Pronunciation: pi'lus, pi'li
A fine filamentous appendage, somewhat analogous in function to the flagellum, which occurs on some bacteria. Although they can be chemically similar to flagella, pili consist only of protein and are shorter, straighter, and more numerous. Specialized pili (F pili, I pili, and other conjugative pili) seem to mediate bacterial conjugation and bacterial attachment to host cells during the infective process.
See Also: conjugative plasmid
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Examples: glitazone, GI cocktail, etc.