PNNL

Abstract

A microbial census on the deep biosphere (1.34 km depth) microbial communities was performed in two soil samples collected from the Ross and number 6 Winze sites of the former Homestake gold mine, Lead, South Dakota using high-density 16S microarrays (PhyloChip). Mineralogical characterization of soil samples was carried out using X-ray diffraction, X-ray photoelectron, and Mössbauer spectroscopic techniques which demonstrated the presence of silicates and iron minerals (phyllosilicates and clays) in both samples. Microarray data revealed extensive bacterial diversity in soils and detected the largest number of taxa in Proteobacteria phylum followed by Firmicutes and Actinobacteria. The archael communities in the deep gold mine environments were less diverse and belonged to phyla Euryarchaeota and Crenarchaeota. Both the samples showed remarkable amount of similar microbial communities (1360 common OTUs) despite of distinct geochemical characteristics. A total of 57 phylotypes could not be classified even at phylum level representing a hitherto unidentified diversity in deep biosphere. PhyloChip data also suggested considerable metabolic diversity in deep biosphere by capturing several physiological groups of bacteria such as sulfur-oxidizer, ammonia-oxidizers, iron-oxidizers, methane-oxidizers, and sulfate-reducers in both samples. Application of high-density microarrays revealed the vast prokaryotic diversity ever reported from deep subsurface habitat of gold mines.