Ribosomal ribonucleic acid cistron homologies among Hyphomicrobium and various other bacteria.

The extent of hybrid formation between the ribosomal ribonucleic acid (r-RNA) of Hyphomicrobium strain B-522 and deoxyribonucleic acid (DNA) from bacteria of 21 different genera was examined. Three generalized groupings were formed. Group I (72-100%) consisted entirely of other strains of Hyphomicrobium. Representatives of the genera Rhodopseudomonas, Chromatium, Caulobacter, Prosthecomicrobium, Rhodomicrobium, Hyphomonas, and Hyphomicrobium made up group II (49-69%). The remaining Gram-negative, Gram-positive, and cell wall--less bacteria fell into group III (12-40%). The taxonomic implications of these results are discussed.