@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 {1202, title = {Growth kinetics and energetics of a deep-sea hyperthermophilic methanogen under varying environmental conditions.}, journal = {Environ Microbiol Rep}, volume = {5}, year = {2013}, month = {2013 Oct}, pages = {665-71}, abstract = {

A hyperthermophilic deep-sea methanogen, Methanocaldococcus strain JH146, was isolated from 26{\textdegree}C hydrothermal fluid at Axial Volcano to model high temperature methanogenesis in the subseafloor. Emphasis was placed on defining growth kinetics, cell yields and growth energy demand (GE) across a range of conditions. The organism uses H2 and CO2 as its sole carbon and energy sources. At various temperatures, pHs, and chlorinities, its growth rates and cell yields co-varied while GE remained uniform at 1.69 {\texttimes} 10(-11) J cell(-1)s(-1) {\textpm} 0.68 {\texttimes} 10(-11) J cell(-1)s(-1) (s.d., n = 23). An exception was at superoptimal growth temperatures where GE increased to 7.25 {\texttimes} 10(-11) J cell(-1)s(-1) presumably due to heat shock. GE also increased from 5.1 {\texttimes} 10(-12) J cell(-1)s(-1) to 7.61 {\texttimes} 10(-11) J cell(-1)s(-1) as NH4 (+) concentrations decreased from 9.4 mM to 0.14 mM. JH146 did not fix N2 or assimilate NO3 (-), lacked the N2-fixing (cluster II) nifH gene, and became nitrogen limited below 0.14 mM NH4Cl. Nitrogen availability may impact growth in situ since ammonia concentrations at Axial Volcano are < 18 μM. Our approach contributes to refining bioenergetic and carbon flux models for methanogens and other organisms in hydrothermal vents and other environments.

}, issn = {1758-2229}, doi = {10.1111/1758-2229.12065}, author = {Ver Eecke, Helene C and Akerman, Nancy H and Huber, Julie A and Butterfield, David A 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} }