Project description:Methanotrophs, which help regulate atmospheric levels of methane, are active in diverse natural and man-made environments. This range of habitats and the feast-famine cycles seen by many environmental methanotrophs suggest that methanotrophs dynamically mediate rates of methane oxidation. Global methane budgets require ways to account for this variability in time and space. Functional gene biomarker transcripts are increasingly being studied to inform the dynamics of diverse biogeochemical cycles. Previously, per-cell transcript levels of the methane oxidation biomarker, pmoA, were found to vary quantitatively with respect to methane oxidation rates in model aerobic methanotroph, Methylosinus trichosporium OB3b. In the present study, these trends were explored for two additional aerobic methanotroph pure cultures, Methylocystis parvus OBBP and Methylomicrobium album BG8. At steady-state conditions, per cell pmoA mRNA transcript levels strongly correlated with per cell methane oxidation across the three methanotrophs across many orders of magnitude of activity (R2 = 0.91). Additionally, genome-wide expression data (RNA-seq) were used to explore transcriptomic responses of steady state M. album BG8 cultures to short-term CH4 and O2 limitation. These limitations induced regulation of genes involved in central carbon metabolism (including carbon storage), cell motility, and stress response.
Project description:Methylated sulfur compounds, including dimethylsulfide (DMS), methylmercaptopropionic acid (MMPA) and methylsulfide (MeSH), are well-documented to play roles in global sulfur cycle and climate homeostasis, yet the molecular mechanisms of how they are metabolized by methanogens remain largely uncharacterized. Here, using high-throughtput sequencing of RNA (RNA-seq), we gained insight into how methanogens respond to methylated sulfur compounds at the transcriptional level.
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.