TY - JOUR A1 - Cockell, Charles S. A1 - Voytek, Mary A. A1 - Gronstal, Aaron L. A1 - Finster, Kai A1 - Kirshtein, Julie D. A1 - Howard, Kieren A1 - Reitner, Joachim A1 - Gohn, Gregory S. A1 - Sanford, Ward E. A1 - Horton, J. Wright A1 - Kallmeyer, Jens A1 - Kelly, Laura A1 - Powars, David S. T1 - Impact disruption and recovery of the deep subsurface biosphere JF - Astrobiology N2 - Although a large fraction of the world's biomass resides in the subsurface, there has been no study of the effects of catastrophic disturbance on the deep biosphere and the rate of its subsequent recovery. We carried out an investigation of the microbiology of a 1.76 km drill core obtained from the similar to 35 million-year-old Chesapeake Bay impact structure, USA, with robust contamination control. Microbial enumerations displayed a logarithmic downward decline, but the different gradient, when compared to previously studied sites, and the scatter of the data are consistent with a rnicrobiota influenced by the geological disturbances caused by the impact. Microbial abundance is low in buried crater-fill, ocean-resurge, and avalanche deposits despite the presence of redox couples for growth. Coupled with the low hydraulic conductivity, the data suggest the microbial community has not yet recovered from the impact similar to 35 million years ago. Microbial enumerations, molecular analysis of microbial enrichment cultures, and geochemical analysis showed recolonization of a deep region of impact-fractured rock that was heated to above the upper temperature limit for life at the time of impact. These results show how, by fracturing subsurface rocks, impacts can extend the depth of the biosphere. This phenomenon would have provided deep refugia for life on the more heavily bombarded early Earth, and it shows that the deeply fractured regions of impact craters are promising targets to study the past and present habitability of Mars. KW - Asteroid KW - Impacts KW - Subsurface biosphere KW - Subterranean environment KW - Geobiology Y1 - 2012 U6 - https://doi.org/10.1089/ast.2011.0722 SN - 1531-1074 VL - 12 IS - 3 SP - 231 EP - 246 PB - Liebert CY - New Rochelle ER - TY - JOUR A1 - Roy, Hans A1 - Kallmeyer, Jens A1 - Adhikari, Rishi Ram A1 - Pockalny, Robert A1 - Jorgensen, Bo Barker A1 - D'Hondt, Steven T1 - Aerobic microbial respiration in 86-million-year-old deep-sea red clay JF - Science N2 - Microbial communities can subsist at depth in marine sediments without fresh supply of organic matter for millions of years. At threshold sedimentation rates of 1 millimeter per 1000 years, the low rates of microbial community metabolism in the North Pacific Gyre allow sediments to remain oxygenated tens of meters below the sea floor. We found that the oxygen respiration rates dropped from 10 micromoles of O-2 liter(-1) year(-1) near the sediment-water interface to 0.001 micromoles of O-2 liter(-1) year(-1) at 30-meter depth within 86 million-year-old sediment. The cell-specific respiration rate decreased with depth but stabilized at around 10(-3) femtomoles of O-2 cell(-1) day(-1) 10 meters below the seafloor. This result indicated that the community size is controlled by the rate of carbon oxidation and thereby by the low available energy flux. Y1 - 2012 U6 - https://doi.org/10.1126/science.1219424 SN - 0036-8075 VL - 336 IS - 6083 SP - 922 EP - 925 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Ciobanu, M. -C. A1 - Rabineau, M. A1 - Droz, L. A1 - Revillon, S. A1 - Ghiglione, J. -F. A1 - Dennielou, B. A1 - Jorry, S. -J. A1 - Kallmeyer, Jens A1 - Etoubleau, J. A1 - Pignet, P. A1 - Crassous, P. A1 - Vandenabeele-Trambouze, O. A1 - Laugier, J. A1 - Guegan, M. A1 - Godfroy, A. A1 - Alain, K. T1 - Sedimentological imprint on subseafloor microbial communities in Western Mediterranean Sea Quaternary sediments JF - Biogeosciences N2 - An interdisciplinary study was conducted to evaluate the relationship between geological and paleoenvironmental parameters and the bacterial and archaeal community structure of two contrasting subseafloor sites in the Western Mediterranean Sea (Ligurian Sea and Gulf of Lion). Both depositional environments in this area are well-documented from paleoclimatic and paleooceanographic point of views. Available data sets allowed us to calibrate the investigated cores with reference and dated cores previously collected in the same area, and notably correlated to Quaternary climate variations. DNA-based fingerprints showed that the archaeal diversity was composed by one group, Miscellaneous Crenarchaeotic Group (MCG), within the Gulf of Lion sediments and of nine different lineages (dominated by MCG, South African Gold Mine Euryarchaeotal Group (SAGMEG) and Halobacteria) within the Ligurian Sea sediments. Bacterial molecular diversity at both sites revealed mostly the presence of the classes Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria within Proteobacteria phylum, and also members of Bacteroidetes phylum. The second most abundant lineages were Actinobacteria and Firmicutes at the Gulf of Lion site and Chloroflexi at the Ligurian Sea site. Various substrates and cultivation conditions allowed us to isolate 75 strains belonging to four lineages: Alpha-, Gammaproteobacteria, Firmicutes and Actinobacteria. In molecular surveys, the Betaproteobacteria group was consistently detected in the Ligurian Sea sediments, characterized by a heterolithic facies with numerous turbidites from a deep-sea levee. Analysis of relative betaproteobacterial abundances and turbidite frequency suggested that the microbial diversity was a result of main climatic changes occurring during the last 20 ka. Statistical direct multivariate canonical correspondence analyses (CCA) showed that the availability of electron acceptors and the quality of electron donors (indicated by age) strongly influenced the community structure. In contrast, within the Gulf of Lion core, characterized by a homogeneous lithological structure of upper-slope environment, most detected groups were Bacteroidetes and, to a lesser extent, Betaproteobacteria. At both site, the detection of Betaproteobacteria coincided with increased terrestrial inputs, as confirmed by the geochemical measurements (Si, Sr, Ti and Ca). In the Gulf of Lion, geochemical parameters were also found to drive microbial community composition. Taken together, our data suggest that the palaeoenvironmental history of erosion and deposition recorded in the Western Mediterranean Sea sediments has left its imprint on the sedimentological context for microbial habitability, and then indirectly on structure and composition of the microbial communities during the late Quaternary. Y1 - 2012 U6 - https://doi.org/10.5194/bg-9-3491-2012 SN - 1726-4170 VL - 9 IS - 9 SP - 3491 EP - 3512 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Green-Saxena, A. A1 - Feyzullayev, A. A1 - Hubert, C. R. J. A1 - Kallmeyer, Jens A1 - Krueger, M. A1 - Sauer, P. A1 - Schulz, Hans-Martin A1 - Orphan, V. J. T1 - Active sulfur cycling by diverse mesophilic and thermophilic microorganisms in terrestrial mud volcanoes of Azerbaijan JF - Environmental microbiology N2 - Terrestrial mud volcanoes (TMVs) represent geochemically diverse habitats with varying sulfur sources and yet sulfur cycling in these environments remains largely unexplored. Here we characterized the sulfur-metabolizing microorganisms and activity in four TMVs in Azerbaijan. A combination of geochemical analyses, biological rate measurements and molecular diversity surveys (targeting metabolic genes aprA and dsrA and SSU ribosomal RNA) supported the presence of active sulfur-oxidizing and sulfate-reducing guilds in all four TMVs across a range of physiochemical conditions, with diversity of these guilds being unique to each TMV. The TMVs varied in potential sulfate reduction rates (SRR) by up to four orders of magnitude with highest SRR observed in sediments where in situ sulfate concentrations were highest. Maximum temperatures at which SRR were measured was 60 degrees C in two TMVs. Corresponding with these trends in SRR, members of the potentially thermophilic, spore-forming, Desulfotomaculum were detected in these TMVs by targeted 16S rRNA analysis. Additional sulfate-reducing bacterial lineages included members of the Desulfobacteraceae and Desulfobulbaceae detected by aprA and dsrA analyses and likely contributing to the mesophilic SRR measured. Phylotypes affiliated with sulfide-oxidizing Gamma- and Betaproteobacteria were abundant in aprA libraries from low sulfate TMVs, while the highest sulfate TMV harboured 16S rRNA phylotypes associated with sulfur-oxidizing Epsilonproteobacteria. Altogether, the biogeochemical and microbiological data indicate these unique terrestrial habitats support diverse active sulfur-cycling microorganisms reflecting the in situ geochemical environment. Y1 - 2012 U6 - https://doi.org/10.1111/1462-2920.12015 SN - 1462-2912 VL - 14 IS - 12 SP - 3271 EP - 3286 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Kallmeyer, Jens A1 - Pockalny, Robert A1 - Adhikari, Rishi Ram A1 - Smith, David C. A1 - D'Hondt, Steven T1 - Global distribution of microbial abundance and biomass in subseafloor sediment JF - Proceedings of the National Academy of Sciences of the United States of America N2 - The global geographic distribution of subseafloor sedimentary microbes and the cause(s) of that distribution are largely unexplored. Here, we show that total microbial cell abundance in subseafloor sediment varies between sites by ca. five orders of magnitude. This variation is strongly correlated with mean sedimentation rate and distance from land. Based on these correlations, we estimate global subseafloor sedimentary microbial abundance to be 2.9 center dot 10(29) cells [corresponding to 4.1 petagram (Pg) C and similar to 0.6% of Earth's total living biomass]. This estimate of subseafloor sedimentary microbial abundance is roughly equal to previous estimates of total microbial abundance in seawater and total microbial abundance in soil. It is much lower than previous estimates of subseafloor sedimentary microbial abundance. In consequence, we estimate Earth's total number of microbes and total living biomass to be, respectively, 50-78% and 10-45% lower than previous estimates. KW - deep biosphere KW - cell enumeration KW - global microbial biomass KW - subsurface life Y1 - 2012 U6 - https://doi.org/10.1073/pnas.1203849109 SN - 0027-8424 VL - 109 IS - 40 SP - 16213 EP - 16216 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Sauer, Patrick A1 - Glombitza, Clemens A1 - Kallmeyer, Jens T1 - A system for incubations at high gas partial pressure JF - Frontiers in microbiology N2 - High-pressure is a key feature of deep subsurface environments. High partial pressure of dissolved gasses plays an important role in microbial metabolism, because thermodynamic feasibility of many reactions depends on the concentration of reactants. For gases, this is controlled by their partial pressure, which can exceed 1 MPa at in situ conditions. Therefore, high hydrostatic pressure alone is not sufficient to recreate true deep subsurface in situ conditions, but the partial pressure of dissolved gasses has to be controlled as well. We developed an incubation system that allows for incubations at hydrostatic pressure up to 60 MPa, temperatures up to 120 degrees C, and at high gas partial pressure. The composition and partial pressure of gasses can be manipulated during the experiment. To keep costs low, the system is mainly made from off-the-shelf components with only very few custommade parts. A flexible and inert PVDF (polyvinylidene fluoride) incubator sleeve, which is almost impermeable for gases, holds the sample and separates it from the pressure fluid. The flexibility of the incubator sleeve allows for sub-sampling of the medium without loss of pressure. Experiments can be run in both static and flow-through mode. The incubation system described here is usable for versatile purposes, not only the incubation of microorganisms and determination of growth rates, but also for chemical degradation or extraction experiments under high gas saturation, e.g., fluid-gas-rock-interactions in relation to carbon dioxide sequestration. As an application of the system we extracted organic compounds from sub-bituminous coal using H2O as well as a H2O-CO2 mixture at elevated temperature (90 degrees C) and pressure (5 MPa). Subsamples were taken at different time points during the incubation and analyzed by ion chromatography. Furthermore we demonstrated the applicability of the system for studies of microbial activity, using samples from the Isis mud volcano. We could detect an increase in sulfate reduction rate upon the addition of methane to the sample. KW - high-pressure incubation system KW - gas partial pressure KW - sub-sampling KW - carbon dioxide KW - low molecular weight organic acids Y1 - 2012 U6 - https://doi.org/10.3389/fmicb.2012.00025 SN - 1664-302X VL - 3 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Nickel, Julia C. A1 - di Primio, Rolando A1 - Mangelsdorf, Kai A1 - Stoddart, Daniel A1 - Kallmeyer, Jens T1 - Characterization of microbial activity in pockmark fields of the SW-Barents Sea JF - Marine geology : international journal of marine geology, geochemistry and geophysics N2 - Multibeam bathymetry revealed the occurrence of numerous craterlike depressions, so-called pockmarks, on the sea floor of the Hammerfest Basin and the Loppa High, south-western Barents Sea. To investigate whether these pockmarks are related to ongoing gas seepage, microbial processes associated with methane metabolism were analyzed using geochemical, biogeochemical and microbiological techniques. Gravity cores were collected along transects crossing individual pockmarks, allowing a direct comparison between different locations inside (assumed activity center), on the rim, and outside of a pockmark (reference sites). Concentrations of hydrocarbons in the sediment, particularly methane, were measured as headspace (free) gas, and in the occluded and adsorbed gas fraction. Down to a depth of 2.6 m below sea floor (mbsf) sulfate reduction rates were quantified by radiotracer incubations. Concentrations of dissolved sulfate in the porewater were determined as well. Neither the sulfate profiles nor the gas measurements show any evidence of microbial activity or active fluid venting. Methane concentrations and sulfate reduction rates were extremely low or even below the detection limit. The results show that the observed sediment structures are most likely paleo-pockmarks, their formation probably occurred during the last deglaciation. KW - pockmark KW - Barents Sea KW - sulfate reduction KW - microbial activity KW - Loppa High Y1 - 2012 U6 - https://doi.org/10.1016/j.margeo.2012.02.002 SN - 0025-3227 VL - 332 IS - 12 SP - 152 EP - 162 PB - Elsevier CY - Amsterdam ER -