4.10 Flagella and Motility

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Lecture 4

• 4.10 Flagella and Motility
• 4.11 Gliding Motility
• 4.12 Bacterial Responses Chemotaxis, Phototaxis,
  and other Taxes
• 4.13 Bacterial Cell Surface Structures and Cell
  Inclusions
• 4.14 Gas Vesicles
• 4.15 Endospores

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The Flagellum
1000 H / rotation
gt 40 genes involved
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Flagellar motion

• gt 40 genes involved, include regulators
• movement driven by propeller-like rotation
• can propel cells up to 60 cell lengths/s
• equivalent of 2.5x faster than a cheetah!
• expensive process must confer strong selective
  advantage

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Steps in Biosynthesis of Flagella
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Types of Flagellar Arrangements
Run
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Motility in non-aqueous environments

• polysaccharide slime layer
• secreted slime used to pull cell along a surface
• special proteins in the outer membrane act like
  feet, which are activated by inner membrane
  proteins resulting in crawling

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Absence of chemical attractant
Fig. 4.46a
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Presence of chemical attractant
chemical gradient sensed in a temporal manner
Fig. 4.46b
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Measuring Chemotaxis
attractant
repellent
control
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Other types of taxes

• phototaxis - light
• aerotaxis - oxygen
• osmotaxis - osmotic strength

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Cell structures and inclusions

• fimbriae - aid cell adherence to surfaces
• pili - conjugation, attachment to host cell
• glycocalyx - polysaccharide layer outside cell,
  attachment to host cells, protection from host
  immune system, resistance to dessication
• polyhydroxyalkanoate deposits - intracellular
  carbon and energy store
• polyphosphate - intracellular reserves
• elemental sulfur - intracellular granules
• magnetosomes - intracellular magnetite crystals
  (iron oxide)
• gas vesicles - cell buoyancy

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Poly-ß-hydroxybutyrate (PHB)
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Poly-3-hydroxybutyrate (PHB)


CH3
O
OCHCH2C
n 25,000

• Carbon and energy reserve
• Accumulates intracellularly when carbon source is
  not limiting for growth
• Can be utilized under carbon starvation
  conditions
• Biodegradable bioplastics
• Production does not contribute greenhouse gases

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Gas Vesicle Proteins
watertight, gas-permeable structure (hydrophobic
proteins)
Fig. 4.58
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Endospores
Resistant to heat, radiation, acids, drying,
chemicals Do not contain RNA Dehydrated (only
10-30 H2O as vegetative cell)
Fig. 4.62
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Dipicolinic acid
Characteristic of endospores
Fig. 4.61
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How long can spores survive?

• See page 97, report that 250 million year old
  spores have been revived
• These spores were preserved in salt crystals of
  Permian age
• bacteria revived from brine deposits
• environmental contaminants prevented by
  steriliziation controls for sterility

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Endospore Formation

• triggered by sub-optimal growth conditions (heat,
  starvation, dessication, etc.)
• return to optimal conditions sees germination of
  spores within minutes
• studied by isolating mutants that do not form
  spores and studying at what point sporulation is
  blocked

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Sporulation
8 h for entire process
Initiated when nutrients limiting
Stages determined by mutational analysis
200 genes involved
SASP small acid-soluble spore proteins Cortex
is composed of peptidoglycan Exosporium is a thin
protein covering