Project description:Natural and anthropogenic wetlands are main sources of the atmospheric greenhouse gas methane. Methane emissions from wetlands are mitigated by methanotrophic microorganisms and by processes at the oxic-anoxic interface, such as sulfur cycling, that reduce the activity of methanogens. In this study, we obtained a pure culture (strain HY1) of a versatile wetland methanotroph that oxidizes various organic and inorganic compounds. This strain represents (i) the first isolate that can aerobically oxidize both methane and reduced sulfur compounds and (ii) a new alphapoteobacterial species, named Candidatus Methylovirgula thiovorans. Genomic and proteomic analyses showed that soluble methane monooxygenase and XoxF-type alcohol dehydrogenases are the only enzymes for methane and methanol oxidation, respectively. Unexpectedly, strain HY1 harbors various pathways for respiratory sulfur oxidation and oxidized reduced sulfur compounds to sulfate using the Sox-rDsr pathway (without SoxCD) and the S4I system. It employed the Calvin-Benson-Bassham cycle for CO2 fixation during chemolithoautotrophic growth on the reduced sulfur compounds. Methane and thiosulfate were independently and simultaneously oxidized by strain HY1 for growth. Proteomic and microrespiratory analyses showed that the metabolic pathways for methane and thiosulfate oxidation were induced in the presence of their substrates. The discovery of this versatile methanotroph demonstrates that methanotrophy and thiotrophy is compatible in a single bacterium and adds a new aspect to interactions of methane and sulfur cycles in oxic-anoxic interface environments.
2022-07-11 | PXD025979 | Pride
Project description:Methane oxidation coupled to denitrification
Project description:To obtain deeper understanding of atmospheric dynamics of the potent greenhouse gas methane, controlling factors of methanotrophs, as the sole biological methane sink, is necessary. Recent research has revealed complex interactions between methanotrophs and heterotrophs, involving volatile organic compounds (VOCs). In environments with high methane concentrations VOC-mediated interactions significantly influence methane cycling and emissions. Here, we employed a multidisciplinary approach, utilizing proteomics, volatile analysis, and measurements of bacterial growth and methane oxidation to elucidate underlying mechanisms of VOC-mediated interactions between heterotrophs and methanotrophs. The results demonstrate that specific VOCs, like dimethylpolysulfides, released by heterotrophic bacteria can inhibit growth and methane uptake of methanotrophs, while other VOCs had the opposite effect. Proteomics analysis revealed differential protein expression patterns depending on exposure to the volatolome of a heterotrophic bacterium or with CO2 added, which was most pronounced with the particulate and soluble methane monooxygenase. The current study demonstrated potential biotic modulation of methanotrophy without direct contact, caused by VOC or CO2 from respiration, or both, with a proteomic response. Although further research is needed to elucidate the specific mechanisms involved, it is clear that methanotroph-heterotroph interactions need to be investigated closer to informs strategies for mitigating emission of the greenhouse gas methane.
Project description:Sulfate-reducing bacteria (SRB) are ubiquitously distributed across various biospheres and play key roles in global sulfur and carbon cycles. However, few deep-sea SRB have been cultivated and studied in situ, limiting our understanding of the true metabolism of SRB in the deep biosphere. Here, we firstly clarified the high abundance of SRB in deep-sea sediments via the operational taxonomic units (OTU) sequencing analysis. We have successfully isolated a sulfate-reducing bacterium (strain zrk46) from a cold seep sediment, by using an enriched medium supplemented with sulfate. Our genomic, physiological and phylogenetic analyses indicate that strain zrk46 is a novel species, which we propose be named: Pseudodesulfovibrio serpens. Based on the combined results from growth assays and proteomic analyses, we found that supplementation with sulfate (SO42-), thiosulfate (S2O32-), or sulfite (SO32-) promoted the growth of strain zrk46 by facilitating energy production through the dissimilatory sulfate reduction with the auxiliary functions of heterodisulfide reductases, ferredoxins, and nitrate reduction associated proteins, which were coupled to the oxidation of environmental organic matter in both laboratory and deep-sea in situ conditions. Moreover, metatranscriptomic results have also confirmed the dissimilatory sulfate reduction of deep-sea SRB in in situ environment, which might be coupled to the methane oxidation of anaerobic methanotrophic archaea (ANME-2). Overall, these findings expand our understanding of deep-sea SRB, while highlighting their importance for deep-sea sulfur and carbon cycles.
Project description:Transcriptional profiling of methanotrophic bacteria (pmoA gene) in methane oxidation biocover soil by depth Three-different depth condition in methane oxidation biocover soil: top, middle and botton layer soil: genomic DNA extract. Three replicate per array.