Assessment of abundance and diversity of exoelectrogenic bacteria in soil under different land use types

Soil exoelectrogenic bacteria have been found to perform various functions. However, little is known about whether exoelectrogenic bacteria are widely distributed in soil and which physico-chemical properties of soil significantly affect their distribution? To address the research questions, 37 soil samples covering six land use types, including arid farmland soils, woodland soils, grassland soils, paddy soils, lakeshore soils, and coastal soils were collected. DNA was extracted from all the samples for quantitative PCR and high throughput sequencing of the 16S rRNA gene. The sequencing result showed a total of 16 exoelectrogenic bacteria-associated genera from different soils. The total abundance of these genera varied from 1.14 × 108 copies g−1 in a farmland soil to 7.89 × 109 copies g−1 in a coastal soil, accounting for 0.26% to 7.70% of the total bacteria. Among the 16 genera, Bacillus was dominant in the arid land soils, including the farmland, woodland, and grassland soils. The coastal soils were dominated by Desulfobulbus whereas the paddy and lakeshore soils were characterized by abundant Geobacter. Principal component analysis showed a distinct separation of the exoelectrogenic bacterial community between the arid land (farmland, woodland, and grassland soils), freshwater wetland (paddy and lakeshore soils), and coastal soils. Redundancy analysis revealed that the water content, electrical conductivity and concentrations of total sulphur and amorphous Fe in the soil were significant factors driving the community structure and abundance of exoelectrogenic bacteria-associated genera. Our results should help in better understanding of the exoelectrogenic bacteria-mediated functions in soil, which might contribute to the biogeochemical cycling of a large number of organic and inorganic materials.