2'4 Physiological Diversity of Microorganisms

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Lecture 3

• 2.4 Physiological Diversity of Microorganisms
• 2.5 Prokaryotic Diversity
• 2.6 Eukaryotic Microorganisms
• 4.4. Cell Morphology and the Significance of
  Being Small
• 4.5 Cytoplasmic Membrane Structure
• 4.6 Cytoplasmic Membrane Function
• 4.8 The Cell Wall of Prokaryotes Peptidoglycan
  and Related Molecules
• 4.9 The Outer Membrane of Gram-Negative Bacteria

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Carbon fixation

• autotrophs fix carbon from CO2
• include most phototrophs photoautotrophic
• heterotrophs get carbon from pre-existing
  organic compounds

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Domain Bacteria
root (common ancestor)
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Env-OP2

• not yet cultured known only by 16S rRNA
• SAR11 another clade identified by 16S

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Domain Archaea
methanogens halophiles acidophiles
hyperthermophiles
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Archaea

• tend to be extremophiles
• two clades of Env-marine isolates not found in
  extreme cnditions
• can grow over at 113oC
• can grow in cow rumens (produce methane)
• can grow at pH lt 0 (!)

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Domain Eukarya
multi-celled
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Endosymbiotic theory

• archaeal organism evolved a nuclear membrane,
  before or after engulfing a bacterium
• organisms developed a symbiosis which became an
  obligate relationship
• considerable sharing of genetic material
• similar mechanisms let to engulfing of a
  cyanobacterium to evolve chloroplasts

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Different Shapes
Fig. 4.11
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Different Sizes
SAR11 even smaller!
Figure 4.13
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Giant Bacteria
gut of tropical sugeon fish 16s related to
Clostridium (food pathogen) not cultured can
cultivate enough for sequencing depend on
nutrient-rich environment
Epulopiscium fishelsoni
Fig. 4.12
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Surface Area vs. Volume

• Size affects rate of nutrient and waste transport
  across the cell membrane
• Small size ? more efficient exchange, support of
  higher metabolic rate

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Phospholipid Bilayer
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Lipids in Bacteria and Archaea have different
chemical bonds
Ester - Bacteria
Ether - Archaea
Fig. 4.19
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Structure of Cytoplasmic Membrane
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Protein domain prediction

• based on amino acid sequence
• hydrophobic amino acid domains are expected to
  lie within the cytoplasmic membrane
• hydrophilic amino acid domains are expected to
  lie either on the cytoplasmic or outer side
• prediction confirmed by experimental studies

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Table 4.1 Comparative Permeability of Membranes
to Various Molecules
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Functions of Cytoplasmic Membrane

• Permeability Barrier
• small, uncharged (hydrophobic) molecules can pass
  through by diffusion
• Protein Anchor
• transport, generation of energy, chemotaxis
• Generation of proton motive force

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Transport proteins

• Transporters have substrate specificities
• generally, a given protein will transport
• one substrate
• a few similar substrates
• a class of substrates
• membranes possess multiple transporters

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Cell Walls of Bacteria

• Peptidoglycan is found only in bacteria
• Keeps cells from lysing, due to turgor pressure

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Gram staining

• cells are stained purple and then washed
• Gram positive cells show purple
• Gram negative cells are colourless
• pink counter-stain
• Gram positive remain purple
• Gram negative cells stain pink
• Reason outer membrane of Gram negative cells
  resists purple stain

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Protoplast Formation
Lysozyme -- a protein that breaks 1,4-glycosidic
bonds in peptidoglycan
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Peptidoglycan Structure
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peptide chains vary among species
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Teichoic Acids
Acidic polysaccharides found in gram positive
cell walls
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Gram Positive Cell Wall
Fig 4.32b
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Archaeal Pseudopeptidoglycan
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Lipopolysaccharide (LPS)
Only in gram negative bacteria Part of the outer
membrane Help protect organism from
environment Often cause of host reactions and
symptoms of infectious disease
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Gram Negative Outer Membrane
Porins - proteins that allow small molecules to
cross membrane -- specific and non-specific