METHYLOVORUS, A NEW GENUS OF RESTRICTED FACULTATIVELY METHYLOTROPHIC BACTERIA

A new genus, Methylovorus, and one new species are described for a group of restricted facultatively methylotrophic bacteria. Five strains belonging to the new genus are characterized by a low level (5 to 15%) of DNA-DNA homology with type strains of restricted facultative methylobacteria of the genus Methylophilus (M. methylotrophus NCIB 10515T) and obligate methylobacteria of the genus Methylobacillus (M. glycogenes ATCC 29475T). The Methylovorus strains, like Methylophilus and Methylobacillus strains, assimilate methanol via the ribulose monophosphate pathway and do not have alpha-ketoglutarate dehydrogenase and glyoxylate bypass enzymes. Methylovorus strains are characterized by an enhanced specificity of 6-phosphogluconate dehydrogenase to NAD (not NADP) the absence of glutamate dehydrogenase, and the presence of the glutamate cycle enzymes for ammonia assimilation. The deoxyribonucleic acid base composition of the Methylovorus strains is 56 to 57 mol% guanine plus cytosine. Their phospholipids are similar to those of Methylobacillus but differ from those of Methylophilus by the occurrence of diphosphatidylglycerol. The fatty acid composition of the strains of all three genera is primarily C16:1-omega-7 and C16:0, although the Methylophilus, but not Methylovorus, strains also contain two unidentified C17 branched fatty acids. The type species is Methylovorus glucosotrophus sp. nov. The type strain is 6B1 (= UCM B-1475).