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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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