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An extensive culture-dependent and –independent study was conducted to identify microorganisms contributing to the biogeochemical cycling of manganese (Mn) in Ashumet Pond, a freshwater pond in Massachusetts currently undergoing remediation. A variety of bacteria (including Gamma-, Beta-, and Alpha-proteobacteria, Firmicutes, and Bacteroides) and Ascoymete fungi were isolated from the pond that promote Mn(II) oxidation and subsequent formation of Mn(III/IV) oxide minerals. Targeted-amplicon pyrosequencing of the bacterial and fungal communities associated with Mn oxide-encrusted samples show a highly diverse microbial community, of which the cultured phylotypes represent a minor proportion. This suggests a larger community, not identified through culturing, contributes to Mn oxide formation within the Pond.

The upper Tennessee River Basin contains the highest density of our nation's caves; yet, little is known regarding speleogenesis or Fe and Mn biomineralization in these predominantly epigenic systems. Mn:Fe ratios of Mn and Fe oxide-rich biofilms, coatings, and mineral crusts that were abundant in several different caves ranged from ca. 0.1 to 1.0 as measured using ICP-OES. At sites where the Mn:Fe ratio approached 1.0 this represented an order of magnitude increase above the bulk bedrock ratio, suggesting that biomineralization processes play an important role in the formation of these cave ferromanganese deposits. Estimates of total bacterial SSU rRNA genes in ferromanganese biofilms, coatings, and crusts measured approximately 7×107–9×109 cells/g wet weight sample. A SSU-rRNA based molecular survey of biofilm material revealed that 21% of the 34 recovered dominant (non-singleton) OTUs were closely related to known metal-oxidizing bacteria or clones isolated from oxidized metal deposits. Several differe...

Microbial communities inhabiting subseafloor ocean crust were analyzed using culture-dependent and -independent techniques of volcanic basement drill-cores from various locations in the Pacific Ocean. Our results suggest that a low-diversity community of bacteria belonging to the Betaproteobacteria, Alphaproteobacteria, and Bacteroidetes exists in this rocky habitat. Drilling-related contamination was observed, however, identification of these phylotypes was (and will continue to be) beneficial for distinguishing indigenous from contamination-related communities. Due to difficulties in accessing the subseafloor crustal environment, this study further highlights the necessity for innovative approaches in future drilling-based microbiological studies conducted in ocean crust.