MICROBIOLOGICAL ANTIMONY CYCLING IN A DIVERSITY OF ENVIRONMENTAL SETTINGS

Microorganisms directly control the redox speciation and environmental behavior of toxic metalloids (e.g., As, Se, Te). Bacterial reduction and oxidation of metalloids is achieved through enzymatically-catalyzed reactions coupled to metabolic processes or, alternately, to detoxification mechanisms to facilitate extrusion of the metalloid from the cellular interior. Microbiological transformations of As include As(V) reduction to As(III) as a terminal electron acceptor for anaerobic respiration, as well as chemoautotrophic As(III) oxidation. These As-based metabolisms have been elicited in phylogenetically diverse prokaryotes cultured from a wide range of mesophilic and extemophilic environments (freshwater streams, aquifers, soda lakes, and hot springs). Sb is a toxic metalloid of emerging global concern that co-occurs with As in group 15 of the periodic table and shares many similar chemical and toxicological properties. In recent years our emerging picture of the geomicrobiological Sb cycle has revealed distinct similarities to that of As. A rapidly growing number of studies have reported the isolation of Sb(III)-oxidizing bacterial strains from Sb-contaminated freshwater settings and Abin and Hollibaugh (2014) recently reported that a Firmicutes isolate from hypersaline and alkaline Mono Lake grew by reducing Sb(V) as a terminal electron acceptor for heterotrophic respiration. However, the relative ubiquity of Sb-cycling bacteria in diverse environments or in environments that are not heavily impacted by particularly elevated Sb concentrations has not been explored. Here we report Sb(V)-dependent heterotrophic respiration in phylogenetically diverse bacterial strains isolated from 1) a Sb- and As-impacted (Sb: >1000 mg/kg) mine tailings site; 2) a hydrothermally influenced drainage in Eastern Oregon, and 3) Mono Lake sediment. In addition, Sb(III)-dependent chemolithoautotrophic growth was isolated from a roadside soil in upstate New York that was contaminated with only very low (>10 mg/kg) concentrations of Sb derived from traffic. Our results suggest that capacity for microbiological reduction and oxidation of Sb is widespread in phylogenetically diverse bacteria and ubiquitous in a wide range of environments.