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.

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Presentation transcript:

Lecture 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

The Flagellum 1000 H + / rotation > 40 genes involved

Flagellar motion > 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

Steps in Biosynthesis of Flagella

Run Types of Flagellar Arrangements

Motility in non-aqueous environments 1.polysaccharide “slime layer” —secreted slime used to pull cell along a surface 2.special proteins in the outer membrane act like feet, which are activated by inner membrane proteins resulting in “crawling”

Absence of chemical attractant Fig. 4.46a

Presence of chemical attractant Fig. 4.46b chemical gradient sensed in a temporal manner

Measuring Chemotaxis control repellent attractant

Other types of taxes phototaxis - light aerotaxis - oxygen osmotaxis - osmotic strength

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

Poly-ß-hydroxybutyrate (PHB)

Poly-3-hydroxybutyrate (PHB) uCarbon and energy reserve uAccumulates intracellularly when carbon source is not limiting for growth uCan be utilized under carbon starvation conditions uBiodegradable bioplastics uProduction does not contribute greenhouse gases CH 3 —O·CH·CH 2 ·C— O [] n ~ 25,000

Gas Vesicle Proteins Fig watertight, gas-permeable structure (hydrophobic proteins)

Endospores Fig Resistant to heat, radiation, acids, drying, chemicals Do not contain RNA Dehydrated (only 10-30% H 2 O as vegetative cell)

Dipicolinic acid Fig Characteristic of endospores

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

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

Sporulation 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 8 h for entire process