The Duluth Complex in Northeastern Minnesota is one of the largest undeveloped copper nickel deposits on Earth. The ores occur in basal sulfide units that contain pyrrhotite, chalcopyrite, cubanite, pentlandite, and other Cu and Ni-bearing sulfide minerals. Little is known, however, about the microbial communities and processes that could impact sulfide mineral oxidation in the Duluth Complex. In earlier work, rRNA gene and transcript sequencing of long-term leaching experiments revealed that many of the abundant taxa associated with Duluth Complex ores and waste rock are from clades that are only known from environmental samples and are not typically associated with mine waste. We therefore applied metagenomics to probe the metabolic capabilities of uncultivated populations from the weathered Duluth Complex materials. We used de novo assembly and tetranucleotide binning to reconstruct mostly-complete genomes from several of the dominant populations, including Sulfuriferula spp., Meiothermus spp., an unnamed betaproteobacterium, and multiple organisms from class Ktedonobacteria in the Chloroflexi. Sulfuriferula, which represent up to 30% of the rock-associated communities, are autotrophs that use the SQR system and a partial SOX system to oxidize reduced inorganic sulfur compounds. We also compared Sulfuriferula bins from the metagenomes against a complete genome sequence of a Sulfuriferula isolate that was reconstructed using long-read sequencing. We will report culture-based, microscopic, genomic and metagenomic insights into the metabolic capabilities of Sulfuriferula spp. and other populations from the weathering experiments, and discuss how these organisms influence sulfide mineral oxidation and other important chemical transformations in Duluth Complex waste rock.

Metagenomic and genomic characterization of novel organisms associated with sulfide mineral leaching in ore and waste rock from the Duluth Complex, Minnesota

253rd National Meeting (2017)

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