrachromosomal,double-stranded DNA
molecules。 They are capable of self-
replication and contain genes that confer
some properties,such as antibiotic
resistance,virulence factors。 Plasmids are
not essential for cellular survival,
Inclusions of
Bacteria
? Inclusions are
aggregates of various
compounds that are
normally involved in
storing energy
reserves or building
blocks for the cell,
Inclusions accumilate
when a cell is grown
in the presence of
excess nutrients and
they are often
observed under
laboratory conditions,
granulose
Nucleus
? Lacking nuclear
membrane,absence
of nucleoli,hence
known as nucleic
material or nucleoid,
one to several per
bacterium,
Capsules and slime layers
? These are structures surrounding the outside of the cell envelope,They
usually consist of polysaccharide; however,in certain bacilli they are
composed of a polypeptide (polyglutamic acid),They are not essential
to cell viability and some strains within a species will produce a capsule,
whilst others do not,Capsules are often lost during in vitro culture,
? Attachment
? Protection from phagocytic
engulfment,
? Resistance to drying,
? Depot for waste products,
? Reservoir for certain
nutrients,
? protection
Flagella
Monotrichate/Amphitrichate/Lophotrichate/Peritrichate
? Identification
of Bacteria
? Pathogenesis
? Motility of
bacteria
?Some bacterial species are mobile and possess
locomotory organelles - flagella,Flagella consist of a
number of proteins including flagellin
?The diameter of a flagellum is thin,20 nm,and
long with some having a length 10 times the
diameter of cell,Due to their small diameter,flagella
cannot be seen in the light microscope unless a
special stain is applied,Bacteria can have one or
more flagella arranged in clumps or spread all over
the cell,
Pili
? Pili are hair-like projections of the cell,They are
known to be receptors for certain bacterial viruses,
Chemical nature is pilin
? Classification and Function
a,Common pili or fimbriae,fine,rigid numerous,
related to bacterial adhesion
b,Sex pili,longer and coarser,only 1-4,related to
bacterial conjugation
Endospores
(spores)
? Dormant cell
? Resistant to adverse
conditions
- high temperatures
- organic solvents
? Produced when starved
? Contain calcium dipicolinate
DPA,Dipicolinic acid
? Bacillus and Clostridium
? Identification of
Bacteria
? Pathogenesis
? Resistance
Microscope
? Light Microscope
? Electron Microscope
? Darkfield Microscope
? Phase Contrast Microscope
? Fluorescence Microscope
? Cofocal Microscope）
Methods
Staining Methods
? Simple staining;
? Differential staining ( Gram
stain,Acid-fast stain),
? Special staining( Negative stain,
Spore stain,Flagella stain)
Xiao-Kui Guo PhD
http://basic.shsmu.edu.cn/passw/micro2/index.asp
SIZE OF BACTERIA
? Unit for measurement,
Micron or micrometer,μm,
1μm=10-3mm
? Size,
Varies with kinds of bacteria,and
also related to their age and external
environment,
? Cocci,sphere,1μm
? Bacilli,rods,0.5-1 μm in width -3 μm in length
? Spiral bacteria,1~3 μm in length and 0.3-0.6 μm in width
Structure of Bacteria
Particular structures
capsule 荚膜
flagella 鞭毛
pili 菌毛
spore 芽胞
Essential structures
cell wall 细胞壁
cell membrane 细胞膜
Cytoplasm 细胞质
nuclear material 核质
Gram +
Gram -
Cell wall
Cell (inner) membrane Outer membrane
Ribosomes
Granule
Cell wall
Nucleoid Cell membrane
Capsule
Flagellum
Pili
Gram,C,1884,Ueber die isolirte Farbung
der Schizomyceten in Schnitt?und
Trockenpraparaten,Fortschritte der
Medicin,Vol,2,pages 185-189,
1884,Christian Gram,First publication for the Gram stain method)
Editor's note,I would like to testify that I have found the Gram method to be one of
the best and for many cases the best method which I have ever used for staining
Schizomycetes,
Cell wall
? Situation,
outmost portion,
15-30nm in
thickness,10%-
25% of dry
weight,
Cell wall,Common peptidoglycan layer
? A backbone of N-acetyl glucosamine and N-acetylmuramic acid,Both discovered
in Gram positive and Gram negative bacteria,
? A set of identical tetrapeptide side chain attached to N-acetyl-muramic acid,
different components and binding modes in Gram positive and Gram negative
bacteria,
? A set of identical peptide cross bridges,only in Gram positive bacteria
Special components of
Gram positive cell wall
Teichoic acid
SPA / M POTEIN
Special components of
Gram negative cell wall
Functions of Cell Wall
? Maintaining the cell's characteristic shape- the rigid
wall compensates for the flexibility of the
phospholipid membrane and keeps the cell from
assuming a spherical shape
? Countering the effects of osmotic pressure
? Providing attachment sites for bacteriophages
? Providing a rigid platform for surface appendages-
flagella,fimbriae,and pili all emanate from the
wall and extend beyond it
? Play an essential role in cell division
? Be the sites of major antigenic determinants of
the cell surface。
? Resistance of Antibiotics
Wall-less forms of Bacteria,
? When bacteria are treated with 1) enzymes that are lytic for
the cell wall e.g,lysozyme or 2) antibiotics that interfere
with biosynthesis of peptidoglycan,wall-less bacteria are
often produced,
? Usually these treatments generate non-viable organisms,
Wall-less bacteria that can not replicate are referred to as
spheroplasts (when an outer membrane is present) or
protoplasts (if an outer membrane is not present),
? Occasionally wall-less bacteria that can replicate are
generated by these treatments (L forms),
Cell
membrane
? Site of biosynthesis of DNA,cell wall polymers and membrane lipids,Selective
permeability and transport of solutes into cells
? Electron transport and oxidative phosphorylation
? Excretion of hydrolytic exoenzymes
Mesosomes
? Mesosomes are specialized structures
formed by convoluted inveigh-nations of
cytoplasmic membrane,and divided into
septal and lateral mesosome,
Cytoplasm
? Composed largely of water,together with proteins,nucleic
acid,lipids and small amount of sugars and salts
? Ribosomes,numerous,15-20nm in diameter with 70S;
distributed throughout the cytoplasm; sensitive to
streptomycin and erythromycin site of protein synthesis
? Plasmids,extrachromosomal
genetic elements
? Inclusions,sources of stored
energy,e,g volutin
Plasmid Plasmids are small,circular/line，
extrachromosomal,double-stranded DNA
molecules。 They are capable of self-
replication and contain genes that confer
some properties,such as antibiotic
resistance,virulence factors。 Plasmids are
not essential for cellular survival,
Inclusions of
Bacteria
? Inclusions are
aggregates of various
compounds that are
normally involved in
storing energy
reserves or building
blocks for the cell,
Inclusions accumilate
when a cell is grown
in the presence of
excess nutrients and
they are often
observed under
laboratory conditions,
granulose
Nucleus
? Lacking nuclear
membrane,absence
of nucleoli,hence
known as nucleic
material or nucleoid,
one to several per
bacterium,
Capsules and slime layers
? These are structures surrounding the outside of the cell envelope,They
usually consist of polysaccharide; however,in certain bacilli they are
composed of a polypeptide (polyglutamic acid),They are not essential
to cell viability and some strains within a species will produce a capsule,
whilst others do not,Capsules are often lost during in vitro culture,
? Attachment
? Protection from phagocytic
engulfment,
? Resistance to drying,
? Depot for waste products,
? Reservoir for certain
nutrients,
? protection
Flagella
Monotrichate/Amphitrichate/Lophotrichate/Peritrichate
? Identification
of Bacteria
? Pathogenesis
? Motility of
bacteria
?Some bacterial species are mobile and possess
locomotory organelles - flagella,Flagella consist of a
number of proteins including flagellin
?The diameter of a flagellum is thin,20 nm,and
long with some having a length 10 times the
diameter of cell,Due to their small diameter,flagella
cannot be seen in the light microscope unless a
special stain is applied,Bacteria can have one or
more flagella arranged in clumps or spread all over
the cell,
Pili
? Pili are hair-like projections of the cell,They are
known to be receptors for certain bacterial viruses,
Chemical nature is pilin
? Classification and Function
a,Common pili or fimbriae,fine,rigid numerous,
related to bacterial adhesion
b,Sex pili,longer and coarser,only 1-4,related to
bacterial conjugation
Endospores
(spores)
? Dormant cell
? Resistant to adverse
conditions
- high temperatures
- organic solvents
? Produced when starved
? Contain calcium dipicolinate
DPA,Dipicolinic acid
? Bacillus and Clostridium
? Identification of
Bacteria
? Pathogenesis
? Resistance
Microscope
? Light Microscope
? Electron Microscope
? Darkfield Microscope
? Phase Contrast Microscope
? Fluorescence Microscope
? Cofocal Microscope）
Methods
Staining Methods
? Simple staining;
? Differential staining ( Gram
stain,Acid-fast stain),
? Special staining( Negative stain,
Spore stain,Flagella stain)
