Detection of arsenite-oxidizing bacteria in groundwater from a gold mine under different geochemical environments

Abstract

Millions of people around the world potentially expose to arsenic (As) contaminated groundwater. Besides, the dominant form of As in groundwater is arsenite (As+3) and is more toxic than arsenate (As+5). This study integrated the microbial investigation, geochemical modeling, and multivariate statistical analysis to investigate the arsenite-oxidizing bacteria community from As-contaminated groundwater and its environmental influencing factors in order to understand and further develop the in-situ arsenic bioremediation technology. Microbial investigation was focusing on the detection and identification of native arsenite-oxidizing bacterial community using PCR-DGGE, cloning and sequencing of arsenite oxidase (aoxB) gene amplicons. Nine groundwater samples were collected from the gold mine and residential areas. Surface water and soil samples were also collected from upstream, within, and downstream of the gold mining area and then were compared each other. The results showed that the majority of arsenite-oxidizing bacteria was related to α-, β-proteobacteria-like clusters in which the environmental media divided them into separated clusters. Many of groundwater clones revealed affiliated to the member of β-proteobacteria class where it was contributed by Hydrogenophaga, Burkholderia, Alcaligenes, Variovorax, Thiomonas, and Cupriavidus genera. This finding implied that these native arsenite-oxidizing bacteria might play a key role in controlling an As geochemistry in As-contaminated groundwater. Moreover, PHREEQC geochemical modeling of As and multivariate statistical analysis revealed that As presented as As5+ in most groundwater samples. However, the speciations seemed to be not driven by the arsenite-oxidizing bacterial community, but geochemical charateristics of groundwater, which were pH, ORP, and DO, influence on the shape their communities significantly, while As, and Fe concentrations play a minor role.