Genomic and enzymatic evidence of acetogenesis by anaerobic methanotrophic archaea
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ABSTRACT:
SUBMITTER: Shanshan,Yang
REPOSITORIES: NODE
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Project description:Anaerobic oxidation of methane (AOM) mediated by anaerobic methanotrophic archaea (ANME) is the primary process that provides energy to cold seep ecosystems by converting methane into inorganic carbon. Notably, cold seep ecosystems are dominated by highly divergent heterotrophic microorganisms. The role of the AOM process in supporting heterotrophic population remains unknown. We investigate the acetogenic capacity of ANME-2a in a simulated cold seep ecosystem using high-pressure biotechnology, where both AOM activity and acetate production are detected. The production of acetate from methane is confirmed by isotope-labeling experiments. A complete archaeal acetogenesis pathway is identified in the ANME-2a genome, and apparent acetogenic activity of the key enzymes ADP-forming acetate-CoA ligase and acetyl-CoA synthetase is demonstrated. Here, we propose a modified model of carbon cycling in cold seeps: during AOM process, methane can be converted into organic carbon, such as acetate, which further fuels the heterotrophic community in the ecosystem.
| S-EPMC7414198 | biostudies-literature
Project description:propose a modified model of carbon cycling in cold seeps: during the classic AOM process, methane can be converted into organic carbon, such as acetate, which further fuels the larger heterotrophic community in the ecosystem
| OEX003082 | NODE
Project description:propose a modified model of carbon cycling in cold seeps: during the classic AOM process, methane can be converted into organic carbon, such as acetate, which further fuels the larger heterotrophic community in the ecosystem
| OEX003083 | NODE
Project description:propose a modified model of carbon cycling in cold seeps: during the classic AOM process, methane can be converted into organic carbon, such as acetate, which further fuels the larger heterotrophic community in the ecosystem
| OEX003084 | NODE
Project description:propose a modified model of carbon cycling in cold seeps: during the classic AOM process, methane can be converted into organic carbon, such as acetate, which further fuels the larger heterotrophic community in the ecosystem
| OEX003085 | NODE
Project description:Microbial communities in hydrothermally active sediments of the Guaymas Basin (Gulf of California, Mexico) were studied by using 16S rRNA sequencing and carbon isotopic analysis of archaeal and bacterial lipids. The Guaymas sediments harbored uncultured euryarchaeota of two distinct phylogenetic lineages within the anaerobic methane oxidation 1 (ANME-1) group, ANME-1a and ANME-1b, and of the ANME-2c lineage within the Methanosarcinales, both previously assigned to the methanotrophic archaea. The archaeal lipids in the Guaymas Basin sediments included archaeol, diagnostic for nonthermophilic euryarchaeota, and sn-2-hydroxyarchaeol, with the latter compound being particularly abundant in cultured members of the Methanosarcinales. The concentrations of these compounds were among the highest observed so far in studies of methane seep environments. The delta-(13)C values of these lipids (delta-(13)C = -89 to -58 per thousand) indicate an origin from anaerobic methanotrophic archaea. This molecular-isotopic signature was found not only in samples that yielded predominantly ANME-2 clones but also in samples that yielded exclusively ANME-1 clones. ANME-1 archaea therefore remain strong candidates for mediation of the anaerobic oxidation of methane. Based on 16S rRNA data, the Guaymas sediments harbor phylogenetically diverse bacterial populations, which show considerable overlap with bacterial populations of geothermal habitats and natural or anthropogenic hydrocarbon-rich sites. Consistent with earlier observations, our combined evidence from bacterial phylogeny and molecular-isotopic data indicates an important role of some novel deeply branching bacteria in anaerobic methanotrophy. Anaerobic methane oxidation likely represents a significant and widely occurring process in the trophic ecology of methane-rich hydrothermal vents. This study stresses a high diversity among communities capable of anaerobic oxidation of methane.
| S-EPMC123873 | biostudies-literature
Project description:Thawing submarine permafrost is a source of methane to the subsurface biosphere. Methane oxidation in submarine permafrost sediments has been proposed, but the responsible microorganisms remain uncharacterized. We analyzed archaeal communities and identified distinct anaerobic methanotrophic assemblages of marine and terrestrial origin (ANME-2a/b, ANME-2d) both in frozen and completely thawed submarine permafrost sediments. Besides archaea potentially involved in anaerobic oxidation of methane (AOM) we found a large diversity of archaea mainly belonging to Bathyarchaeota, Thaumarchaeota, and Euryarchaeota. Methane concentrations and δ13C-methane signatures distinguish horizons of potential AOM coupled either to sulfate reduction in a sulfate-methane transition zone (SMTZ) or to the reduction of other electron acceptors, such as iron, manganese or nitrate. Analysis of functional marker genes (mcrA) and fluorescence in situ hybridization (FISH) corroborate potential activity of AOM communities in submarine permafrost sediments at low temperatures. Modeled potential AOM consumes 72-100% of submarine permafrost methane and up to 1.2 Tg of carbon per year for the total expected area of submarine permafrost. This is comparable with AOM habitats such as cold seeps. We thus propose that AOM is active where submarine permafrost thaws, which should be included in global methane budgets.
| S-EPMC5778128 | biostudies-literature
Project description:Microbially mediated anaerobic oxidation of methane (AOM) is a key process in the regulation of methane emissions to the atmosphere. Iron can serve as an electron acceptor for AOM, and it has been suggested that Fe(III)-dependent AOM potentially comprises a major global methane sink. Although it has been proposed that anaerobic methanotrophic (ANME) archaea can facilitate this process, their active metabolic pathways have not been confirmed. Here we report the enrichment and characterisation of a novel archaeon in a laboratory-scale bioreactor fed with Fe(III) oxide (ferrihydrite) and methane. Long-term performance data, in conjunction with the 13C- and 57Fe-labelling batch experiments, demonstrated that AOM was coupled to Fe(III) reduction to Fe(II) in this bioreactor. Metagenomic analysis showed that this archaeon belongs to a novel genus within family Candidatus Methanoperedenaceae, and possesses genes encoding the "reverse methanogenesis" pathway, as well as multi-heme c-type cytochromes which are hypothesised to facilitate dissimilatory Fe(III) reduction. Metatranscriptomic analysis revealed upregulation of these genes, supporting that this archaeon can independently mediate AOM using Fe(III) as the terminal electron acceptor. We propose the name Candidatus "Methanoperedens ferrireducens" for this microorganism. The potential role of "M. ferrireducens" in linking the carbon and iron cycles in environments rich in methane and iron should be investigated in future research.
| S-EPMC6052012 | biostudies-literature
Project description:Cell proliferation is achieved by numerous enzyme reactions. Temperature governs the activity of each enzyme, which overall determines the optimal growth temperature. Synthesizing useful chemicals and fuels utilizes only part of the metabolic pathways, especially the central metabolic pathways such as glycolysis and TCA cycle to metabolize glucose. However, the optimal temperature for the activity of the central metabolic pathways is inconclusive whether it is correlated with the optimal temperature for cell proliferation. Here, we found that Corynebacterium glutamicum wild type increased the metabolic activity to consume glucose under anaerobic (oxygen deprived) conditions at 42.5ºC, in which the cell hardly grows under aerobic conditions. Glucose consumption rate was increased by 24% at 42.5ºC compared to that at the optimal growth temperature of 30.0ºC. Transcriptional analysis showed that gapX gene encoding glycelaldehydre-3-phosphate dehydrogenase, glucokinase gene, and a gene involved in glucose uptake were upregulated at 42.5ºC. Production of fermentative lactate was increased by 69% than that at 30.0ºC, whereas succinate production was decreased by 13%. In addition to several glycolytic enzymes, the activity of pyruvate kinase was increased with increasing the temperature, whereas the activity of phosphoenolpyruvate carboxylase in anapleotic pathway leading to succinate synthesis was decreased. However, a metabolically engineered succinate over-producing strain, in which lactate production was shut off and pyruvate carboxylase encoding gene in another anapleotic pathway was overexpressed, produced 34% higher succinate at 42.5ºC than that at 30.0ºC with increased glucose consumption. This study provides the evidence that the optimal reaction temperature for production of fermentative products can be set beyond upper limit of growth temperature in C. glutamicum, and hence it could be applicable for producing various chemicals and fuels in C. glutamicum under anaerobic conditions and non-growing cell reactions in other microorganisms.
2020-06-23 | GSE123063 | GEO
Project description:Sulfate is the predominant electron acceptor for anaerobic oxidation of methane (AOM) in marine sediments. This process is carried out by a syntrophic consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria (SRB) through an energy conservation mechanism that is still poorly understood. It was previously hypothesized that ANME alone could couple methane oxidation to dissimilatory sulfate reduction, but a genetic and biochemical basis for this proposal has not been identified. Using comparative genomic and phylogenetic analyses, we found the genetic capacity in ANME and related methanogenic archaea for sulfate reduction, including sulfate adenylyltransferase, APS kinase, APS/PAPS reductase and two different sulfite reductases. Based on characterized homologs and the lack of associated energy conserving complexes, the sulfate reduction pathways in ANME are likely used for assimilation but not dissimilation of sulfate. Environmental metaproteomic analysis confirmed the expression of 6 proteins in the sulfate assimilation pathway of ANME. The highest expressed proteins related to sulfate assimilation were two sulfite reductases, namely assimilatory-type low-molecular-weight sulfite reductase (alSir) and a divergent group of coenzyme F420-dependent sulfite reductase (Group II Fsr). In methane seep sediment microcosm experiments, however, sulfite and zero-valent sulfur amendments were inhibitory to ANME-2a/2c while growth in their syntrophic SRB partner was not observed. Combined with our genomic and metaproteomic results, the passage of sulfur species by ANME as metabolic intermediates for their SRB partners is unlikely. Instead, our findings point to a possible niche for ANME to assimilate inorganic sulfur compounds more oxidized than sulfide in anoxic marine environments.
| S-EPMC6286981 | biostudies-literature