Lisa Stein is Professor of Climate Change Microbiology within the Faculty of Science - Biological Sciences at the University of Alberta, Canada and will give a talk on:
"Using systems biology tools to link methane and N-cycle processes in hypoxic environments"
Thursday, 7 September 2023
2 pm
Lecture Hall 1, UBB, University of Vienna
Abstract:
Technologies to reduce GHG emissions must take microorganisms into account as this invisible majority is largely responsible for production and consumption of methane and nitrous oxide, the second and third most important GHGs in causing global warming.
Methanogenesis produces most of the methane emitted to the atmosphere, whereas methanotrophic microbes account for methane consumption prior to its emission, plus ca. 1% of atmospheric methane consumption. The primary source of nitrous oxide to the atmosphere is from nitrifying and denitrifying microorganisms whose activity has accelerated over the past 60 years due to anthropogenic input of reactive-N to the biosphere. Interestingly, methanotrophic and nitrifying microbes share common enzymes and metabolic pathways, enabling both groups to produce or consume GHGs depending mainly on redox potential and nitrogen availability. Using the bacterium Methylomicrobium denitrificans FJG1 as a model system, we collected RNAseq, proteomics and metabolomics data across 6-point growth curves to examine the dynamics of methane consumption and nitrous oxide production as a function of oxygen and nitrogen availability. A gene regulatory network of the RNAseq data showed different topologies with either ammonium or nitrate as the N-source, as nitrate is required to induce methane-dependent denitrification to nitrous oxide. With a genome-scale metabolic model under construction, the omics data point to a division of labor in M. denitrificans between fermentation and denitrification at the onset of anoxia and the importance of bacteriohemerythrin as an oxygen delivery system. Extrapolating to natural ecosystems, a similar division of labor and requirement for bacteriohemerythrin has been observed in anoxic freshwater lakes wherein methanotrophs use alternative electron acceptors to consume methane while providing organic molecules from fermentation to cross-feed other microbial populations. However, when nitrate is the alternative electron acceptor, nitrous oxide is produced proportionally to methane consumption. This case-study demonstrates the need to consider the interconnectedness and coevolution of microbial functionality, and to apply omics-based systems biology models when developing and implementing GHG reduction strategies at ecosystem scale.
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