O12-06 : Diversity of microbial arsenic transformation pathways associated with arsenic cycling in the environment
1CMES, Ehime Univ.
Arsenic (As) is a naturally occurring toxic element widely distributed in nature. Despite its toxicity, microorganisms have developed mechanisms to tolerate As and utilize the element for respiratory metabolism. Although various microorganisms have been identified to catalyze As transformations, we have just began to unveil the full diversity of microbial processes associated with As cycling in the environment. To gain insight into microbial roles in the geochemical dynamics of As, the combined geochemical, physiological, and omics approaches were applied to examine As-impacted environments. The genes coding for arsenite oxidase (aio), which catalyzes the oxidation of arsenite coupled to O2 reduction, have been recovered from geothermal habitats as well as the mine tailing soils. In contrast, from the As impacted lake sediments and soils, diverse sequences of anaerobic arsenite oxidase (arx) and arsenate respiratory reductase (arr) genes were detected, while aio gene transcripts were only detectable upon exposure to As. Successful cultivation of various As-transforming bacteria confirmed the microbial attribute in As redox metabolisms. Our results showed that As redox metabolisms are widespread within phylogenetically and physiologically diverse bacteria, and the diverse As transformation pathways are associated with geographically and geochemically distinct environments.