What is it about?

There has always been a clear distinction between methanotrophs and sulfur oxidizers. Their unique choice of growth substrate is well established, so obtaining a bacterium, Methylovirgula thiovorans strain HY1, that combines both forms of metabolism and bridges the gap between these functional microorganisms is unique. Strain HY1 is a facultative bacterium that can conserve energy by oxidizing methane or sulfur either in concert or singly.

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Why is it important?

Strain HY1 is the first bacterium demonstrating that methanotrophy and thiotrophy are compatible in a single microorganism, and this greatly expands the current concept of facultative methanotrophy. Such mixotrophic methane/sulfur-oxidizing bacteria may underpin the intimate interactions of methane and sulfur cycles in oxic–anoxic interface environments. A strong sulfur cycle can inhibit methane production and when such a situation arises, strain HY1 growth can be fueled by sulfur and thus, help replenish the sulfate pool and also sustain sulfate reduction in wetlands. Additionally, our study highlights the difficulties in inferring methanotrophy and thiotrophy based on 16S rRNA phylogeny. Due to a possible combination of methanotrophy with other metabolisms, undiscovered metabolic versatility like that found in strain HY1 may be ubiquitous in nature.


There are several questions yet unanswered that require future studies. Studies on the regulation, kinetics, and evolution of thiotrophic and methanotrophic metabolisms in this strain are required. Also, 16S rRNA phylogeny cannot fully resolve microbial functions, hence, further investigative studies on microorganisms in the same clade with strain HY1 and their functions need to be resolved. We assume that there remain unexplored methanotrophs with thiotrophy. How abundant are methanotrophs with thiotrophy in environments and how important are they in mitigating methane emission? I guess we are bound for surprises.

Sung Keun Rhee
Chungbuk National University

Read the Original

This page is a summary of: Sulfur and methane oxidation by a single microorganism, Proceedings of the National Academy of Sciences, August 2022, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2114799119.
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