This study used 5S ribosomal RNA sequencing to examine the taxonomic relationships among bacteria in the genera Acidomonas, Acetobacter, and Gluconobacter. Researchers isolated and sequenced 5S rRNA from 12 bacterial strains and constructed phylogenetic dendrograms using mutation distance analysis. The results revealed three distinct clusters: methylotrophic Acetobacter strains grouped with Acidomonas methanolica, non-methylotrophic Acetobacter species clustered separately, and Gluconobacter formed its own group. Notably, non-methylotrophic Acetobacter strains were phylogenetically closer to Gluconobacter than to methylotrophic Acetobacter strains. These molecular findings provide strong support for a previous proposal to reclassify methylotrophic Acetobacter strains into the separate genus Acidomonas based on their ability to utilize one-carbon compounds. While chemotaxonomic features like fatty acid and ubiquinone composition showed overlapping values between genera, 5S rRNA sequence data clearly demonstrated that methylotrophy is a valid characteristic distinguishing Acidomonas from Acetobacter. The three genera represent a single line of descent and should be classified within the family Acetobacteriaceae.

Key findings

• 5S rRNA sequencing revealed three distinct phylogenetic clusters: methylotrophic Acetobacter/Acidomonas methanolica, non-methylotrophic Acetobacter, and Gluconobacter
• Non-methylotrophic Acetobacter species are phylogenetically closer to Gluconobacter than to methylotrophic Acetobacter strains
• Molecular data strongly support reclassifying methylotrophic Acetobacter strains as the genus Acidomonas based on their methylotrophic capability
• The ability to utilize one-carbon compounds (methylotrophy) is the key distinguishing phenotypic feature between Acidomonas and Acetobacter
• Acetobacter, Gluconobacter, and Acidomonas form a single line of descent and should be classified together in the family Acetobacteriaceae