Peptidoglycan Synthesis
Transport of peptidoglycan precursors across the
cytoplasmic membrane to the growing point of the cell wall
The transpeptidation reaction that lead to the final
cross-linking of two peptidoglycan chains
Penicillin inhibits this reaction
The majority of motile prokaryotes
move by means of flagella
Flagellar Arrangements
Peritrichous
Polar
Lophotrichous
The E,coli
Flagellar
Structure
Bacterial Behavior
Chemotaxis,Phototaxis,and Other Taxes
? Prokaryotes encounter gradients of physical
and chemical agents in nature,and the motility
machinery in the cell is designed to respond in
a positive or negative way to these gradients
by directing the movement of the cell either
toward or away from the signal molecule,
respectively.
? Such directed movements are called TAXiS.
? Chemotaxis,a response to chemicals.
? Phototaxis,a response to light.
Chemotaxis in Bacteria
? Chemotaxis is the
movement of an
organism toward (an
attractant) or away from
(a repellent) a chemical.
The Chemotaxis
Process
(a) In the absence of a
chemical attractant the
cell swims randomly
in runs,changing
direction during
tumbles.
(b) In the presence of an
attractant runs become
biased,and the cell
moves up the gradient
of the attractant.
Mechanism of Chemotaxis
MCPs,methyl-accepting chemotaxis proteins
Phototaxis
? Accumulation of the phototrophic bacterium at light wavelengths at
which its pigments absorb.
? Phototaxis of an entire colony toward the light source on the right.
Bacterial Cell Surface Structures
and Cell Inclusions
? Fimbriae and Pilli
? Paracrystalline layers (S-layers)
? Capsules and Slime Layers (Glycocalyx)
? Inclusions and Storage Products
? Gas Vesicles
? Endospores
Fimbriae (菌毛 )and Pilli(纤毛 )
Paracrystalline layers (S-layers)
? Many prokaryotes contain a
cell surface layer composed
of a two-dimensional array
of protein called S-layer.
? S-layer has been detected in
representatives of virtually
every phylogenetic grouping
of bacteria and nearly
universal among Archaea.
? In some species of Archaea,
the S-layer is also the cell
wall.
Capsules and Slime Layers
(Glycocalyx or 多糖包被 )
Glycocalyx:
Polysaccharide-
containing
material lying
outside the cell.
Capsules:
Rigid layers of
glycocalyx.
Slime Layers:
Flexible layers of
glycocalyx.
Inclusions and Storage Products
? Polyhydroxyalkanoates (carbon source and energy storage
materials)
? Glycogen (carbon source and energy storage materials)
? Polyphosphate
? Elemental sulfur
? Magnetosomes (magnetotaxis of Aquaspirillum
magnetotacticum)
Polyhydroxyalkanoates or PHA
?Mostly
hydrophobic;
?Chiral monomers;
?Great structure
varieties;
?Among PHA,
polyhydroxybutyrate
or PHB is the most
common;
?Molecular weights
range from 10,000 to
several millions.
Elemental sulfur and Magnetosomes
? Sulfur globules in Magnetic particles of Fe3O4 Isolated
Chromatium buderi,from Aquaspirillum magnetotacticum
Gas Vesicles (气泡）
A,Gas vesicles purified from Microcyclus aquaticus (水生短周期菌 ).
B,Gas vesicles are arranged in bundles in Microcystis.
C,The vesicle group in Anabaaaena flos-aquae (鱼腥藻 ) together
as phase bright objects that scatter light.
A B C
Structure of Gas Vesicles
Gas vesicles contain only two different types of protein,
(GvpA and GvpC)
Morphology of Endospores (孢子）
A,Terminal,B,Subterminal,C,Central
A B C
Endospore Life Cycle and Structure
A,Life Cycle of endospore
B,Formation of endospore in Bacillus megaterium
C,Mature free endospore
A
B C
Transport of peptidoglycan precursors across the
cytoplasmic membrane to the growing point of the cell wall
The transpeptidation reaction that lead to the final
cross-linking of two peptidoglycan chains
Penicillin inhibits this reaction
The majority of motile prokaryotes
move by means of flagella
Flagellar Arrangements
Peritrichous
Polar
Lophotrichous
The E,coli
Flagellar
Structure
Bacterial Behavior
Chemotaxis,Phototaxis,and Other Taxes
? Prokaryotes encounter gradients of physical
and chemical agents in nature,and the motility
machinery in the cell is designed to respond in
a positive or negative way to these gradients
by directing the movement of the cell either
toward or away from the signal molecule,
respectively.
? Such directed movements are called TAXiS.
? Chemotaxis,a response to chemicals.
? Phototaxis,a response to light.
Chemotaxis in Bacteria
? Chemotaxis is the
movement of an
organism toward (an
attractant) or away from
(a repellent) a chemical.
The Chemotaxis
Process
(a) In the absence of a
chemical attractant the
cell swims randomly
in runs,changing
direction during
tumbles.
(b) In the presence of an
attractant runs become
biased,and the cell
moves up the gradient
of the attractant.
Mechanism of Chemotaxis
MCPs,methyl-accepting chemotaxis proteins
Phototaxis
? Accumulation of the phototrophic bacterium at light wavelengths at
which its pigments absorb.
? Phototaxis of an entire colony toward the light source on the right.
Bacterial Cell Surface Structures
and Cell Inclusions
? Fimbriae and Pilli
? Paracrystalline layers (S-layers)
? Capsules and Slime Layers (Glycocalyx)
? Inclusions and Storage Products
? Gas Vesicles
? Endospores
Fimbriae (菌毛 )and Pilli(纤毛 )
Paracrystalline layers (S-layers)
? Many prokaryotes contain a
cell surface layer composed
of a two-dimensional array
of protein called S-layer.
? S-layer has been detected in
representatives of virtually
every phylogenetic grouping
of bacteria and nearly
universal among Archaea.
? In some species of Archaea,
the S-layer is also the cell
wall.
Capsules and Slime Layers
(Glycocalyx or 多糖包被 )
Glycocalyx:
Polysaccharide-
containing
material lying
outside the cell.
Capsules:
Rigid layers of
glycocalyx.
Slime Layers:
Flexible layers of
glycocalyx.
Inclusions and Storage Products
? Polyhydroxyalkanoates (carbon source and energy storage
materials)
? Glycogen (carbon source and energy storage materials)
? Polyphosphate
? Elemental sulfur
? Magnetosomes (magnetotaxis of Aquaspirillum
magnetotacticum)
Polyhydroxyalkanoates or PHA
?Mostly
hydrophobic;
?Chiral monomers;
?Great structure
varieties;
?Among PHA,
polyhydroxybutyrate
or PHB is the most
common;
?Molecular weights
range from 10,000 to
several millions.
Elemental sulfur and Magnetosomes
? Sulfur globules in Magnetic particles of Fe3O4 Isolated
Chromatium buderi,from Aquaspirillum magnetotacticum
Gas Vesicles (气泡）
A,Gas vesicles purified from Microcyclus aquaticus (水生短周期菌 ).
B,Gas vesicles are arranged in bundles in Microcystis.
C,The vesicle group in Anabaaaena flos-aquae (鱼腥藻 ) together
as phase bright objects that scatter light.
A B C
Structure of Gas Vesicles
Gas vesicles contain only two different types of protein,
(GvpA and GvpC)
Morphology of Endospores (孢子）
A,Terminal,B,Subterminal,C,Central
A B C
Endospore Life Cycle and Structure
A,Life Cycle of endospore
B,Formation of endospore in Bacillus megaterium
C,Mature free endospore
A
B C
