Page 265 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

throughput method (Callahan et al. 2019). In addition, the rpoB gene, which encodes the β subunit of the prokaryotic RNA polymerase, provides a promising alternative with finer taxonomic resolution (Ogier et al. 2019). A limitation of archaea-specific rpoB primers, however, highlights the biggest current caveat of its use for microbial diversity analysis (Dridi et al. 2009; Rastogi et al. 2009; Koskinen et al. 2017).
Metagenomics sequencing can resolve most issues, but costs, sequencing depth, and analyzing power provide important limitations. Furthermore, metagenomics studies cannot always provide the desired answers. Unraveling the role of changing temperatures on permafrost environments requires insights into effects on the transcriptome, proteome, and, especially, metabolome level, as shown in a recent study on Alaskan permafrost by Messan et al. (2020). Only then we can properly understand the microbes, and their mechanisms and responses to a changing environment. Integrating different datasets can, therefore, be important to explain the observed shifts in GHG fluxes.
The interaction of microorganisms ultimately determines methane fluxes into the atmosphere
The research presented in this thesis focused on unraveling controls of in situ methane cycles in a changing environment. Chapter 3 to 5 focused on the role and potential of methane cycling communities in organic-rich deposits. Here, we wanted to unravel the contribution of methane cycling microorganisms as well as the key factors controlling their occurrence and activity. Chapter 6 to 9 focused on the microbial controls of climate change in cold ecosystems. In this second part, we wanted to better understand both how microbes affect climate change, and how they will in turn be affected by climate change. It is, furthermore, important to realize that different species, and thus methanogens, methanotrophs and all other microbial guilds, respond differently to a changing climate. Therefore, an ecosystem response to climate change is dependent on a multitude of biotic and abiotic factors that together determine the ratio of CO2 and CH4 emissions, which in turn determines the climate impact of these emissions. Climate change is more than a linear consequence of a single cause and it requires holistic, multidisciplinary efforts to be both understood and resolved.
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