2-Structure_and_Function_Jan15-17

Best studied in clostridium species and bacillus

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Unformatted text preview: avigaAon (photoreceptor) Not photosyntheAc Purple: Photosynthesis, supplies sugar to the green Not moAle hbp://schaechter.asmblog.org/schaechter/2014/01/how- do- they- make- it- work- genomic- revelaAons- on- a- bacterial- consorAum.html 59 Surface appendages •  In addiAon, prokaryotes may have other surface appendages: flagella and fimbriae. •  Flagella are used for locomoAon (moAlity). Usually 15- 20 μm long. The flagella of Archaea are sAll not fully understood. •  Fimbriae are involved primarily in the abachment of the microorganism to surfaces. They form rigid, rod- like structures. Usually ≤ 4 μm long. Found primarily on Gram- negaAve bacteria. 60 Brock Biology of Microorganisms, 13th EdiAon. Fimbriae of Gram- negaAve bacteria •  The best studied fimbriae is the P fimbriae produced by uropathogenic E. coli. •  In contrast to flagella, fimbriae of Gram- negaAve bacteria grow from the base. The assembly requires two proteins: the chaperone and the usher. •  The subunits are assembled by strand exchange (like puzzle pieces). •  Adhesion can be mediated by: –  the main subunits –  a specialized subunit at the Ap (as for the P fimbriae). Fimbriae of Gram- posiAve bacteria •  In Gram- posiAves, adhesion to surfaces is generally carried out by surface adhesins, consisAng of only one protein. Such adhesins mediate very close abachment. •  Fimbraie of Gram- posiAve bacteria are assembled by sortases and abach to the pepAdoglycan. Fimbriae •  Gram- posi/ve •  Gram- nega/ve –  Anchored in the pepAdoglycan –  Anchored in the outer membrane –  Composed of pilin proteins –  Composed of pillin proteins –  Covalently- linked to one another –  Not covalently bound to one another (strand exchange) –  Assembled enzymaAcally by sortases. –  Accessory proteins are needed, encoded with the fimbriae pilin genes . 63 Endospore •  Endospores – endo, internal...
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