Impact of Alternative Substrates on Methane, Methanol, and Chloromethane Metabolism of Methylotrophs in Forest Soils
Final Report Abstract
Methylotrophic microorganisms are important sinks of atmosphere relevant compounds such as methane, methanol and chloromethane. These volatile organic compounds (VOCs) affect the global climate as greenhouse gases (GHGs), i.e. methane, and the atmospheric chemistry, i.e. may degrade the stratospheric ozone layer or reduce the oxidative capacity of the troposphere. The second effect in turn leads to longer persistence of GHGs in the troposphere and thereby stronger impact of GHGs. Methylotrophic microorganisms are the major biological sink of these compounds in the environment. Although methylotrophs have been an object of research object more than one century, the knowledge on environmental factors that drive their biodiversity and acitivity in terrestrial ecosystems have been hardly resolved. Top soil is a preferred habitat for methylotrophs. Most soil-derived methylotrophs are neutrophilic and facultatively methylotrophic, which suggests that they are capable of utilizing multi-carbon compounds. Thus, the substrate range might be important ecological niche-defining factors for methylotrophs to survive in a complex microbial community of topsoils. The project aimed for the extension of our knowledge of trophic strategies of methylotrophs, which utilize one-carbon VOCs, and thrive at energetic limits in globally important one-carbon compound sinks. Such a sink. i.e. forest soil, being one of strongest methane sinks on global scale, were chosen for the project’s investigations. The site is named Steigerwald and is located on North Bavaria (Germany). The hypothesis investigated experimentally in the project was: Utilization of plant-derived alternative substrates is a key trophic strategy of ambient methane-, methanol-, and chloromethane-utilizing methylotrophs in forest soils. A major result of our project was that activity and growth of methanotrophs that consumed even atmospheric methane concentrations in the investigated topsoil were not induced by the supplementation of potentially alternative multi-carbon growth substrates. This unexpected result, however, was in accordance with another major finding that only few multi-carbon compounds were consumed by active bacterial methanol utilizers in the same soil. However, our project nicely demonstrated that soil sink activities for chloromethane and methanol are functionally and on organismic level linked. Thus, plant- and organic materialreleased methanol also facilitates the chloromethane degradation in forest soil. Taken our observations together, it is likely that multi-carbon compounds are only of minor importance for the trophic ecological niche of forest soil methylotrophs. An interesting future route of research would be to test further substrates, e.g. molecular hydrogen or carbon monooxide since recent studies suggest that in particular soil and sediment methanotrophs may utilize these compounds. We are also convinced that typical methanotrophs in forest soils do not utilize in situ alternative multi-carbon compounds to methane as growth substrates. This conclusion is agreement with previous studies that demonstrated that only under artificially high concentration acetate may be assimilated.
Publications
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Bacteria as chloromethane sinks – from model strains to forest soil communities. (2016) Dissertation at Faculty of Biology, Chemistry and Geo Sciences at the University of Bayreuth; the School of Natural Sciences of the University of Strasbourg (France)
Chaignaud, Pauline
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(2017) Acidotolerant Bacteria and fungi as a sink of methanol-derived carbon in a deciduous forest soil. Frontiers in Microbiology 8, Article 1361
Morawe, M., Hoeke, H., Wissenbach, D., Lentendu, G., Wubet, T., Kröber, E., Kolb, S.
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(2017) Genomic and transcriptomic analysis of growthsupporting dehalogenation of chlorinated methanes in Methylobacterium. Frontiers in Microbiology 8, Article 1600
Chaignaud, P., Maucourt, B., Weiman, M., Alberti, A., Kolb, S., Cruveillier, S., Vuilleumier, S., Bringel, F.
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Aerobic Methylotrophic Microorganisms in an Acidic Deciduous Forest Soil: Substrate Range and Effect of pH. (2017). Dissertation at Faculty of Biology, Chemistry and Geo Sciences at the University of Bayreuth
Morawe, Mareen
