Heterogeneity of strains assigned to Gluconobacter frateurii Mason and Claus 1989 based on restriction analysis of 16S-23S rDNA internal transcribed spacer regions

Twenty-three strains, which were assigned to Gluconobacter frateurii and maintained at Culture Collection NBRC, were re-identified at the species level on the basis of restriction analysis of 16S-23S rDNA ITS regions by digestion with six restriction endonucleases: Bsp1286I, MboII, AvaII, TaqI, BsoBI, and BstNI. The strains examined were divided into six groups, Group III-1, Group III-2, Group III-3, Group III-4, Group III-5, and Group IV. Group IIII-1 and Group III-4 respectively were divided into two subgroups, Subgroup III-1a, Subgroup III-1b and Subgroup III-4a, Subgroup III-4b. Gluconobacter frateurii NBRC 3264 T was included in Group III-2, along with strains NBRC 3265 and NBRC 3270, and G. thailandicus BCC 14116(T) was included in Group III-3, along with strains NBRC 3254, NBRC 3256, NBRC 3258, NBRC 3255, and NBRC 3257. These groupings were supported by a phylogenetic tree based on 16S-23S rDNA ITS sequences. Strains of group III-2 and Group IV were unequivocally re-identified as G. frateurii, but strains of Group III-3, Group III-4, and Group III-5 were not necessarily re-identified as G. frateurii. The results obtained indicate that the 23 strains have a taxonomically heterogeneous nature, and they are referred to as the G. frateurii complex.