Arsenic speciation, the abundance of arsenite-oxidizing bacteria and microbial community structures in groundwater, surface water, and soil from a gold mine

Abstract

The arsenic speciation, the abundance of arsenite-oxidizing bacteria, and microbial community structures in the groundwater, surface water, and soil from a gold mining area were explored using the PHREEQC model, cloning-ddPCR of the <i>aioA</i> gene, and high-throughput sequencing of the 16S rRNA gene, respectively. The analysis of the <i>aioA</i> gene showed that arsenite-oxidizing bacteria retrieved from groundwater, surface water, and soil were associated with <i>Alphaproteobacteria</i>, <i>Betaproteobacteria</i>, and <i>Gammaproteobacteria</i>. In groundwaters from the mining area, there were relatively high ratios of <i>aioA</i>/total 16S rRNA gene copies and the dominance of As⁵⁺, which suggested the presence and activity of arsenite-oxidizing bacteria. Metagenomic analysis revealed that the majority of the soil and surface water microbiomes were <i>Proteobacteria</i>, <i>Actinobacteria</i>, <i>Bacteroidetes</i>, and <i>Chloroflexi</i>, whereas the groundwater microbiomes were dominated exclusively by <i>Betaproteobacteria</i> and <i>Alphaproteobacteria</i>. Geochemical factors influencing the microbial structure in the groundwater were As, residence time, and groundwater flowrate, while those showing a positive correlation to the microbial structure in the surface water were TOC, ORP, and DO. This study provides insights into the groundwater, surface water, and soil microbiomes from a gold mine and expands the current understanding of the diversity and abundance of arsenite-oxidizing bacteria, playing a vital role in global As cycling.