Subsurface microbes turn methoxy compounds in coal into methane

As long as people have been mining coal, they have had to be wary of methane that comes along with it—much to the detriment of canaries prior to the development of modern gas-detection methods. The source of the methane still remains something of a mystery: Scientists believe that methanogenic microbes play a large role, but it’s not clear which compounds serve as the raw material. For at least one strain of archaea, the answer appears to be methoxylated aromatic compounds derived from lignin, reports a team led by Yoichi Kamagata and Susumu Sakata of Japan’s National Institute of Advanced Industrial Science & Technology (Science 2016, DOI: 10.1126/science.aaf8821). The researchers found that a strain of Methermicoccus shengliensis produces methane in lab tests of more than 30 individual methoxylated compounds, as well as from coal itself. Unlike previously identified methanogenic pathways, the microbe appears to produce methane through demethylation of methoxy groups, somehow coupled to reduction of carbon dioxide and possibly involving acetyl coenzyme A as an intermediate. The microbes may also be producing methane in other subsurface sedimentary organic material, the researchers suggest.