Chapter 1 Morphology and properties of bacteria
Chapter 1 Morphology and properties of bacteria
Belong to the prokaryote kingdom,the absence of a nuclear membrane and mitotic apparatus and the absence of othe
r organelle besides the ribosome.
Belong to the prokaryote kingdom,the absence of a nuclear membrane and mitotic apparatus and the absence of othe
r organelle besides the ribosome.
Section 1 Size and shapes of bacteria
The unit of measurement is micrometer (μm)
Sizes
basic shapes
• Spherical: coccus• Straight rod: bacillus• Curved or spiral: vibrio or spirillum• Uncharacteristic (e.g., filamentous, pleomorphic, et
c.)
Arrangements
• cocci
In one plane: Diplococcus Streptococcus
In two planes: Tetrad
In three planes: Sarcina
In random planes:Staphylococcus
Cell Arrangement
Coccus Division in plane
( Diplococcl )
( Chain )
Neisseria
StreptococcusDivision in two planes
( Tetrad )
Sarcina
Division in three planes
( Sarcina )
Staphylococcus( Clustor )
Division in Multi- planes
Tetrad
( 1 ) diplococcus
S. pneumoniae gonococcus
( 2 ) streptococcus
α-hemolytic streptococcus
( 3 ) staphylococcus
S. aureus
Arrangements
• Bacilli
Only in one plane
Bacillus
Streptobacillus
Coccobacillus
bacillus dysenteriae (gram staining)
Bacillus tuberculosis(acid fast stain)
Arrangements
• Spiral bacteria
in single cells
Section 2 Structures of Bacterial cells
• BasicCell wallCellular membraneCytoplasmnucleoid• SpecialCapsuleFlagellumPilusSpore
Bacterial structure
Cell wall-Components
Cell wall-Components
• Peptidoglycan Backbone: alternating N-acetylmuramic acid
(NAM) and N-acetylglucosamine (NAG)
A set of identical tetrapeptide side chains
A set of identical pentapeptide cross bridges(G+)
peptidoglycan
N-acetylglucosamineN-acetylmuramic acid
Staphylococcus aureus金黄色葡萄球菌
E.coli大肠杆菌
Lysozyme breaks this bond
pentaglycine bridge
L-alaD-gluL-lysD-alaD-ala
L-alaD-glu
m-DAPD-alaD-alapenicillin
Cell wall-Components
•Teichoic acid: Organisms: G+ bacteria
Types: the wall teichoic acidthe membrane teichoic acid
Function: acts as a specific antigenic determinantRelation to pathogenicity
Wall teichoic acid
(LTA)
Cell wall-Components
• Outer membrane
Organisms: G- bacteria Composition: Lipoprotein Lipid bilayer Lipopolysaccharide (LPS): lipid A core polysaccharide O-polysaccharide
Outer membrane
Functions:
prevents toxic materials from entering
functions as a harmful endotoxin
possesses the property of antigenic specificity
GlN-MurGlN-MurGlN-MurGlN-MurGlN-Mur GlN-Mur GlN-Mur Gln-Mur
GlN-MurGlN-MurGlN-MurGlN-MurGlN-Mur GlN-Mur GlN-Mur Gln-Mur
GRAM POSITIVEGRAM POSITIVE
GRAM NEGATIVEGRAM NEGATIVE
CytoplasmCytoplasm
CytoplasmCytoplasm
GlN-MurGlN-MurGlN-MurGlN-MurGlN-Mur GlN-Mur GlN-Mur Gln-Mur
Lipoteichoic acid Peptidoglycan-teichoic acid
Cytoplasmic membrane
Inner (cytoplasmic) membrane
Outer Membrane
Lipopolysaccharide
GlN-Mur GlN-Mur GlN-Mur GlN-Mur
Porin
Braun lipoprotein
Peri
plas
mic
spa
ce
Properties of the cell walls of Gram-positive and Gram-negative bacteria
Properties Gram-positive Gram-negative
Peptidoglycan Thicker Thinner
Teichoic acid Yes No
LPS (endotoxin) No Yes
Outer membrane No Yes
Results of enzyme digestion Protoplast Spheroplast
Cell wallFunctions• gives the bacterium its shape • Protecting the cell• Constituting major surface
antigens• Permitting the free diffusion of
low-molecular-weight hydrophilic compounds
• Having pathogenic material
Gram-positive
Gram-negative
The mechanism of some antibiotics
and enzymes killing bacteria • penicillin: Binds to transpeptidase and blocks the formation of whole cell wall of Gram-positive bacteria
•Lysozyme: Destroys the peptidoglycan by cleaving the β-1,4 glycosidic bonds between NAM and NAG
G- G+
N-acetylglucosamineN-acetylmuramic acid
Staphylococcus aureusE.coli
Lysozyme breaks this bond
pentaglycine bridge
L-alaD-gluL-lysD-alaD-ala
L-alaD-glu
m-DAPD-alaD-alapenicillin
G+ and G-
• Penicillin and cephalosporin
• Results of enzyme digestion:Protoplast Spheroplast
L forms
• Definition: bacteria that their peptidoglycan is destroyed or lost by various factors but they can survive under highly osmotic environment.
• Types: Protoplasts(G+) and spheroplasts (G-)• Shape: polymorphism • Staining property: gram-negative • Grow environment: high osmotic • Pathogenicity: chronic
A.Colony of normal bacteria B.fried egg colony of L-form bacteriaC.Granular colony of L-form bacteria
D.filamentous colony of L-form bacteria
• L forms are able to grow and divide
• Caused by antibiotic
• Some L forms can revert to the normal form upon removal of the inducing stimulus
producing chronic infections,being resistant to antibiotic treatment.
B.Cell membrane(Cytoplasmic membrane)
• Composition: composed primarily of proteins and lipids.
• It is a thin,elastic cytoplasmic
membrane,which is 5 ~ 10nm thick
• Visible in some ultrathin sections
• Examined with the electron
microscope
Function
active transport
respiratory chain component
biosynthesis
excretion
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