This paper describes a new bacterial species, Acetobacter methanolicus, isolated from sludge and a methanol yeast fermentation process. The strains are gram-negative, facultatively methylotrophic, aerobic rods that grow optimally at pH 4.0-4.5 and 30-32°C. Unlike other Acetobacter species, A. methanolicus grows well on methanol, glucose, gluconate, 2,3-butanediol, and caproic acid as sole carbon sources. The bacteria oxidize methanol via the hexulose phosphate pathway and require either yeast extract or pantothenic acid as growth factors. Ethanol is oxidized to acetic acid only at concentrations below 0.5%, and lactate is oxidized very weakly but not used for growth. The DNA base composition is 62.3 mol% G+C. Through extensive phenotypic testing of 140 characteristics and DNA-rRNA hybridization, the authors demonstrate that A. methanolicus is genetically and biochemically distinct from A. pasteurianus and other known Acetobacter species, warranting recognition as a separate species within the genus.

Key findings

• A. methanolicus is a new acidophilic, facultatively methylotrophic Acetobacter species that can grow on methanol as a sole carbon and energy source via the hexulose phosphate pathway
• The strain grows optimally at pH 4.0-4.5 and temperature 30-32°C, with good growth on methanol, glucose, gluconate, caproic acid, and 2,3-butanediol as carbon sources
• A. methanolicus differs from A. pasteurianus by oxidizing ethanol only at concentrations below 0.5%, lacking lactate utilization for growth, and containing Q10 rather than Q9 as the major ubiquinone
• The species requires pantothenic acid or yeast extract as growth factors and has a DNA G+C content of 62.3 mol%
• Biochemical analysis reveals methanol assimilation occurs via the fructose biphosphate variant of the hexulose phosphate pathway, requiring phosphofructokinase enzyme activity