Expanding the verrucomicrobial methanotrophic world: Draft genomes of two novel species of Methylacidimicrobium gen. nov.

Methanotrophic Verrucomicrobia have been found in geothermal environments characterized by high temperatures and low pH values. We have isolated and characterized two new species of mesophilic acidophilic verrucomicrobial methanotrophs from a volcanic soil in Italy. On basis of their 16S rRNA phylogeny we proposed the new genus Methylacidimicrobium. The draft genomes of Methylacidimicrobium tartarophylax 4AC (2.75 Mb) and Methylacidimicrobium cyclopophantes 3B (2.44 Mb) have a GC content of 60.9% and encode for 2,804 and 2,511 ORFs, respectively. The metabolic machinery was similar to that seen with thermophilic verucomicrobial methanotrophs (genus Methylacidiphilum). The two genomes show only one complete pmoCAB operon but two different xoxF genes encoding the XoxF-type lanthanide-dependent methanol dehydrogenases. The latter genes possess the typical coordination-specific aspartate located two amino acids downstream of the catalytic aspartate. In addition all genes involved in the Calvin cycle, including the two subunits of the key enzyme RuBisCO, were present.