hamus

Hamus, or hami (plural), are a class of archaeal cell surface appendages described in certain extremophiles. The structure resembles a grappling hook: a basal anchoring point embedded in the cell envelope, a flexible shaft, and a distal hook with barbs. These filaments project from the cell surface and often appear in multiple copies per cell. The exact composition is proteinaceous, and the structures are produced by a dedicated set of genes distinct from bacterial pili.

The proposed function of hamus is primarily adhesion. They facilitate attachment to inorganic surfaces and to other cells, contributing to surface colonization and biofilm formation in extreme environments such as hypersaline lakes or hydrothermal systems. By enabling stable attachment, hamus may help archaeal cells withstand fluid shear and compete for limited resources.

Hamus were first described through electron microscopy studies of certain archaeal cultures. Research continues to characterize their assembly, regulation, and distribution across archaeal taxa, as well as their ecological roles. While not universal to all archaea, hamus represent a notable example of the diversity of surface appendages in this domain and offer potential insights for nanostructure engineering and biofilm biology.

See also: archaeal pili, biofilm, extremophiles.