Acidobacteria capsulatum

Classification

Higher order taxa

Bacteria; Fibrobacteres/Acidobacteria group; Acidobacteria; Acidobacteriia; Acidobacteriales; Acidobacteriaceae; Acidobacterium

Species

Acidobacterium capsulatum

NCBI: Taxonomy

Description and significance

Acidobacteria capsulatum (A. capsulatum) is still a relatively new species since its official classification in 1991 but progress has been made towards elucidating the properties and ecological significance of the species. A. capsulatum are gram-negative, acidophilic, heterotrophic, facultatively anaerobic and rod shaped bacteria (1).

A. capsulatum are known to possess flagella that allow motility within the environment (1). The flagella themselves are peritrichous or found all over the surface of the cell. Another characteristic of this organism is the presence of high amounts of exopolysaccharide coating the cells from soil isolates (2). Exopolysaccharide’s function falls into four broads categories: protection, adhesion, an adaption response or cell-cell interactions (3). This contributes to the competitiveness of A. capsulatum, for example, having increased adhesion can allow the bacterium to acquire nutrients more readily from the environment.

Members of this phylum are presumably ubiquitous in soil environments and A. capsulatum could potentially play a major role in the fluxes of carbon,nitrogen and iron across microbial communities due to its metabolic processes and distribution in soils.

Ecology

A. capsulatum, though first isolated from acidic drainage (1), are presumed to be widely distributed in soils as evidenced by the detection of their phylum’s 16s rRNA sequences across a diverse range of environmental samples (4)(Fig 3). Soil samples from Australian forest and Arizona indicated that A. capsulatum was present in the microbial communities. Additionally A. capsulatum also extends its presence to rhizosphere soils, the interface between the plant root and microbial community. Here, members of the Acidobacteria phylum including A. capsulatum were found to have represented a majority of the 16s rRNA sequences found there (5). A. capsulatum then may play a role in the geochemical cycles within these soils.

A. capsulatum prefer to exist in conditions where the soil or the microenvironments within it provide a pH range of 3.0 – 6.0 (6). In addition, they are frequent and sometimes dominant in iron-rich environments such as abandoned mines. This can be attributed to their mode of respiration, iron-reduction, which can play a significant role in iron cycling in these environments.