DNA base composition and DNA-DNA homologies of methanol-utilizing bacteria.

Abstract

DNA base composition was determined in 73 strains of aerobic, gram negative, methanol-utilizing bacteria, which are divided into nine groups on the basis of chemotaxonomic characteristics and utilization of carbon compounds. Guanine plus cytosine (G + C) contents in their DNAs ranged from 50.0 to 68.8 mol% G + C. Group 1 bacteria (obligate methanol-utilizing bacteria) and group 4 bacteria (Hyphomicrobium strains) showed rather wide distributions in DNA base composition, 50.0 to 56.0 mol% G + C and 59.3 to 65.6 mol% G + C, respectively. In contrast, bacteria of group 2 (Protomonas strains), group 3 (Microcyclus strains), group 5 (Xanthobacter strains), group, group and group 8 (Paracoccus denitrificans strains) had narrow ranges in DNA base composition. Group 9 (Thiobacillus novellus) had 67.7 mol% G + C. DNA-DNA homologies among the strains selected from the above-mentioned groups indicated a clear separation of the group 1 from the other groups. Further, group 1 was divided into six subgroups but not enough phenotypic characteristics were found to separate them from each other. Therefore, despite the heterogeneity of group 1 suggested by DNA base composition, DNA-DNA homology relatedness, and other chemotaxonomic characteristics, this group of bacteria are considered to be a single species from the practical point of view.