Taxonomic Studies on Some Gram-negative Methylotrophic Bacteria

One hundred and fifteen cultures, including obligate, restricted facultative and facultative methylotrophs and members of possibly related taxa, were tested for 135 characters based on morphology, physiology and biochemistry and the results were subjected to computer analysis. The polar lipid composition of all the strains was examined. The isoprenoid quinone composition and the mol% G + C value of the DNA were determined for all the obligate and restricted facultative bacteria, and also for some of the other strains representative of the clusters formed in the numerical taxonomic study. The results indicate that the obligate methanol-utilizing bacteria all exhibit a high phenotypic similarity and are taxonomically distinct from the restricted facultative and the facultative methanol-utilizing bacteria examined and from the pseudomonad reference strains. The results also indicate that the obligate methylotrophs and the restricted facultative methylotrophs represent two distinct taxa of generic status: Methylobacillus and a taxon which can be equated with the organisms currently referred to as ‘Methylophilus’.