TY - JOUR A1 - Serrano, Paloma A1 - Alawi, Mashal A1 - de Vera, Jean-Pierre Paul A1 - Wagner, Dirk T1 - Response of Methanogenic Archaea from Siberian Permafrost and Non-permafrost Environments to Simulated Mars-like Desiccation and the Presence of Perchlorate JF - Astrobiology N2 - Numerous preflight investigations were necessary prior to the exposure experiment BIOMEX on the International Space Station to test the basic potential of selected microorganisms to resist or even to be active under Mars-like conditions. In this study, methanogenic archaea, which are anaerobic chemolithotrophic microorganisms whose lifestyle would allow metabolism under the conditions on early and recent Mars, were analyzed. Some strains from Siberian permafrost environments have shown a particular resistance. In this investigation, we analyzed the response of three permafrost strains (Methanosarcina soligelidi SMA-21, Candidatus Methanosarcina SMA-17, Candidatus Methanobacterium SMA-27) and two related strains from non-permafrost environments (Methanosarcina mazei, Methanosarcina barkeri) to desiccation conditions (-80 degrees C for 315 days, martian regolith analog simulants S-MRS and P-MRS, a 128-day period of simulated Mars-like atmosphere). Exposure of the different methanogenic strains to increasing concentrations of magnesium perchlorate allowed for the study of their metabolic shutdown in a Mars-relevant perchlorate environment. Survival and metabolic recovery were analyzed by quantitative PCR, gas chromatography, and a new DNA-extraction method from viable cells embedded in S-MRS and P-MRS. All strains survived the two Mars-like desiccating scenarios and recovered to different extents. The permafrost strain SMA-27 showed an increased methanogenic activity by at least 10-fold after deep-freezing conditions. The methanogenic rates of all strains did not decrease significantly after 128 days S-MRS exposure, except for SMA-27, which decreased 10-fold. The activity of strains SMA-17 and SMA-27 decreased after 16 and 60 days P-MRS exposure. Non-permafrost strains showed constant survival and methane production when exposed to both desiccating scenarios. All strains showed unaltered methane production when exposed to the perchlorate concentration reported at the Phoenix landing site (2.4 mM) or even higher concentrations. We conclude that methanogens from (non-)permafrost environments are suitable candidates for potential life in the martian subsurface and therefore are worthy of study after space exposure experiments that approach Mars-like surface conditions. KW - Methanogenic archaea KW - Simulated Mars-like conditions KW - Subfreezing temperatures KW - Martian regolith analogs KW - Perchlorate KW - Permafrost Y1 - 2019 U6 - https://doi.org/10.1089/ast.2018.1877 SN - 1531-1074 SN - 1557-8070 VL - 19 IS - 2 SP - 197 EP - 208 PB - Liebert CY - New Rochelle ER - TY - JOUR A1 - Heslop, J. K. A1 - Anthony, K. M. Walter A1 - Grosse, Guido A1 - Liebner, Susanne A1 - Winkel, Matthias T1 - Century-scale time since permafrost thaw affects temperature sensitivity of net methane production in thermokarst-lake and talik sediments JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - Permafrost thaw subjects previously frozen soil organic carbon (SOC) to microbial degradation to the greenhouse gases carbon dioxide (CO2) and methane (CH4). Emission of these gases constitutes a positive feedback to climate warming. Among numerous uncertainties in estimating the strength of this permafrost carbon feedback (PCF), two are: (i) how mineralization of permafrost SOC thawed in saturated anaerobic conditions responds to changes in temperature and (ii) how microbial communities and temperature sensitivities change over time since thaw. To address these uncertainties, we utilized a thermokarst-lake sediment core as a natural chronosequence where SOC thawed and incubated in situ under saturated anaerobic conditions for up to 400 years following permafrost thaw. Initial microbial communities were characterized, and sediments were anaerobically incubated in the lab at four temperatures (0 °C, 3 °C, 10 °C, and 25 °C) bracketing those observed in the lake's talik. Net CH4 production in freshly-thawed sediments near the downward-expanding thaw boundary at the base of the talik were most sensitive to warming at the lower incubation temperatures (0 °C to 3 °C), while the overlying sediments which had been thawed for centuries had initial low abundant methanogenic communities (< 0.02%) and did not experience statistically significant increases in net CH4 production potentials until higher incubation temperatures (10 °C to 25 °C). We propose these observed differences in temperature sensitivities are due to differences in SOM quality and functional microbial community composition that evolve over time; however further research is necessary to better constrain the roles of these factors in determining temperature controls on anaerobic C mineralization. KW - Carbon KW - Lake sediments KW - Methane KW - Permafrost KW - Talik KW - Temperature sensitivity Y1 - 2019 U6 - https://doi.org/10.1016/j.scitotenv.2019.06.402 SN - 0048-9697 SN - 1879-1026 VL - 691 SP - 124 EP - 134 PB - Elsevier CY - Amsterdam ER -