@article {ISI:000371206300001,
	title = {{A distinct and active bacterial community in cold oxygenated fluids circulating beneath the western flank of the Mid-Atlantic ridge}},
	journal = {SCIENTIFIC REPORTS},
	volume = {6},
	year = {2016},
	month = {mar},
	type = {Article},
	abstract = {The rock-hosted, oceanic crustal aquifer is one of the largest ecosystems on Earth, yet little is known about its indigenous microorganisms. Here we provide the first phylogenetic and functional description of an active microbial community residing in the cold oxic crustal aquifer. Using subseafloor observatories, we recovered crustal fluids and found that the geochemical composition is similar to bottom seawater, as are cell abundances. However, based on relative abundances and functional potential of key bacterial groups, the crustal fluid microbial community is heterogeneous and markedly distinct from seawater. Potential rates of autotrophy and heterotrophy in the crust exceeded those of seawater, especially at elevated temperatures (25 degrees C) and deeper in the crust. Together, these results reveal an active, distinct, and diverse bacterial community engaged in both heterotrophy and autotrophy in the oxygenated crustal aquifer, providing key insight into the role of microbial communities in the ubiquitous cold dark subseafloor biosphere.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {2045-2322},
	doi = {10.1038/srep22541},
	author = {Meyer, Julie L and Jaekel, Ulrike and Tully, Benjamin J and Glazer, Brian T and Wheat, C Geoffrey and Lin, Huei-Ting and Hsieh, Chih-Chiang and Cowen, James P and Hulme, Samuel M and Girguis, Peter R and Huber, Julie A}
}
@article {ISI:000360888000001,
	title = {{Carbon fixation by basalt-hosted microbial communities}},
	journal = {FRONTIERS IN MICROBIOLOGY},
	volume = {6},
	year = {2015},
	month = {sep},
	type = {Article},
	abstract = {Oceanic crust is a massive potential habitat for microbial life on Earth, yet our understanding of this ecosystem is limited due to difficulty in access. In particular, measurements of rates of microbial activity are sparse. We used stable carbon isotope incubations of crustal samples, coupled with functional gene analyses, to examine the potential for carbon fixation on oceanic crust. Both seafloor-exposed and subseafloor basalts were recovered from different mid-ocean ridge and hot spot environments (i.e., the Juan de Fuca Ridge, the Mid-Atlantic Ridge, and the Loihi Seamount) and incubated with C-13-labeled bicarbonate. Seafloor-exposed basalts revealed incorporation of C-13-label into organic matter over time, though the degree of incorporation was heterogeneous. The incorporation of C-13 into biomass was inconclusive in subseafloor basalts. Translating these measurements into potential rates of carbon fixation indicated that 0.1-10 nmol C g(-1) rock d(-1) could be fixed by seafloor-exposed rocks. When scaled to the global production of oceanic crust, this suggests carbon fixation rates of 10(9)-10(12) g C year(-1), which matches earlier predictions based on thermodynamic calculations. Functional gene analyses indicate that the Calvin cycle is likely the dominant biochemical mechanism for carbon fixation in basalt-hosted biofilms, although the reductive acetyl-CoA pathway and reverse TCA cycle likely play some role in net carbon fixation. These results provide empirical evidence for autotrophy in oceanic crust, suggesting that basalt-hosted autotrophy could be a significant contributor of organic matter in this remote and vast environment.},
	keywords = {HOV Alvin (Human Occupied Vehicle), ROV Jason (Remotely Operated Vehicle)},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2015.90400904},
	author = {Orcutt, Beth N and Sylvan, Jason B and Rogers, Daniel R and Delaney, Jennifer and Lee, Raymond W and Girguis, Peter R}
}
@article {ISI:000331005900001,
	title = {{Low temperature geomicrobiology follows host rock composition along a geochemical gradient in Lau Basin}},
	journal = {FRONTIERS IN MICROBIOLOGY},
	volume = {4},
	year = {2013},
	month = {mar},
	type = {Article},
	abstract = {The East Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) comprise a ridge segment in the southwest Pacific Ocean where rapid transitions in the underlying mantle chemistry manifest themselves as gradients in seafloor rock geochemistry. We studied the geology and microbial diversity of three silicate rock samples and three inactive sulfide chimney samples collected, from north to south, at the vent fields Kilo Moana, ABE, Tui Malila, and Mariner. This is the first study of microbial populations on basaltic andesite, which was sampled at Mariner vent field. Silicate rock geochemistry exhibits clear latitudinal trends that are mirrored by changes in bacterial community composition. alpha-proteobacteria, epsilon-proteobacteria, and Bacteroidetes are most common on a silicate collected from Kilo Moana and their proportions decrease linearly on silicates collected further south. Conversely, a silicate from Mariner vent field hosts high proportions of a unique lineage of Chloroflexi unrelated ({\textless}90{\%} sequence similarity) to previously recovered environmental clones or isolates, which decrease at ABE and are absent at Kilo Moana. The exteriors of inactive sulfide structures are dominated by lineages of sulfur oxidizing alpha-proteobacteria, gamma-proteobacteria, and epsilon-proteobacteria, while the interior of one chimney is dominated by putative sulfur-reducing delta-proteobacteria. A comparison of bacterial communities on inactive sulfides from this and previous studies reveals the presence of a clade of uncultured Bacteroidetes exclusive to sulfidic environments, and a high degree of heterogeneity in bacterial community composition from one sulfide structure to another. In light of the heterogeneous nature of bacterial communities observed here and in previous studies of both active and inactive hydrothermal sulfide structures, the presence of numerous niches may be detected on these structures in the future by finer scale sampling and analysis.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2013.00061},
	author = {Sylvan, Jason B and Sia, Tiffany Y and Haddad, Amanda G and Briscoe, Lindsey J and Toner, Brandy M and Girguis, Peter R and Edwards, Katrina J}
}
@article {ISI:000208863500072,
	title = {{Thermodynamics and kinetics of sulfide oxidation by oxygen: a look at inorganically controlled reactions and biologically mediated processes in the environment}},
	journal = {FRONTIERS IN MICROBIOLOGY},
	volume = {2},
	year = {2011},
	type = {Article},
	abstract = {The thermodynamics for the first electron transfer step for sulfide and oxygen indicates that the reaction is unfavorable as unstable superoxide and bisulfide radical ions would need to be produced. However, a two-electron transfer is favorable as stable S(0) and peroxide would be formed, but the partially filled orbitals in oxygen that accept electrons prevent rapid kinetics. Abiotic sulfide oxidation kinetics improve when reduced iron and/or manganese are oxidized by oxygen to form oxidized metals which in turn oxidize sulfide. Biological sulfur oxidation relies on enzymes that have evolved to overcome these kinetic constraints to affect rapid sulfide oxidation. Here we review the available thermodynamic and kinetic data for H2S and HS center dot as well as O-2, reactive oxygen species, nitrate, nitrite, and NOx species. We also present new kinetic data for abiotic sulfide oxidation with oxygen in trace metal clean solutions that constrain abiotic rates of sulfide oxidation in metal free solution and agree with the kinetic and thermodynamic calculations. Moreover, we present experimental data that give insight on rates of chemolithotrophic and photolithotrophic sulfide oxidation in the environment. We demonstrate that both anaerobic photolithotrophic and aerobic chemolithotrophic sulfide oxidation rates are three or more orders of magnitude higher than abiotic rates suggesting that in most environments biotic sulfide oxidation rates will far exceed abiotic rates due to the thermodynamic and kinetic constraints discussed in the first section of the paper. Such data reshape our thinking about the biotic and abiotic contributions to sulfide oxidation in the environment.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2011.00062},
	author = {Luther III, George W and Findlay, Alyssa J and MacDonald, Daniel J and Owings, Shannon M and Hanson, Thomas E and Beinart, Roxanne A and Girguis, Peter R}
}
