arsenite-oxidizing bacteria in activated sludge Raw sequence reads. arsenite-oxidizing bacteria in activated sludge

Biological As(III) oxidation is a key step to remove the toxic As(III) from contaminated water. The capability of As(III) oxidation and the microbial community responsible for this process in wastewater treatment facilities, however, is not well documented. In this study, two groups of lab-scale bioreactors were operated to investigate the capability of biological As(III) oxidation by treating As(III)-containing wastewater. It is indicated that As(III) oxidation could occur under anoxic and oxic conditions. The kinetic model suggested that the rate of oxic As(III) oxidation was higher than anoxic condition. Microcosm experiments further indicated that the biological As(III) oxidation process could be driven by microorganisms using the nitrate or oxygen as the available electron acceptors, suggesting the potentials of this process in wastewater treatment facilities. In addition, DNA based stable isotope probing (DNA-SIP) was performed to identify the putative chemoautotrophic As(III)-oxidizing bacteria (AOBs) inhabiting the activated sludge. Bacteria associated with Hydrogenophaga were identified as an aerobic AOB,while Thiobacillus were identified as a nitrate-dependent AOB. Moreover, metagenomic binning reconstructed a number of high-quality metagenome-assembled genomes (MAGs) associated with putative AOBs. Function genes encoding the As resistance, As(III) oxidation, denitrification, and carbon fixation were identified in these AOBs-associated MAGs, suggesting their potentials of anoxic and/or oxic chemoautotrophic As(III) oxidation. In addition, the detection of genes encoding the secondary metabolite biosynthesis and extracellular polymeric substances metabolisms in these MAGs may facilitate the thrive of putative AOBs and enhance their capability for As(III) oxidation.