@article {1718, title = {Hydrogen and thiosulfate limits for growth of a thermophilic, autotrophic Desulfurobacterium species from a deep-sea hydrothermal vent.}, journal = {Environ Microbiol Rep}, volume = {8}, year = {2016}, month = {2016 Apr}, pages = {196-200}, abstract = {

Hydrothermal fluids (341{\textdegree}C and 19{\textdegree}C) were collected < 1 m apart from a black smoker chimney and a tubeworm mound on the Boardwalk edifice at the Endeavour Segment in the northeastern Pacific Ocean to study anaerobic microbial growth in hydrothermal mineral deposits. Geochemical modelling of mixed vent fluid and seawater suggests the mixture was anoxic above 55{\textdegree}C and that low H2 concentrations (79 μmol kg(-1) in end-member hydrothermal fluid) limit anaerobic hydrogenotrophic growth above this temperature. A thermophilic, hydrogenotrophic sulfur reducer, Desulfurobacterium strain HR11, was isolated from the 19{\textdegree}C fluid raising questions about its H2 -dependent growth kinetics. Strain HR11 grew at 40-77{\textdegree}C (Topt 72-75{\textdegree}C), pH 5-8.5 (pHopt 6-7) and 1-5\% (wt vol(-1) ) NaCl (NaClopt 3-4\%). The highest growth rates occurred when S2 O3 (2-) and S{\textdegree} were reduced to H2 S. Modest growth occurred by NO3 (-) reduction. Monod constants for its growth were Ks of 30 μM for H2 and Ks of 20 μM for S2 O3 (2-) with a μmax of 2.0 h(-1) . The minimum H2 and S2 O3 (2-) concentrations for growth were 3 μM and 5 μM respectively. Possible sources of S2 O3 (2-) and S{\textdegree} are from abiotic dissolved sulfide and pyrite oxidation by O2 .

}, issn = {1758-2229}, doi = {10.1111/1758-2229.12368}, author = {Stewart, Lucy C and Llewellyn, James G and Butterfield, David A and Lilley, Marvin D and Holden, James F} } @article {1708, title = {Hydrogen Production and Enzyme Activities in the Hyperthermophile Thermococcus paralvinellae Grown on Maltose, Tryptone, and Agricultural Waste.}, journal = {Front Microbiol}, volume = {7}, year = {2016}, month = {2016}, pages = {167}, abstract = {

Thermococcus may be an important alternative source of H2 in the hot subseafloor in otherwise low H2 environments such as some hydrothermal vents and oil reservoirs. It may also be useful in industry for rapid agricultural waste treatment and concomitant H2 production. Thermococcus paralvinellae grown at 82{\textdegree}C without sulfur produced up to 5 mmol of H2 L(-1) at rates of 5-36 fmol H2 cell(-1) h(-1) on 0.5\% (wt vol(-1)) maltose, 0.5\% (wt vol(-1)) tryptone, and 0.5\% maltose + 0.05\% tryptone media. Two potentially inhibiting conditions, the presence of 10 mM acetate and low pH (pH 5) in maltose-only medium, did not significantly affect growth or H2 production. Growth rates, H2 production rates, and cell yields based on H2 production were the same as those for Pyrococcus furiosus grown at 95{\textdegree}C on the same media for comparison. Acetate, butyrate, succinate, isovalerate, and formate were also detected as end products. After 100 h, T. paralvinellae produced up to 5 mmol of H2 L(-1) of medium when grown on up to 70\% (vol vol(-1)) waste milk from cows undergoing treatment for mastitis with the bacterial antibiotic Ceftiofur and from untreated cows. The amount of H2 produced by T. paralvinellae increased with increasing waste concentrations, but decreased in P. furiosus cultures supplemented with waste milk above 1\% concentration. All mesophilic bacteria from the waste milk that grew on Luria Bertani, Sheep{\textquoteright}s Blood (selective for Staphylococcus, the typical cause of mastitis), and MacConkey (selective for Gram-negative enteric bacteria) agar plates were killed by heat during incubation at 82{\textdegree}C. Ceftiofur, which is heat labile, was below the detection limit following incubation at 82{\textdegree}C. T. paralvinellae also produced up to 6 mmol of H2 L(-1) of medium when grown on 0.1-10\% (wt vol(-1)) spent brewery grain while P. furiosus produced < 1 mmol of H2 L(-1). Twelve of 13 enzyme activities in T. paralvinellae showed significant (p < 0.05) differences across six different growth conditions; however, methyl viologen-dependent membrane hydrogenase activity remained constant across all media types. The results demonstrate the potential of at least some Thermococcus species to produce H2 if protein and α-glucosides are present as substrates.

}, issn = {1664-302X}, doi = {10.3389/fmicb.2016.00167}, author = {Hensley, Sarah A and Moreira, Emily and Holden, James F} } @article {1206, title = {Hydrogen-limited growth of hyperthermophilic methanogens at deep-sea hydrothermal vents.}, journal = {Proc Natl Acad Sci U S A}, volume = {109}, year = {2012}, month = {2012 Aug 21}, pages = {13674-9}, abstract = {

Microbial productivity at hydrothermal vents is among the highest found anywhere in the deep ocean, but constraints on microbial growth and metabolism at vents are lacking. We used a combination of cultivation, molecular, and geochemical tools to verify pure culture H(2) threshold measurements for hyperthermophilic methanogenesis in low-temperature hydrothermal fluids from Axial Volcano and Endeavour Segment in the northeastern Pacific Ocean. Two Methanocaldococcus strains from Axial and Methanocaldococcus jannaschii showed similar Monod growth kinetics when grown in a bioreactor at varying H(2) concentrations. Their H(2) half-saturation value was 66 μM, and growth ceased below 17-23 μM H(2), 10-fold lower than previously predicted. By comparison, measured H(2) and CH(4) concentrations in fluids suggest that there was generally sufficient H(2) for Methanocaldococcus growth at Axial but not at Endeavour. Fluids from one vent at Axial (Marker 113) had anomalously high CH(4) concentrations and contained various thermal classes of methanogens based on cultivation and mcrA/mrtA analyses. At Endeavour, methanogens were largely undetectable in fluid samples based on cultivation and molecular screens, although abundances of hyperthermophilic heterotrophs were relatively high. Where present, Methanocaldococcus genes were the predominant mcrA/mrtA sequences recovered and comprised \~{}0.2-6\% of the total archaeal community. Field and coculture data suggest that H(2) limitation may be partly ameliorated by H(2) syntrophy with hyperthermophilic heterotrophs. These data support our estimated H(2) threshold for hyperthermophilic methanogenesis at vents and highlight the need for coupled laboratory and field measurements to constrain microbial distribution and biogeochemical impacts in the deep sea.

}, keywords = {Archaea, Biodiversity, Coculture Techniques, DNA, Ribosomal, Ecosystem, Gases, Geography, Hydrogen, Hydrothermal Vents, Kinetics, Methane, Molecular Sequence Data, Temperature, Time Factors, Water Microbiology}, issn = {1091-6490}, doi = {10.1073/pnas.1206632109}, author = {Ver Eecke, Helene C and Butterfield, David A and Huber, Julie A and Lilley, Marvin D and Olson, Eric J and Roe, Kevin K and Evans, Leigh J and Merkel, Alexandr Y and Cantin, Holly V and Holden, James F} }