Definition

1. Noun (Biology/Microbiology):
   • A hairlike appendage found on the surface of many bacteria and some other cells. Pili (plural) are primarily involved in adhesion to surfaces, including host tissues, and in the transfer of genetic material between bacterial cells (a process called conjugation).
2. Noun (Obsolete/Rare Biological Term):
   • A single hair; a filamentous growth. This usage is archaic and largely superseded by the more common term "hair."

Usage Examples

• Noun (Microbiology):
  • The bacterium uses its pilus to attach to the host cell.
  • Conjugation is mediated by a specialized structure called a sex pilus.
• Noun (Archaic: Hair):
  • The old text described a pilus growing from a mole. (This example illustrates the historical usage.)

Advanced Usage

• "Fimbria" vs. "Pilus": In bacteriology, "fimbriae" (singular: fimbria) are often used interchangeably with "pili" to describe hair-like structures for attachment. However, a "sex pilus" or "conjugative pilus" is a specific type involved in DNA transfer.
• "Pilus Assembly": Refers to the complex biological process by which these protein structures are built and extended from the cell surface.

Variants and Related Words

• Pili (n): The plural form of pilus.
  • The surface of the cell was covered in numerous pili.
• Piliated (adj): Describing a cell that possesses pili.
  • The piliated strain showed much stronger adhesion.

Synonyms

• Fimbria (n, Microbiology): A hairlike appendage, often shorter than a pilus, used for attachment.
• Hair (n, General): The common term for a filament growing from the skin of a mammal. (This is a synonym only for the archaic meaning.)

Related Phrases/Phrasal Verbs

(Not typically applicable for this technical noun.)

Related Idioms

(Not typically applicable for this technical noun.)

Noun

1. hairlike structure especially on the surface of a cell or microorganism
2. any of the cylindrical filaments characteristically growing from the epidermis of a mammal
   • there is a hair in my soup