Concept
Pili and fimbriae
Surface appendages for attachment and transfer
PY-lye and FIM-bree-ee
High-yield clue
Fimbriae mediate adhesion while the sex pilus mediates conjugative DNA transfer.
Overview
Thin protein appendages on the bacterial surface: short numerous fimbriae mediate adhesion to host cells and surfaces, while the longer conjugative (sex) pilus transfers DNA. Type IV pili also drive twitching motility.
Classification
- Proteinaceous surface appendage
- Fimbriae: adhesion
- Sex pilus: conjugation
- Type IV pili: twitching motility
Lab & identification clues
- Adhesin attachment-factor vocabulary
- Sex-pilus conjugation concept
- Pilus antigenic-variation vocabulary
Associations
- Colonization and biofilm attachment
- Conjugative plasmid transfer
- Neisseria pilus antigenic variation
Commonly confused with
- Flagella
- Capsule
Your notes
Original microbiology concept summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC/WHO topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment selection, infection-control instructions, or specimen-handling guidance.