Intra- and Intergeneric Similarities of the Ribosomal Ribonucleic Acid Cistrons of Acetobacter and Gluconobacter

Abstract

Hybrids between 14C-labeled ribosomal ribonucleic acid (rRNA) from either Gluconobacter oxydans subsp. oxydans NCIB 9013, Acetobacter aceti subsp. aceti NCIB 8621t1, or Zymomonas mobilis subsp. mobilis ATCC 29191 and deoxyribonucleic acid (DNA) from acetic acid bacteria and representative strains of possibly related and other gram-negative bacteria were prepared. Each hybrid was described by two parameters: Tm(e) , the temperature at which 50% of the hybrid was denatured, and the percentage of rRNA. binding, the amount of 14C-labeled rRNA (in micrograms) duplexed under stringent conditions per 100 µg of filter-fixed homologous or heterologous DNA. Each taxon occupied a definite area on the rRNA similarity maps. Parameters of hybrids formed with rRNA from G. oxydans subsp. oxydans NCIB 9013 showed that the acetic acid bacteria consist of two separate but closely related groups corresponding to the genera Acetobacter and Gluconobacter. When compared with rRNA from A. aceti subsp. aceti NCIB 8621t1, both genera were indistinguishable, showing that there were many strains of. Acetobacter whose rRNA cistrons are as different from the reference Acetobacter rRNA as from Gluconobacter rRNA. The rRNA cistrons of Acetobacter were more heterogeneous than these of Gluconobacter. The great similarities among the m(e) 's of the heterologous hybrids and among the numerous phenotypic features stress that both genera are more closely related to each other than to any other genus. The parameters of the DNA:rRNA hybrids located the acetic acid bacteria as a separate branch in an rRNA superfamily consisting of Rhodopseudomonas, Beijerinckia, Agrobacterium, Rhizobium, some Spirillum species, and Paracoccus denitrificans. Parameters of hybrids formed with rRNA from Z. mobilis subsp. mobilis ATCC 29191 showed that the genus Zymomonas forms a separate branch in the same rRNA superfamily. We detected a number of misnamed organisms. “Acetobacter” aceti subsp. xylinum NCIB 4112, “Acetobacter” aceti subsp. orleanensis NCIB 6426, and “Acetobacter” lermae NRRL B-1810 belong in the genus Gluconobacter. “Gluconobacter” industrius IFO 3261, “Gluconobacter” dioxyacetonicus IAM 1814, “Gluconobacter” sp. strains A4.1 and M28, “Pseudomonas” melophthora NCPPB 461 and 462, and “Pseudomonas” pomi NCPPB 463 are all regular members of Acetobacter. Our evidence is against the maintenance of “intermediate” strains of acetic acid bacteria. “Gluconobacter” liquefaciens NCIB 9505 and IAM 1834 and “G.” melanogenus IAM 1835 and IAM 1836 are genetically regular members of the genus Acetobacter. “Acetobacter” aurantius IFO 3246 is a Gluconobacter. “A.” aurantius IFO 3249, 3247, 13330, and 13333 are not acetic acid bacteria at all. We propose to unite Acetobacter and Gluconobacter in the family Acetobacteraceae. The ranges of the moles percent guanine plus cytosine of the DNAs have been determined for the different taxa in both genera.