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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase (RubisCO) Is Essential for Growth of the Methanotroph Methylococcus capsulatus Strain Bath

The importance of RubisCO and CO 2 in M. capsulatus Bath metabolism is unclear. In this study, we demonstrated that both CO 2 and RubisCO are essential for M. capsulatus Bath growth. 13 CO 2 tracing experiments supported that RubisCO mediates CO 2 fixation and that a noncanonical Calvin cycle is active in this organism.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Evolutionary diversification of methanotrophic ANME-1 archaea and their expansive virome

' Candidatus Methanophagales' (ANME-1) is an order-level clade of archaea responsible for anaerobic methane oxidation in deep-sea sediments. The diversity, ecology and evolution of ANME-1 remain poorly understood. In this study, we use metagenomics on deep-sea hydrothermal samples to expand ANME-1 diversity and uncover the effect of virus–host dynamics. Phylogenetic analyses reveal a deep-branching, thermophilic family, ' Candidatus Methanospirareceae', closely related to short-chain alkane oxidizers. Global phylogeny and near-complete genomes show that hydrogen metabolism within ANME-1 is an ancient trait that was vertically inherited but differentially lost during lineage diversification. Metagenomics also uncovered 16 undescribed virus families so far exclusively targeting ANME-1 archaea, showing unique structural and replicative signatures. The expansive ANME-1 virome contains a metabolic gene repertoire that can influence host ecology and evolution through virus-mediated gene displacement. Our results suggest an evolutionary continuum between anaerobic methane and short-chain alkane oxidizers and underscore the effects of viruses on the dynamics and evolution of methane-driven ecosystems.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1993

Ecophysiological Characteristics of Obligate Methanotrophic Bacteria and Methane Oxidation In Situ

Most of the obligate methane-oxidizing bacteria (MOB) described to date are neutrophilic mesophiles that grow optimally in dilute media. Kinetic analyses generally indicate that bacterial methane uptake occurs by transport systems with a K(sub m) greater than l micronM. These and other properties of MOB are inconsistent with characteristics of methane oxidation in situ. The inconsistencies indicate a need for greater attention to the ecophysiological characteristics of isolates and the design of enrichment and isolation schemes which emphasize ecologically relevant parameters (e.g., low temperature, limited and diverse substrate availability, low water potential).

King, Gary M.↗
DOE OSTI2021

Two TonB-dependent transporters in Methylosinus trichosporium OB3b are responsible for uptake of different forms of methanobactin and are involved in the canonical ‘copper switch’

Copper is an important component of methanotrophic physiology as it controls the expression and activity of alternative forms of methane monooxygenase (MMO). To collect copper, some methanotrophs secrete a chalkophore or copper-binding compound called methanobactin (MB). MB is a ribosomally synthesized post-translationally modified polypeptide (RiPP) that, after binding copper, is collected by MbnT, a TonB-dependent transporter (TBDT). Structurally different forms of MB have been characterized, and here we show that different forms of MB are collected by specific TBDTs. Further, we report that in the model methanotroph, Methylosinus trichosporium OB3b, expression of the TBDT required for uptake of a different MB made by Methylocystis sp. strain SB2 (MB-SB2), is induced in the presence of MB-SB2, suggesting that methanotrophs have developed specific machinery and regulatory systems to actively take up MB from other methanotrophs for copper collection. Moreover, the canonical “copper-switch” in Ms. trichosporium OB3b that controls expression of alternative MMOs is apparent if one of the two TBDTs required for MB-OB3b and MB-SB2 uptake is knocked out, but is disrupted if both TBDTs are knocked out. Furthermore, these data indicate that MB uptake, including the uptake of exogenous MB, plays an important role in the copper switch in M. trichosporium OB3b and thus overall activity. Based on these data, we propose a revised model for the “copper-switch” in this methanotroph that involves MB uptake.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Characterization and microbial mitigation of fugitive methane emissions from oil and gas wells: Example from Indiana, USA

Hydrocarbon gas emissions from active, inactive, and improperly sealed or abandoned oil/gas wells significantly contribute to anthropogenically emitted greenhouse gases, predominantly in the form of methane (CH 4 ). We explored the extent of hydrocarbon gas emissions from 20 active, inactive, plugged and abandoned oil/gas wells in Indiana (USA), where it is estimated that there are more than 80,000 well sites throughout the state. After this initial survey, using a static flux tent, we quantified fugitive CH4 emissions from an active gas well to approximately 2 L h -1 . To evaluate the potential for microbial mitigation of hydrocarbon emissions to the atmosphere, we conducted laboratory microcosm experiments to quantify the CH 4 oxidizing potential of soils collected from sites with varying distances to the leaking gas well. Soils in close proximity to the well (0.5 m) efficiently consumed nearly all (97 %) of the added CH 4 , while only 14 % of added CH 4 was consumed by soils that were more distant from the well (20 m). These results suggest that fugitive CH 4 emissions enrich methanotrophic bacteria in soils immediately adjacent to the well. Consistent with this view, we found that prolonged exposure of soils to elevated concentrations of CH 4 enhanced the methanotrophic activity. Together, these findings prompted us to design a “methanotrophic soil mound” to assess the feasibility of mitigating point sources of CH 4 by harnessing the natural methanotrophic capacity of soil microbial communities. We found that a methanotrophic soil mound from a landfill could sustainably mitigate the CH 4 emission from the artificial source, providing a promising low-cost solution to ameliorate fugitive CH 4 emissions from abandoned oil and gas wells to the atmosphere. Finally, the effectiveness of microbe-based remediation is limited in cold climates and arid environments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Thaw Transitions and Redox Conditions Drive Methane Oxidation in a Permafrost Peatland

Thawing permafrost, ground that has been frozen for 2 or more years, often results in wet conditions that promote the production of methane (CH 4 ). Methane is a greenhouse gas that is over 30 times more powerful than carbon dioxide at warming the atmosphere. Microorganisms called methanotrophs can consume a substantial portion of this CH 4 before it reaches the atmosphere, but the extent of this consumption is not well understood. Methanotrophs are affected by environmental conditions, such as oxygen availability, that change with permafrost thaw. We used laboratory experiments to measure how quickly methanotrophs consume CH 4 from sites within a permafrost peatland with little, intermediate, and full permafrost thaw. We found that CH 4 consumption increased as permafrost thawed and that sites transitioning between thaw stages had a different potential to consume CH 4 than intact and fully thawed sites. Methane consumption was also high in locations with low dissolved oxygen, which suggests that methanotrophs in these sites may tolerate low oxygen conditions in the field. We found that redox potential, a measurement that describes the tendency for a compound to be oxidized or reduced, was a strong predictor of CH 4 consumption in partially and fully thawed sites. Overall, these measurements highlight the potential for methanotrophs to mitigate CH 4 emissions in peatlands with thawing permafrost and provide new insights to modeling CH 4 dynamics across the full thaw gradient.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Isolation of Methane Enriched Bacterial Communities and Application as Wheat Biofertilizer under Drought Conditions: An Environmental Contribution

The search for methanotrophs as plant-growth-promoting rhizobacteria (PGPR) presents an important contribution to mitigating the impact of global warming by restoring the natural soil potential for consuming methane while benefiting plants during droughts. Our in silico simulations suggest that water, produced as a byproduct of methane oxidation, can satisfy the cell growth requirement. In addition to water, methanotrophs can produce metabolites that stimulate plant growth. Considering this, we proposed that applying methanotrophs as PGPR can alleviate the effect of droughts on crops, while stimulating atmospheric methane consumption. In this work, we isolated a series of methanotrophic communities from the rhizospheres of different crops, including Italian sweet pepper and zucchini, using an atmosphere enriched with pure methane gas, to determine their potential for alleviating drought stress in wheat plants. Subsequently, 23 strains of nonmethanotrophic bacteria present in the methanotrophic communities were isolated and characterized. We then analyzed the contribution of the methane-consuming consortia to the improvement of plant growth under drought conditions, showing that some communities contributed to increases in the wheat plants’ lengths and weights, with statistically significant differences according to ANOVA models. Furthermore, we found that the presence of methane gas can further stimulate the plant–microbe interactions, resulting in larger plants and higher drought tolerance.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Variable Inhibition of Nitrous Oxide Reduction in Denitrifying Bacteria by Different Forms of Methanobactin

Aerobic methanotrophic activity is highly dependent on copper availability, and methanotrophs have developed multiple strategies to collect copper. Specifically, when copper is limiting (ambient concentrations < 1 μM), some methanotrophs produce and secret a small modified peptide (< 1,300 Da) termed methanobactin (MB) that binds copper with high affinity. As MB is secreted into the environment, other microbes that require copper for their metabolism may be inhibited as MB may make copper unavailable; e.g., inhibition of denitrifiers as complete conversion nitrate to dinitrogen involves multiple enzymes, some of which are copper-dependent. Of key concern is inhibition of the copper-dependent nitrous oxide reductase (NosZ), the only known enzyme capable of converting nitrous oxide (N 2 O) to dinitrogen. Herein, we show that different forms of MB differentially affect copper uptake and N2O reduction by Pseudomonas stutzeri strain DCP-Ps1 (that expresses clade I NosZ) and Dechloromonas aromatica strain RCB (that expresses clade II NosZ). Specifically, in the presence of MB from Methylocystis sp. strain SB2 (SB2-MB), copper uptake and nosZ expression were more significantly reduced than in the presence of MB from Methylosinus trichosporium OB3b (OB3b-MB). Further, N2O accumulation increased more significantly for both P. stutzeri strain DCP-Ps1 and D. aromatica strain RCB in the presence of SB2-MB versus OB3b-MB. These data illustrate that copper competition between methanotrophs and denitrifying bacteria can be significant and that the extent of such competition is dependent on the form of MB that methanotrophs produce.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Impacts of The Wetland Sedge Carex aquatilis on Microbial Community and Methane Metabolisms

Microbial activity in the soil of wetlands is responsible for the emission of more methane to the atmosphere than all other natural sources combined. This microbial activity is heavily impacted by plant roots, which influence the microbial community by exuding organic compounds and by leaking oxygen into an otherwise anoxic environment. This study compared the microbial communities of planted and unplanted wetland soil from an Alaskan bog to elucidate how plant growth influences populations and metabolisms of methanogens and methanotrophs. A common boreal wetland sedge, Carex aquatilis, was grown in the laboratory and DNA samples were sequenced from the rhizosphere, unplanted bulk soil, and a simulated rhizosphere with oxygen input but no organic carbon. The abundance of both methanogens and methanotrophs were positively correlated with methane emissions. Among the methanotrophs, both aerobic and anaerobic methane oxidizing microbes were more common in the rhizosphere of mature plants than in unplanted soil, while facultative methanotrophs capable of utilizing either methane or other molecules became relatively less common. Furthermore, these trends indicate that the roots in this experiment created an environment which favored highly specialized microbial metabolisms over generalist approaches. One aspect of this specialized microbiome is the presence of both aerobic and anaerobic metabolisms, which indicates that oxygen is present but is a limiting resource controlling competition.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Systems Level Understanding of Interconnected Methane and Nitrogen Cycles Using Complex Synthetic Communities

The main goal of this project was to follow up on prior discovery of the communal nature of methane utilization by the aerobic methanotrophic bacteria, resulting in carbon transfer along a food chain. This goal was approached via manipulation of specially designed, synthetic bacterial communities, fed exclusively by methane, under a variety of simulated environmental conditions. Using (meta)genomics, metatranscriptomics, stable isotope probing and mutant generation, we obtained solid evidence for the nature of the core microbiota involved in collaborative methane consumption, the major players (true methanotrophs) being the members of the family Methylococcaceae, their major partners (non-methanotrophic methylotrophs) being members of the family Methylophilaceae, and minor but persistent partners in the communities being members of the orders Burkholderiales and Bacteroidetes. Metabolic reconstruction from single genomes and metagenome-assembled genomes (MAGs), along with metatranscriptomics results delineated major pathways for carbon metabolism, suggesting that the methanotrophs share different organic compounds with different functional guilds: methanol with Methylophilaceae, acetate with Burkholderiales, and polymeric substances with Bacteroidetes. Overall, the results of this project expand our understanding of microbial metabolism of methane and, thus, provide basis for strategies for microbial methane mitigation, with obvious benefits to the society of the United States and worldwide.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1996

Regulation of Methane Oxidation in a Freshwater Wetland by Water Table Changes and Anoxia

The effects of water table fluctuations and anoxia on methane emission and methane oxidation were studied in a freshwater marsh. Seasonal aerobic methane oxidation rates varied between 15% and 76% of the potential diffusive methane flux (diffusive flux in the absence of aerobic oxidation). On an annual basis, approximately 43% of the methane diffusing into the oxic zone was oxidized before reaching the atmosphere. The highest methane oxidation was observed when the water table was below the peat surface. This was confirmed in laboratory experiments where short-term decreases in water table levels increased methane oxidation but also net methane emission. Although methane emission was generally not observed during the winter, stems of soft rush (Juncus effusus) emitted methane when the marsh was ice covered. Indigenous methanotrophic bacteria from the wetiand studied were relatively anoxia tolerant. Surface peat incubated under anoxic conditions maintained 30% of the initial methane oxidation capacity after 32 days of anoxia. Methanotrophs from anoxic peat initiated aerobic methane oxidation relatively quickly after oxygen addition (1-7 hours). These results were supported by culture experiments with the methanotroph Methylosinus trichosporium OB3b. This organism maintained a greater capacity for aerobic methane oxidation when starved under anoxic compared to oxic conditions. Anoxic incubation of M. trichosporium OB3b in the presence of sulfide (2 mM) and a low redox potential (-110 mV) did not decrease the capacity for methane oxidation relative to anoxic cultures incubated without sulfide. The results suggest that aerobic methane oxidation was a major regulator of seasonal methane emission front the investigated wetland. The observed water table fluctuations affected net methane oxidation presumably due to associated changes in oxygen gradients. However, changes from oxic to anoxic conditions in situ had relatively little effect on survival of the methanotrophic bacteria and thus on methane oxidation potential per se.

Roslev, Peter↗