Impact of microorganisms as sinks of atmospheric chloromethane

Background/Summary

The project CHLOROFILTER is an interdisciplinary consortium of two French and two German partners who combine expertizes and knowledge to address the impact of microorganisms on the global budget of chloromethane (CH₃Cl). Anthropogenic emissions of ozone-depleting compounds have been strongly reduced since the Montreal Protocol came into force in 1989. As a consequence, compounds released from natural sources, have become increasingly relevant in stratospheric ozone depletion. CH₃Cl is the most abundant halogenated compound in the atmosphere, and originates primarily from terrestrial ecosystems. Future warmer climates will likely lead to increased CH₃Cl emissions. Current estimates of its global budget are uncertain but suggest that microorganisms play a more important role in degradation of atmospheric CH₃Cl than previously thought. Methylotrophic microbes, some with the capability to degrade CH₃Cl, occur in soils, the phyllosphere of many plants, and have recently been reported to be active in water droplets of clouds. The main objective of CHLOROFILTER is to provide quantitative information on process-level and in depth genetic insights into these microbes.

The investigations focus on kinetic and isotope effects upon CH₃Cl degradation by methylotrophs associated with soils, plants, and clouds to resolve the quantitative relevance of microbial sinks for the global CH₃Cl budget. The microbial community will be characterized in selected various environmental samples using a taxonomical (16S RNA genes) and a functional gene marker for CH₃Cl degradation (cmuA). Furthermore, selected samples of soil, plants, and cloud water will be subjected to ¹³CH₃Cl in order to label the biomass of CH₃Cl degrading microbes and to retrieve ¹³C-labeled metagenomes via DNA stable isotope probing to assess the diversity of microbial pathways for CH₃Cl-degradation.

An improved quantitative understanding of the sources and sinks of atmospheric CH₃Cl will be invaluable for our understanding the stratospheric chlorine chemistry and predict ozone layer stability.

Relevant publications

·         F. Keppler, A.N. Röhling, N. Jaeger, M. Schroll, S.C. Hartmann, M. Greule (2020). Sources and sinks of chloromethane in a salt marsh ecosystem: constraints from concentration and stable isotope measurements of laboratory incubation experiments. Environmental Science: Processes & Impact, DOI: 10.1039/C9EM00540D.

·         F. Keppler, J.D. Barnes, A. Horst, E. Bahlmann, J. Luo, T. Nadalig, M. Greule, S.C. Hartmann, S. Vuilleumier (2020). Chlorine isotope fractionation of the major chloromethane sinks in the environment. Environmental Science & Technology, 54, 1634-1645.

·         F. Bringel, L. Besaury, P. Amato, E. Kröber, S. Kolb, F. Keppler, S. Vuilleumier, T. Nadalig (2019). Methylotrophs and methylotroph populations for chloromethane degradation. Current Issues in Molecular Biology, 33, 149-172.

·         N. Jaeger, L. Besaury, A.N. Röhling, F. Koch, A.-M. Delort, C. Gasc, M. Greule, S. Kolb, T. Nadalig, P. Peyret, S. Vuilleumier, P. Amato, F. Bringel, F. Keppler (2018). Chloromethane formation and degradation in the fern phyllosphere. Science of the Total Environment, 634, 1278-1287.

·         N. Jaeger, L. Besaury, E. Kröber, A.-M. Delort, M. Greule, K. Lenhart, T. Nadalig, S. Vuilleumier, P. Amato, S. Kolb, F. Bringel, F. Keppler (2018). New insights into chloromethane degradation in soils gained using a combined microbial and two-dimensional stable isotope approach. Journal of Environmental Quality, 47, 254-262.