17 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 17...

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PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 17 The Planctomycetes and Chlamydia
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http://schaechter.asmblog.org The Planctomyces are a phylogenetically unique group of stalked Bacteria • Four genera have been described: Planctomyces , Pirellula , Gemmata , and Isosphaera , but only 7 named species are available for laboratory study. • They are morphologically similar to the other stalked bacteria we have talked about. • The stalk of Planctomyces is made of protein and does not contain a cell wall or cytoplasm. • The stalk presumably functions in attachment but it is a much narrower and finer structure than the prosthecal stalk of Caulobacter . • Top: Cells of Planctomyces maris showing flagellum, stalk, and pilus. Note that a bud is developing from the nonstalked pole of the cell. Planctomyces have a life cycle in which a motile swarmer cell attaches to a surface, grows a stalk, and a new cell is generated by budding. • Bottom: Pirellula staleyi does not form a stalk, but instead excretes a holdfast substance that allows it to attach to surfaces. http://www.mbio.ncsu.edu/MB451
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www.palaeos.com/Eukarya/Eukarya.Origins.2.html The Planctomyces lack peptidoglycan and their cell walls are of an S-layer type • Some genes for peptidoglycan biosysnthesis remain in these organisms. • They are resistant to antibiotics that disrupt peptidoglycan synthesis, such as penicillin and cephalosporin. • Penicillin amended culture media can be used to isolate Planctomycetes . • Top: the cell walls (sometimes) have some rounded protrusions called "crateriform structures". Unclear at present what the function of these structure are. • Bottom: typical structure of a bacterial S-layer. • S-layer consists of protein containing large amounts of cystine and proline. • They are free-living aquatic oligotrophs that divide by budding, not binary fission.
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The Planctomyces have a membrane-bound nucleus • The major structural difference between eukaryotes and prokaryotes is a membrane-bound nucleus. •Left : Gemmata obscuriglobus , showing the nucleoid surrounded by a nuclear envelope. • The DNA is in a covalently closed, circular, and supercoilded form, typical of prokaryotes. • The nucleoid is highly condensed and partitioned from the cytoplasm by a true unit membrane.
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This note was uploaded on 08/04/2009 for the course BIOL 4125 taught by Professor Christner during the Spring '08 term at LSU.

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17 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 17...

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