Candidatus Solibacter usitatus
Classification
Domain (Bacteria), Phylum (Acidobacteria), Class (Solibacteres), Order (Solibacterales), Family (Solibacteraceae), Genus (Candidatus Solibacter)
Species
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NCBI: Taxonomy |
Genus species (Candidatus Solibacter usitatus)
Description and Significance
Candidatus Soilbacter usitaus was initially isolated from rotationally grazed pasture of perennial ryegrass and white clover in Victoria, Australia (1). This species is common and very prevalent in its environment. It was found to be the most common organism in a study conducted in 2012 analyzing bacterial composition of Antarctic soil (2).
This species has been difficult to culture in the lab. Filaments have been observed microscopically in soils, but it was found to form clusters in liquid culture (3). In nature, this species produces a biofilm that acts as an ecosystem engineer in soil. It does this by acting as a medium between soil particles to reduce moisture and nutrient fluxuations as well as aid in resource acquisition, which serves to aid survival under environmental stress conditions (4).
This species has an exceptionally large genome and is theorized to engage in horizontal gene transfer which contributes to this species ability to persist in its environment. It is theorized to be capable breaking down plant compounds for metabolism, and to participate in respiratory denitrification which lends to the creation of heterogeneous nutrient concentrations in its environment (4).
Genome Structure
Based on the sequenced genome, Candidatus Soilbacter usitaus was found to have a genome 9.9 Mb long (5), which is about twice the size of other closely related Acidiobacteria found to inhabit soil (4). Horizontal gene transfer is hypothesized to account for how this species acquired its unusual genome size (4), and implies biological and ecological strains upon the living organism to participate in this type of gene transfer (5). It is theorized that the amount of mobile elements encoded in a genome correlate with the historical frequency of horizontal gene transfer events. This is significant because mobile elements are theorized to contribute toward genome plasticity and evolution over time, which could provide a competitive advantage to this species and enable it to exploit various environmental resources (6). Genomic sequencing found a large number of genes encoding for carbohydrate transport and metabolism; more than “the human genome and about three times as many as Saccharomyces cerevisiae” (8). These genes were also found to have high sequence similarity with fungal homologs which further suggests an ancestral horizontal gene transfer that has been unreported among other organisms producing glycoside hydrolase enzymes (4). Whole genome sequencing also found genes encoding for candidate cellulases of glycoside hydrolases, suggesting Candidatus Solibacter usitatus is capable of degrading cellulose substrates and implies the genome is also encoded with other enzymes capable of degrading plant compounds (4). This analysis also suggests it has the flexibility to metabolize carbon as a mixotroph because it contains genes encoding for carbon monoxide dehydrogenase (7). Since oxidation of carbon monoxide has been prevalently documented among other major groups of soil organisms (7), it is hypothesized that this along with the ability to degrade complex polymers associated with vegetation, occur as a survival mechanism in environments with low carbon concentration (4).
The genetic potential for nitrate reductase was observed though no evidence for nitrogen fixation has been demonstrated (4). The potential for respiratory denitrification is significant because it leads to heterogeneous pockets in soil causing spatial variable in nutrient concentrations across a landscape. While Candidatus Solibacter usitatus is not thought to contain genes for iron permease, which is involved in iron uptake (9), it has sequences with domain structures similar to those used in other species. Gene sequence libraries document the 16S rRNA from iron-rich mine environments to be frequently dominated by Acidobacteria (10, 11, 12). This suggests possible involvement with iron (II) uptake and is hypothesized to be a valuable role in iron redox reactions (4).
Cell Structure, Metabolism and Life Cycle
Interesting features of cell structure; how it gains energy; what important molecules it produces.
Ecology and Pathogenesis
Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
References
Author
Page authored by _____, student of Prof. Jay Lennon at IndianaUniversity.
