Manganese-reducing Pseudomonas fluorescens-group bacteria control arsenic mobility in gold mining-contaminated groundwater

Abstract

Previous studies show the importance of iron- and arsenate-reducing bacteria in mobilizing arsenic in groundwater. Here the authors present experimental evidence of arsenic mobilization in connection with bacterially mediated manganese reduction in groundwater affected by mining activities. Manganese-reducing Pseudomonas species were enriched, isolated and identified by 16S rRNA gene phylogeny from groundwater containing high co-dissolved arsenic (as AsIII) and manganese. Enrichment cultures dissolved synthetic birnessite and hausmannite efficiently, but Mn reduction by isolates was reduced at the upper range of environmental levels of dissolved AsIII. Results suggest either a self-limiting release of arsenic coupled to bacterial manganese reduction, in the absence of other electron donors like sulfide, or increased arsenic resistance conferred to Mn-reducing bacteria in consortia.