An official website of the United States government
Abstract The ongoing global temperature rise enhances permafrost thaw in the Arctic, allowing Pleistocene‐aged frozen soil organic matter to become available for microbial degradation and production of greenhouse gases, particularly methane. Here, we examined the extent and mechanism of anaerobic oxidation of methane (AOM) in the sediments of four interior Alaska thermokarst lakes, which formed and continue to expand as a result of ice‐rich permafrost thaw. In cores of surface (~ 1 m) lake sediments we quantified methane production (methanogenesis) and AOM rates using anaerobic incubation experiments in low (4°C) and high (16°C) temperatures. Methanogenesis rates were measured by the accumulation of methane over ~ 90 d, whereas AOM rates were measured by adding labeled‐13CH4and measuring the produced dissolved inorganic13C. Our results demonstrate that while methanogenesis was vigorous in these anoxic sediments, AOM was lower by two orders of magnitude. In almost all sediment depths and temperatures, AOM rates remained less than 2% of the methanogenesis rates. Experimental evidence indicates that the AOM is strongly related to methanogens, as the addition of a methanogens' inhibitor prevented AOM. Variety of electron acceptor additions did not stimulate AOM, and methanotrophs were scarcely detected. These observations suggest that the AOM signals in the incubation experiments might be a result of enzymatic reversibility (“back‐flux”) during CH4production, rather than thermodynamically favorable AOM. Regardless of the mechanism, the quantitative results show that near surface (< 1‐m) thermokarst sediments in interior Alaska have little to no buffer mechanisms capable of attenuating methane production in a warming climate.
more »
« less
Capturing methane with recombinant soluble methane monooxygenase and recombinant methyl‐coenzyme M reductase
Abstract Methane capture via oxidation is considered one of the ‘Holy Grails’ of catalysis (Tucci and Rosenzweig, 2024). Methane is also a primary greenhouse gas that has to be reduced by 1.2 billion metric tonnes in 10 years to decrease global warming by only 0.23°C (He and Lidstrom, 2024); hence, new technologies are needed to reduce atmospheric methane levels. In Nature, methane is captured aerobically by methanotrophs and anaerobically by anaerobic methanotrophic archaea; however, the anaerobic process dominates. Here, we describe the history and potential of using the two remarkable enzymes that have been cloned with activity for capturing methane: aerobic capture via soluble methane monooxygenase and anaerobic capture via methyl‐coenzyme M reductase. We suggest these two enzymes may play a prominent, sustainable role in addressing our current global warming crisis.
more »
« less
- Award ID(s):
- 2229070
- PAR ID:
- 10537097
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Microbial Biotechnology
- Volume:
- 17
- Issue:
- 8
- ISSN:
- 1751-7915
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The rapid increase of the potent greenhouse gas methane in the atmosphere creates great urgency to develop and deploy technologies for methane mitigation. One approach to removing methane is to use bacteria for which methane is their carbon and energy source (methanotrophs). Such bacteria naturally convert methane to CO2and biomass, a value-added product and a cobenefit of methane removal. Typically, methanotrophs grow best at around 5,000 to 10,000 ppm methane, but methane in the atmosphere is 1.9 ppm. Air above emission sites such as landfills, anaerobic digestor effluents, rice paddy effluents, and oil and gas wells contains elevated methane in the 500 ppm range. If such sites are targeted for methane removal, technology harnessing aerobic methanotroph metabolism has the potential to become economically and environmentally viable. The first step in developing such methane removal technology is to identify methanotrophs with enhanced ability to grow and consume methane at 500 ppm and lower. We report here that some existing methanotrophic strains grow well at 500 ppm methane, and one of them,Methylotuvimicrobium buryatense5GB1C, consumes such low methane at enhanced rates compared to previously published values. Analyses of bioreactor-based performance and RNAseq-based transcriptomics suggest that this ability to utilize low methane is based at least in part on extremely low non-growth-associated maintenance energy and on high methane specific affinity. This bacterium is a candidate to develop technology for methane removal at emission sites. If appropriately scaled, such technology has the potential to slow global warming by 2050.more » « less
-
Abstract Freshwater ecosystem contributions to the global methane budget remains the most uncertain among natural sources. With warming and accompanying carbon release from thawed permafrost and thermokarst lake expansion, the increase of methane emissions could be large. However, the impact and relative importance of various factors related to warming remain uncertain. Based on diverse lake characteristics incorporated in modeling and observational data, we calibrate and verify a lake biogeochemistry model. The model is then applied to estimate global lake methane emissions and examine the impacts of temperature increase for the first and the last decades of the 21st century under different climate scenarios. We find that current emissions are 24.0 ± 8.4 Tg CH4 yr−1from lakes larger than 0.1 km2, accounting for 11% of the global total natural source as estimated based on atmospheric inversion. Future projections under the RCP8.5 scenario suggest a 58%–86% growth in emissions from lakes. Our model sensitivity analysis indicates that additional carbon substrates from thawing permafrost may enhance methane production under warming in the Arctic. Warming enhanced methane oxidation in lake water can be an effective sink to reduce the net release from global lakes.more » « less
-
Climate-induced shifts in sulfate dynamics regulate anaerobic methane oxidation in a coastal wetlandAnaerobic methane oxidation (AMO) is a key microbial pathway that mitigates methane emissions in coastal wetlands, but the response of AMO to changing global climate remains poorly understood. Here, we assessed the response of AMO to climate change in a brackish coastal wetland using a 5-year field manipulation of warming and elevated carbon dioxide (eCO2). Sulfate (SO42−)–dependent AMO (S-DAMO) was the predominant AMO process at our study site due to tidal inputs of SO42−. However, SO42−dynamics responded differently to the treatments; warming reduced SO42−concentration by enhancing SO42−reduction, whileeCO2increased SO42−concentration by enhancing SO42−regeneration. S-DAMO rates mirrored these trends, with warming decreasing S-DAMO rates andeCO2stimulating them. These findings underscore the potential of climate change to alter soil AMO activities through changing SO42−dynamics, highlighting the need to incorporate these processes in predictive models for more accurate representations of coastal wetland methane dynamics.more » « less
-
Abstract. Climate warming perturbs ecosystem carbon (C) cycling, causing both positiveand negative feedbacks on greenhouse gas emissions. In 2016, we began atidal marsh field experiment in two vegetation communities to investigatethe mechanisms by which whole-ecosystem warming alters C gain, viaplant-driven sequestration in soils, and C loss, primarily via methane(CH4) emissions. Here, we report the results from the first 4 years.As expected, warming of 5.1 ∘C more than doubled CH4emissions in both plant communities. We propose this was caused by acombination of four mechanisms: (i) a decrease in the proportion of CH4consumed by CH4 oxidation, (ii) more C substrates available formethanogenesis, (iii) reduced competition between methanogens and sulfate-reducing bacteria, and (iv) indirect effects of plant traits. Plotsdominated by Spartina patens consistently emitted more CH4 than plots dominated bySchoenoplectus americanus, indicating key differences in the roles these common wetland plants playin affecting anaerobic soil biogeochemistry and suggesting that plantcomposition can modulate coastal wetland responses to climate change.more » « less
