Bacterial cytoskeleton PDF

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Summary

Overview of the Bacterial cytoskeleton and how cell shape in bacteria is controlled...

Description

Bacterial cytoskeleton 

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Eukaryotic cells have 4 main types of cytoskeletal o microtubules, composed of tubulin o microfilaments, composed of actin o intermediate filaments o molecular motors Bacterial cytoskeletal elements o tubulin homologue: FtsZ o actin homologue: MreB, Mbl proteins; ParM, MamK o intermediate filaments: CreS o molecular motors – not found in bacteria

Cell shape in Bacteria is controlled by: 

The Actin Homologue, MreB o Actin is involved in processes such as locomotion, cell growth and cytokinesis o MreB + Mbl function in cell growth and shape o MreB mutants are spherical o Mbl mutants are deformed o MreB polymerises ito filaments in the presence of ATP or GTP o Filaments = helical or dynamic patch o MreB directs the cell shape  MreC is used for spacial organization of components of the peptidoglycan synthesis holoenzyme in the periplasm  MreB directs the localization of precursor synthesis in the cytosol o MreB In bacteria  There is a striking correlation between nonspherical shape on MreB  Rod shape bacteria is due to the presence of mreB EXCEPT in Agrobacterium/Rhizobacterium and Mycobacterium/Corynebacterium  Spherical bacteria contain no MreB

Rod shaped bacteria

most

exceptions...

Part of the cell wall synthesis takes place throughout the entire cell length (alongside MreB cables)

Part of the cell wall synthesis takes place at the poles (NO MreB cables)

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Tubulin homologue – FtsZ controls cell division in bacteria o Polymerization is GTP dependent o With help of accessory proteins the FtsZ ring is formed o FtsZ controls Bacterial cell division  FtsZ polymerises into a ring structure  Recruits other proteins which are involved in new cell wall synthesis at the division site

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Intermediate filaments in bacteria o CreS = intermediate filament o CreS mutants lost curved shape o CreS forms a filament alongside the curved shape of Calobacter cells which are aquatic bacterium with a curved rod shape

Other functions in bacterial cytoskeleton is controlled by: 

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ParM o Actin homologue o Mediates plasmid partitioning o A mechanisms analogous to that used by microtubules during eukaryotic mitosis MamK o Actin homologue

Controls the organization of magnetite particles in magnetosomes...