Bacterial Phylum Verrucomicrobiota

The phylum Verrucomicrobiota comprises at least four characterized orders, with most species classified within the order Verrucomicrobiotales. Members of this phylum are either aerobic or facultatively aerobic, with the ability to ferment sugars. A notable exception is the genus Methylacidiphilum, which consists of aerobic methanotrophs. Additionally, some Verrucomicrobiota establish symbiotic relationships with protists. These bacteria are widely distributed across various environments, including freshwater, marine habitats, forest soils, and agricultural lands.

Like the Planctomycetes, Verrucomicrobiota possess membrane-bound intracellular structures. However, a distinctive feature of Verrucomicrobiota is the presence of cytoplasmic extensions called prosthecae. These appendages are supported by peptidoglycan in their cell walls, distinguishing them from Planctomycetes.

The genera Verrucomicrobium and Prosthecobacter are notable for producing multiple prosthecae on each cell. In contrast to Caulobacter, which develops a single prostheca and releases flagellated swarmer cells that lack prosthecae, Verrucomicrobium and Prosthecobacter undergo symmetrical cell division, resulting in both mother and daughter cells possessing prosthecae at the time of division. The name Verrucomicrobium is derived from Greek, meaning "warty," aptly describing the appearance of Verrucomicrobium spinosum, with its multiple protruding prosthecae.

A remarkable characteristic of Prosthecobacter species is the presence of two genes that exhibit strong similarity to the genes encoding tubulin in eukaryotic cells. Tubulin is the primary protein forming the eukaryotic cytoskeleton. While the bacterial cell division protein FtsZ is also a tubulin homolog, the tubulin-like proteins in Prosthecobacter show greater structural resemblance to eukaryotic tubulin. Despite this similarity, the function of these proteins in Prosthecobacter remains unclear, as no eukaryotic-like cytoskeleton has been observed in these bacteria.