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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 <i>Methylococcus</i>-like Type Ib methanotroph recovered from an alkaline thermal spring (55.4 &#176;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 <i>Methylococcaceae</i> of the class <i>Gammaproteobacteria</i>. The 16S rRNA gene phylogeny indicated that strain LS7-MC is distantly related to the closest described relative, <i>Methylococcus capsulatus</i> (92.7% sequence identity). Growth was observed at temperatures of 30&#8722;60 &#176;C (optimal, 51&#8722;55 &#176;C), and the cells possessed Type I intracellular membrane (ICM). The comparison of the <i>pmoA</i> gene sequences showed that the strain was most closely related to <i>M.</i> <i>capsulatus</i> (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 <i>mxaF</i>, <i>cbbL</i> and <i>nifH</i> 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 <i>Methylococcaceae</i>. 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.