SURFACE APPENDAGES - tumbling motion. Flagella may serve as...

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SURFACE APPENDAGES Bacteria may or may not possess surface appendages that provide the organism with the ability to be motile or to transfer genetic material or to attach to host tissues. These appendages are outlined below: 1. Flagella : These are the organs of motility. Flagella are composed of flagellins (proteins) that make up the long filament. This filament is connected to a hook and rings that anchor the flagella in the cell wall. In Gram-positive bacteria, there are two rings attached to the cytoplasmic membrane; in Gram-negative cells, an additional two rings are found in the outer membrane. Flagella may be up to 20 µm in length. Some bacteria possess a single polar flagellum (monotrichous), others have several polar flagella (lophotrichous), others have several flagella at each end of the cell (amphitrichous), and still others have many flagella covering the entire cell surface (peritrichious). Counterclockwise rotation of the flagella produces motility in a forward motion; clockwise rotation produces a
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Unformatted text preview: tumbling motion. Flagella may serve as antigenic determinants (e.g. the H antigens of Gram-negative enteric bacteria). 2. Pili : These surface appendages come in two distinct forms having distinct purposes. Pili (or fimbrae) may also provide antigenic determinants (e.g. the M protein of S. pyogenes ). 1. Sex pili : This form of pilus can be relatively long but is often found in few numbers, generally 1 to 6, protruding from the cell surface. These structures are involved in conjugation, the transfer of genetic information from one cell to another. These structures can also provide the receptor for certain male-specific bacteriophages. 2. Common pili : This form of pilus is usually relatively short and many (about 200) and can be found covering the cell surface. These structures provide the means for attachment to host cells (e.g. epithelial cells) and often play an important role in colonization (e.g. N. gonorrhoeae )....
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SURFACE APPENDAGES - tumbling motion. Flagella may serve as...

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