A holdfast - which is not always an easily visualized, discrete structure - is often present at the distal end of an appendage or at one end of the cell. Often form homologous aggregations, rosettes or bouquets, by joining at the holdfasts. Some species have a dimorphic life cycle: a sessile mother cell buds;) the bud develops into a swarmer that is motile by means of a flagellum; after maturation, the swarmer loses its flagellum and becomes a sessile, budding mother cell.

Produce crateriform surface structures (surface pits 12 nm in diameter, circumscribed by a grommet with a 30-36 nm outside diameter) and pili in characteristic patterns.