@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:000348807500001,
	title = {{Activity and phylogenetic diversity of sulfate-reducing microorganisms in low-temperature subsurface fluids within the upper oceanic crust}},
	journal = {FRONTIERS IN MICROBIOLOGY},
	volume = {5},
	year = {2015},
	month = {jan},
	type = {Article},
	abstract = {The basaltic ocean crust is the largest aquifer system on Earth, yet the rates of biological activity in this environment are unknown. Low-temperature ({\textless}100 degrees C) fluid samples were investigated from two borehole observatories in the Juan de Fuca Ridge (JFR) flank, representing a range of upper oceanic basement thermal and geochemical properties. Microbial sulfate reduction rates (SRR) were measured in laboratory incubations with S-35-sulfate over a range of temperatures and the identity of the corresponding sulfate-reducing microorganisms (SRM) was studied by analyzing the sequence diversity of the functional marker dissimilatory (bi)sulfite reductase (dsrAB) gene. We found that microbial sulfate reduction was limited by the decreasing availability of organic electron donors in higher temperature, more altered fluids. Thermodynamic calculations indicate energetic constraints for metabolism, which together with relatively higher cell-specific SRR reveal increased maintenance requirements, consistent with novel species-level dsrAB phylotypes of thermophilic SRM. Our estimates suggest that microbially-mediated sulfate reduction may account for the removal of organic matter in fluids within the upper oceanic crust and underscore the potential quantitative impact of microbial processes in deep subsurface marine crustal fluids on marine and global biogeochemical carbon cycling.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2014.00748},
	author = {Robador, Alberto and Jungbluth, Sean P and LaRowe, Douglas E and Bowers, Robert M and Rappe, Michael S and Amend, Jan P and Cowen, James P}
}
@article {ISI:000343625500006,
	title = {{Dissolved hydrogen and methane in the oceanic basaltic biosphere}},
	journal = {EARTH AND PLANETARY SCIENCE LETTERS},
	volume = {405},
	year = {2014},
	month = {nov},
	pages = {62{\textendash}73},
	type = {Article},
	abstract = {The oceanic basaltic crust is the largest aquifer on Earth and has the potential to harbor substantial subsurface microbial ecosystems, which hitherto remains largely uncharacterized and is analogous to extraterrestrial subsurface habitats. Within the sediment-buried 3.5 Myr old basaltic crust of the eastern Juan de Fuca Ridge flank, the circulating basement fluids have moderate temperature (similar to 65 degrees C) and low to undetectable dissolved oxygen and nitrate concentrations. Sulfate, present in high concentrations, is therefore expected to serve as the major electron acceptor in this subsurface environment. This study focused on the availability and potential sources of two important electron donors, methane (CH4) and hydrogen (H-2), for the subseafloor biosphere. High integrity basement fluids were collected via fluid delivery lines associated with Integrated Ocean Drilling Program (IODP) Circulation Obviation Retrofit Kits (CORKs) that extend from basement depths to outlet ports at the seafloor. Two new CORKs installed during IODP 327 in 2010, 1362A and 1362B, were sampled in 2011 and 2013. The two CORKs are superior than earlier style CORKs in that they are equipped with coated casing and polytetrafluoroethylene fluid delivery lines, reducing the interaction between casing materials with the environment. Additional samples were collected from an earlier style CORK at Borehole 1301A. The basement fluids are enriched in H-2 (0.05-1.8 mu mol/kg), suggesting that the ocean basaltic aquifer can support H-2-driven metabolism. The basement fluids also contain significant amount of CH4 (5-32 mu mol/kg), revealing CH4 as an available substrate for subseafloor basaltic habitats. The delta C-13 values of CH4 from the three boreholes ranged from -22.5 to -58 parts per thousand, while the delta H-2 values ranged from 316 to 57 parts per thousand. The isotopic compositions of CH4 and the molecular compositions of hydrocarbons suggest that CH4 in the basement fluids is of both biogenic and abiotic origins, varying among sites and sampling times. The delta H-2 values of CH4 in CORK 1301A fluid samples are much more positive than found in all other marine environments investigated to date and are best explained by the partial microbial oxidation of biogenic CH4. In conclusion, our study shows that CH4 and H-2 are persistently available to fuel the deep biosphere and that CH4 is both produced and potentially consumed by microorganisms in the oceanic basement. (C) 2014 Elsevier B.V. All rights reserved.},
	keywords = {ROV Jason (Remotely Operated Vehicle)},
	issn = {0012-821X},
	doi = {10.1016/j.epsl.2014.07.037},
	author = {Lin, Huei-Ting and Cowen, James P and Olson, Eric J and Lilley, Marvin D and Jungbluth, Sean P and Wilson, Samuel T and Rappe, Michael S}
}
@article {ISI:000313236000014,
	title = {{Microbial diversity within basement fluids of the sediment-buried Juan de Fuca Ridge flank}},
	journal = {ISME JOURNAL},
	volume = {7},
	number = {1},
	year = {2013},
	month = {jan},
	pages = {161{\textendash}172},
	type = {Article},
	abstract = {Despite its immense size, logistical and methodological constraints have largely limited microbiological investigations of the subseafloor basement biosphere. In this study, a unique sampling system was used to collect fluids from the subseafloor basaltic crust via a Circulation Obviation Retrofit Kit (CORK) observatory at Integrated Ocean Drilling Program borehole 1301A, located at a depth of 2667 m in the Pacific Ocean on the eastern flank of the Juan de Fuca Ridge. Here, a fluid delivery line directly accesses a 3.5 million years old basalt-hosted basement aquifer, overlaid by 262 m of sediment, which serves as a barrier to direct exchange with bottom seawater. At an average of 1.2 x 10(4) cells ml(-1), microorganisms in borehole fluids were nearly an order of magnitude less abundant than in surrounding bottom seawater. Ribosomal RNA genes were characterized from basement fluids, providing the first snapshots of microbial community structure using a high-integrity fluid delivery line. Interestingly, microbial communities retrieved from different CORKs (1026B and 1301A) nearly a decade apart shared major community members, consistent with hydrogeological connectivity. However, over three sampling years, the dominant gene clone lineage changed from relatives of Candidatus Desulforudis audaxviator within the bacterial phylum Firmicutes in 2008 to the Miscellaneous Crenarchaeotic Group in 2009 and a lineage within the JTB35 group of Gammaproteobacteria in 2010, and statistically significant variation in microbial community structure was observed. The enumeration of different phylogenetic groups of cells within borehole 1301A fluids supported our observation that the deep subsurface microbial community was temporally dynamic. The ISME Journal (2013) 7, 161-172; doi:10.1038/ismej.2012.73; published online 12 July 2012},
	keywords = {HOV Alvin (Human Occupied Vehicle), ROV Jason (Remotely Operated Vehicle)},
	issn = {1751-7362},
	doi = {10.1038/ismej.2012.73},
	author = {Jungbluth, Sean P and Grote, Jana and Lin, Huei-Ting and Cowen, James P and Rappe, Michael S}
}
