Characterization of a novel facultative Methylocystis species capable of growth on methane, acetate and ethanol

Summary A non-motile strain of Methylocystis, strain SB2, isolated from a spring bog in southeast Michigan, had a curved rod morphology with a typical type II intracytoplasmic membrane system. This organism expressed the membrane-bound or particulate methane monooxygenase (pMMO) as well as a chalkophore with high affinity for copper and did not express the cytoplasmic or soluble methane monooxygenase (sMMO). Strain SB2 was found to grow within the pH range of 6–9, with optimal growth at 6.8. Growth was observed at temperatures ranging between 10°C and 30°C, with no growth at 37°C. The DNA G+C content was 62.9 mol%. Predominant fatty acids were 18:1ω7c (72.7%) and 18:1ω9c (24%) when grown on methane. Phylogenetic comparisons based on both pmoA and 16S rRNA sequences indicated that this organism belonged to the Methylocystis genus, and was closely related to Methylocystis rosea SV97T and Methylocystis echinoides IMET10491T (98% 16S rRNA gene sequence similarity to both strains). DNA : DNA hybridizations indicated that strain SB2 had 70% similarity with M. rosea SV97T. Unlike M. rosea SV97T, strain SB2 was able to utilize not only methane for growth, but also ethanol and acetate. Furthermore, the predominant fatty acids in strain SB2 were different from those found in M. rosea SV97T, i.e. 54.2% and 39.7% of fatty acids are 18:1ω8 and 18:1ω7 in M. rosea SV97T, while 18:1ω8 is completely absent in strain SB2.