A Novel Moderately Thermophilic Type Ib Methanotroph Isolated from an Alkaline Thermal Spring in the Ethiopian Rift Valley.

Aerobic moderately thermophilic and thermophilic methane-oxidizing bacteria make a substantial contribution in the control of global warming through biological reduction of methane emissions and have a unique capability of utilizing methane as their sole carbon and energy source. Here, we report a novel moderately thermophilic -like Type Ib methanotroph recovered from an alkaline thermal spring (55.4 °C and pH 8.82) in the Ethiopian Rift Valley. The isolate, designated LS7-MC, most probably represents a novel species of a new genus in the family of the class . The 16S rRNA gene phylogeny indicated that strain LS7-MC is distantly related to the closest described relative, (92.7% sequence identity). Growth was observed at temperatures of 30-60 °C (optimal, 51-55 °C), and the cells possessed Type I intracellular membrane (ICM). The comparison of the gene sequences showed that the strain was most closely related to (87.8%). Soluble methane monooxygenase (sMMO) was not detected, signifying the biological oxidation process from methane to methanol by the particulate methane monooxygenase (pMMO). The other functional genes , and were detected by PCR. To our knowledge, the new strain is the first isolated moderately thermophilic methanotroph from an alkaline thermal spring of the family . Furthermore, LS7-MC represents a previously unrecognized biological methane sink in thermal habitats, expanding our knowledge of its ecological role in methane cycling and aerobic methanotrophy.