| sex pili | <cell biology> Fine filamentous projections (pili) on the surface of a bacterium that are important in conjugation. Often seem to be coded for by plasmids that confer conjugative potential on the host, in the case of the f plasmid, the F pili are 8-9nm diameter and several microns long, composed of pilin. Whether the pili merely serve to establish and maintain adhesive contact between the partners in conjugation or whether DNA is actually transferred through the central core of the pilus is still unresolved, although a simple adhesion role is more generally accepted. (18 Nov 1997) |
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| I pili | See: pilus. Pili multigemini, the presence of several hairs in a single follicle. R pili, specialised pili found on bacterial cells, similar to F pili and associated with R plasmids. Pili torti, a condition in which many hair shafts are twisted on the long axis, congenital or acquired as a result of distortion of the follicles from a scarring inflammatory process, mechanical stress, or cicatrizing alopecia; the hair shafts resemble spangles in reflected light, are brittle, and break at varying lengths with many areas appearing bald with a dark stubble; as a developmental defect it can be manifested in such syndromes as Bjornstad's, Crandall's, and Menkes'. Synonym: twisted hairs. (05 Mar 2000) |
| F pili | See: pilus. F pilus, a structure responsible for attachment of individual male (F+) to female (F-) bacteria, forming conjugal pairs. (05 Mar 2000) |