Lecture outline

1
Lecture outline

• History/Introduction
• Microbiological Techniques/ Diversity
• Diversity/ Structure and function
• Prokaryotic structure and function
• Nuclear structure, cell walls etc.
• Prokaryotic structure and function
• Prokaryotic structure and function
• Bacterial growth.
• Bacterial Genetic systems (LK)

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Simplified Bacterial Cell
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Cell Surface structures and Cell walls

• A. Flagellae
• B Pili and fimbrae
• C. Capsules
• D. Cell Walls, membranes and Peptidoglycan
• Membrane structure and function
• Gram Positive. Teichoic acids
• Gram negative. Outer membrane/ Lipopolysaccharide

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Cell Surface structures and Cell walls

• A. Bacterial flagellae
• Helical. Several times the length of the cell
• Single polar - E.coli as shown
• two polar - Pseudomonas spp. Very motile
• Axial filaments. Spirochetes.
• Subunits of flagellin protein.
• Helix arrangement. Self assembly.
• At least 12 genes control the basal components in
  E.coli.

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Cell Surface structures and Cell walls cont

• Mechanism of motility
• Rotate rigidly, motor in cell membrane
• ATP not hydrolysed. Involves proton motive force
  in respiring membrane
• Multiple flagellae rotate in bundles

(Berg.H C. 1973)
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Bacterial flagellum structure and mechanism
Flagellum rotates via motor in active membrane
Gram Positive
Gram Negative
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Cell Surface structures and Cell walls cont

• Chemotaxis
• Motile bacteria swim toward attractants
• Positive and negative chemotaxis
• Sense environment. Surface receptors
• CHEMORECEPTORS
• over 20 recognised in E.coli

Random motion
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Cell Surface structures and Cell walls cont

• B. Pili and fimbrae.
• Filamentous appendages up to 30 ?m long and
  20-30nm thick
• Self assembly
• Adhesion to surfaces
• Sex pili involved in conjugation
• C. Capsules and slime
• External layer of polysaccharide (except B
  antracis D-glutamic acid polymer)
• C/N nutrition dependent
• Homo or hetero polysaccharide (usually amino
  hexoses)
• Serves to protect cells eg phagocytosis,
  dessication etc.

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D. Cell Walls, membranes and Peptidoglycan

• Membrane defines INSIDE and OUTSIDE
• Cell wall constructed OUTSIDE
• Wall is a RIGID structure. PEPTIDOGLYCAN
• Various polymers are interlinked to make ONE big
  polymer.
• Serves to protect the cells from harsh
  environments
• TEICHOIC ACIDS found only in GRAM positive cells
• either glycerol phosphate polymer
• or ribitol phosphate polymer

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Gram-negative Cell Wall Structure
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Gram-negative Cell Wall Structure
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Membrane structure and function
Glycerol 3-phosphate HYDROPHYLIC

• Cytoplasmic or Plasma membrane
• Glycerophospholipids fatty acid esters of
  glycerol 3-phosphate
• Arranged in fluid bilayer
• Many proteins arranged in membrane
• substrate transport functions
• respiration
• secretion and cell wall growth enzymes

Long chain fatty acid HYDROPHOBIC
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Gram Positive and Gram Negative Cell Types
Outer-membrane
GRAM POSITIVE
GRAM NEGATIVE
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Gram-positive Cell Wall Structure
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Gram-positive Cell Wall Structure
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Gram-negative Cell Wall Structure
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Peptidoglycanstructure
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Peptidoglycan structure
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Lipopolysaccharidestructure