細菌門：ヴェルコミクロビア

Verrucomicrobiota comprises at least four characterized orders, with most species in the order Verrucomicrobiales. Members are aerobic or facultatively aerobic bacteria distributed across freshwater, marine habitats, forest soils, and agricultural lands. A distinctive feature is their possession of cytoplasmic extensions called prosthecae, supported by peptidoglycan in cell walls, distinguishing them from bacterial phylum planctomycetes.

Verrucomicrobium and Prosthecobacter undergo symmetrical cell division, resulting in both mother and daughter cells possessing prosthecae at division time. This contrasts with Caulobacter, which develops a single prostheca and releases flagellated swarmer cells lacking prosthecae. The name Verrucomicrobium derives from Greek meaning warty, describing their multiple protruding prosthecae.

Verrucomicrobiota species contribute significantly to carbon cycling through diverse metabolic pathways. Many species ferment sugars for energy, while aerobic methanotrophs like Methylacidiphilum oxidize methane. Additionally, some Verrucomicrobiota establish symbiotic relationships with protists, expanding their ecological roles and nutrient cycling capabilities across diverse habitats.

Prosthecae are membrane-bound cytoplasmic extensions characteristic of Verrucomicrobiota. These appendages are supported by peptidoglycan in their cell walls, distinguishing them from similar structures in other bacteria. The genera Verrucomicrobium and Prosthecobacter produce multiple prosthecae on each cell, giving them their distinctive warty appearance.

Prosthecobacter species possess two genes exhibiting strong similarity to eukaryotic tubulin genes, the primary protein forming eukaryotic cytoskeletons. These bacterial tubulin-like proteins show greater structural resemblance to eukaryotic tubulin than the bacterial FtsZ protein. However, their function remains unclear since no eukaryotic-like cytoskeleton has been observed in these bacteria.

Verrucomicrobiota is classified into four orders, with most species in the order Verrucomicrobiales. Classification relies on molecular and morphological characteristics examined through methods of classification and identification. Understanding their classification helps contextualize their role within microbial diversity and their relationships to other bacterial groups.

Both Verrucomicrobiota and Planctomycetes possess membrane-bound intracellular structures. However, Verrucomicrobiota's distinctive feature is cytoplasmic extensions called prosthecae supported by peptidoglycan in cell walls. This structural difference sets Verrucomicrobiota apart and reflects their unique evolutionary adaptations within bacterial diversity and ecological niches.