flagellumbearing

Flagellumbearing, or flagellum-bearing, is the biological characteristic of possessing one or more flagella, slender, whip-like appendages used for locomotion. The term is applied across life domains, including bacteria, archaea, and certain eukaryotes such as algae and animal sperm. Flagellated organisms may rely on their flagella for directed movement toward nutrients, away from toxins, or toward favorable light or chemical cues.

In bacteria, flagella are complex macromolecular machines anchored in the cell envelope. A basal body powers rotation of a hollow filament called the flagellin filament, driven by a rotary motor. Flagellar arrangements are diverse: monotrichous (single flagellum), amphitrichous (one at each end), lophotrichous (tufts at one end), and peritrichous (distributed over the surface). Flagellar motility supports chemotaxis and environmental exploration and can influence colonization, nutrient acquisition, and virulence in some species. The flagellin protein itself is a key antigen recognized by host immune systems in many animals.

In eukaryotes, flagella are structurally distinct from bacterial ones. They typically feature a 9+2 axonemal arrangement of microtubules powered by dynein motors, producing whip-like beating that propels the cell. Examples include sperm cells and certain single-celled algae. Archaea possess analogous structures called archaella, which are superficially similar to bacterial flagella but are built from different protein families and share separate evolutionary origins.

Identification of flagellumbearing involves microscopy, motility assays, and genetic analyses of flagellin or archaellin genes. Flagellum presence can influence ecological interactions, pathogenic potential, and motility strategies across taxa.