Friendly Microbes Break Down Chemicals in Riverbed Gravel and Sand

Jenn Hoskins
21st July, 2024

Friendly Microbes Break Down Chemicals in Riverbed Gravel and Sand

The addition of dimethylsulfide (DMS) to river sediments caused Methanomethylovorans to become the dominant methanogen genus (a), resulting in a significant community shift (b) and a substantial increase in the total methanogen population (c), thereby establishing its key role in DMS-dependent methane production.

Image adapted from: Tsola et al. / CC BY (Source)

Key Findings

  • Researchers at Queen Mary University of London studied methane production in river sediments using dimethylsulfide (DMS) as a substrate
  • Sandy river sediments produced significantly more methane from DMS than gravel sediments
  • Methanomethylovorans were identified as the dominant methanogens responsible for DMS-dependent methane production in all river sediments tested
Rivers and streams are crucial elements of the global carbon cycle and methane budget. However, the microbial diversity and metabolic pathways that drive methylotrophic methane production in river sediments remain poorly understood. Dimethylsulfide (DMS), a significant methylated compound found in freshwater sediments, plays a role in these processes, yet the extent of DMS-dependent methanogenesis and the specific methanogens involved in river sediments have not been previously explored. Researchers at Queen Mary University of London aimed to address this knowledge gap in their recent study[1]. The study focused on DMS-dependent methanogenesis in gravel and sandy river sediments. Methanogenesis is the production of methane by microorganisms, specifically methanogens, which are a group of archaea. DMS-dependent methanogenesis involves the use of DMS as a substrate by methanogens to produce methane. This process is important because methane is a potent greenhouse gas, and understanding its production in river sediments can help refine global methane budgets. Previous studies have highlighted the significance of rivers and streams in the biogeochemical exchange with the atmosphere, particularly in the context of carbon dioxide fluxes[2]. However, methane production in these environments has received less attention. The study at Queen Mary University of London builds on this foundation by exploring the microbial processes underlying methane production in river sediments. The researchers collected sediment samples from various river sites and conducted incubation experiments to measure methane production. They used DNA sequencing techniques to identify the methanogenic archaea present in the samples and to determine their metabolic pathways. The study revealed that DMS is a significant substrate for methanogenesis in river sediments, with certain methanogens being highly active in this process. This finding aligns with earlier research that identified methanogens in upland soils, including dryland soils, where Methanosarcina and Methanocella were found to be dominant[3]. These methanogens were shown to produce methane rapidly under anoxic conditions, which supports the idea that specific methanogens are well-adapted to their environments and play a crucial role in methane production. In addition to Methanosarcina and Methanocella, the study also identified other methanogens capable of utilizing DMS as a substrate. This expands the known diversity of methanogens involved in methylotrophic methanogenesis. The study's findings are further supported by research on Methanomethylovorans, a genus of methanogens that can use methylated compounds like DMS for methane production[4]. The presence of such methanogens in river sediments suggests that they may have a broader ecological role than previously thought. Furthermore, the study's use of DNA sequencing and stable isotope probing techniques to identify DMS-degrading microbial communities in terrestrial environments provides additional context. Previous research has shown that members of the Methylophilaceae family, which were not previously implicated in DMS degradation, play a key role in this process[5]. These findings highlight the importance of microbial diversity in DMS cycling and methane production across different ecosystems. By uncovering the role of DMS-dependent methanogenesis in river sediments, the study by Queen Mary University of London contributes to a more comprehensive understanding of the global methane budget. It highlights the need to consider the contributions of various methanogenic pathways and microbial communities in different environments. This knowledge can inform climate models and strategies to mitigate methane emissions, ultimately helping to address the challenges posed by climate change.

EnvironmentBiochemEcology

References

Main Study

1) Methanomethylovorans are the dominant dimethylsulfide-degrading methanogens in gravel and sandy river sediment microcosms

Published 20th July, 2024

https://doi.org/10.1186/s40793-024-00591-4

Related Studies

2) Global extent of rivers and streams.

https://doi.org/10.1126/science.aat0636

3) Methanogenic archaea are globally ubiquitous in aerated soils and become active under wet anoxic conditions.

https://doi.org/10.1038/ismej.2011.141

4) Methanomethylovorans uponensis sp. nov., a methylotrophic methanogen isolated from wetland sediment.

https://doi.org/10.1007/s10482-013-0020-4

5) SIP metagenomics identifies uncultivated Methylophilaceae as dimethylsulphide degrading bacteria in soil and lake sediment.

https://doi.org/10.1038/ismej.2015.37


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