Cell Component
pilus
pi·lus [ pahy-luhs ]
Subclass of:
Cell Surface Extensions; Bacterial Structures
Etymology:
Latin pilus = a hair
Definitions related to bacterial fimbria:
  • (pilus) A proteinaceous hair-like appendage on the surface of bacteria ranging from 2-8 nm in diameter.
    Gene Ontology Dictionary
    Gene Ontology Consortium, 2021
  • (pilus) Minute filamentous appendages of certain bacteria associated with antigenic properties and sex functions of the cell.
    CRISP Thesaurus
    National Institutes of Health, 2006
  • (fimbriae, bacterial) Thin, hairlike appendages, 1 to 20 microns in length and often occurring in large numbers, present on the cells of gram-negative bacteria, particularly Enterobacteriaceae and Neisseria. Unlike flagella, they do not possess motility, but being protein (pilin) in nature, they possess antigenic and hemagglutinating properties. They are of medical importance because some fimbriae mediate the attachment of bacteria to cells via adhesins (ADHESINS, BACTERIAL). Bacterial fimbriae refer to common pili, to be distinguished from the preferred use of pili, which is confined to sex pili (PILI, SEX).
    NLM Medical Subject Headings
    U.S. National Library of Medicine, 2025
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