Diversity of As metabolism functional genes in Pb-Zn mine tailings

Abstract Microbial activities impact arsenic (As) transformation in mine tailings substantially, yet little is understood on the functional diversity of As metabolism genes. This study explored this issue using a metagenomic approach coupled by a local BLASTN procedure established in our recent studies. An assembled metagenome, recovered from hypersaline and sulfidic mine tailings, was screened for As metabolism genes aioA, arrA, arsC and arsM. This was done using a local BLASTN procedure against databases of the As metabolism genes built in this study. Putative As metabolism genes detected in the assembled metagenome included 11 arsM, 20 arsC and 1 arrA full-length sequences. Together with the rRNA-based phylogenetic profiling results, a picture depicting microbial As cycling in the tailings to the genus level was obtained. It was found that most of the dominant genera in the tailings potentially harboured the genes for As reduction and/or methylation. In particular, a typical pyrite-eater present in the tailings, Thioalkalivibrio sp., was found to harbour not only arsC and arsM, but also arrA. These results highlight the unexpected diversity of As metabolism genes in the tailings, especially considering the extremely low species diversity therein. The microbial As cycling picture established here has potential use for guiding the purposeful manipulation of As biogeochemistry in the tailings.