Researchers at the Max Planck Institute for Marine Microbiology have overturned previous beliefs about the methanogen Methanothermococcus thermolithotrophicus, which was thought unable to convert sulfate into sulfide due to high energy costs and toxic byproducts. They discovered that this microbe can indeed grow on sulfate, identifying five crucial genes associated with sulfate-reduction enzymes in its genome, thus assembling the first sulfate assimilation pathway found in a methanogen. This finding holds significant implications for safer, more cost-effective biogas production through potential genetic engineering.
Sulfur is vital for synthesizing cellular materials, typically acquired by autotrophs like plants. Methanogens, which contribute to global methane production, were assumed to rely on alternative sulfur forms like sulfide due to energy limitations. The researchers demonstrated that M. thermolithotrophicus can efficiently use sulfate as its sulfur source, showcasing an innovative adaptation that involves modifying dissimilatory sulfate-reducing enzymes for assimilatory use. This discovery also paves the way for biotechnological advancements, eliminating the need for hazardous hydrogen sulfide in methanogen cultivation and facilitating the conversion of CO2 into methane biofuel. Further field studies are planned to understand the natural expression of these pathways.
