Strain R0052, isolated from a North American dairy starter culture, was initially identified as Lactobacillus acidophilus based on phenotypic analyses. However, upon sequencing the 16S rRNA gene, it became clear that the isolate was very highly related to Lactobacillus suntoryeus, Lactobacillus helveticus and Lactobacillus gallinarum, as similarities ranging from 99.3 to 99.8 % were observed. As an initial screening test to investigate the relatedness of strain R0052 and reference strains of L. suntoryeus, L. helveticus and L. gallinarum, the partial sequences for the genes encoding the alpha subunit of ATP synthase (atpA), RNA polymerase alpha subunit (rpoA), phenylalanyl-tRNA synthase alpha subunit (pheS), the translational elongation factor Tu (tuf), a surface-layer protein (slp) and the Hsp60 chaperonins (groEL) were determined and they revealed high relatedness between all of the strains. The determination of the 16S-23S rRNA internally transcribed spacer (ITS) sequences revealed 98.3-100% similarity between L. suntoryeus and L. helveticus strains. SDS-PAGE of whole-cell proteins did not distinguish between these species. Fluorescent amplified fragment length polymorphism (FAFLP) could distinguish between these taxa, but they still constituted a single cluster within the L. acidophilus group. Finally, DNA-DNA hybridization experiments between strain R0052 and the type strains of L. helveticus and L. suntoryeus yielded reassociation values above 70% and confirmed that these names are synonyms.

Eleven strains of a hitherto undescribed Gram-positive, catalase-negative, facultatively anaerobic rod-shaped bacterium from human sources and medical care products were characterized by phenotypic and molecular taxonomic methods. The phenotypic properties of the bacterium were consistent with its assignment to the genus Lactobacillus but it was readily distinguished from all currently described species of this genus by its biochemical characteristics and by SDS-PAGE analysis of its cellular proteins. Comparative 16S rRNA gene sequence analysis demonstrated that the unknown bacterium was a member of rRNA group I Lactobacillus which includes Lactobacillus delbrueckii, the type species of the genus, and close relatives. Lactobacillus gasseri and Lactobacillus johnsonii were the nearest phylogenetic relatives of the unknown bacterium, but 16S rRNA sequence divergence values of > 4% clearly showed that it represents a distinct species. Based on both phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium should be classified in the genus Lactobacillus, as Lactobacillus iners sp. nov. The type strain of Lactobacillus iners is CCUG 28746T.

Eight strains of Lactobacillus with identical partial 16S rRNA gene sequences and similar randomly amplified polymorphic DNA patterns were isolated from fermentation samples from Japanese and Scottish malt whisky distilleries. Phylogenetic analysis of almost complete 16S rRNA gene sequences from three representative strains (two from Japan, one from Scotland) placed them in the genus Lactobacillus as members of the Lactobacillus acidophilus group. Lactobacillus helveticus and Lactobacillus gallinarum were the most closely related species, with 16S rRNA gene similarities of 99.3 and 98.1 %, respectively. A similar phylogeny was derived from partial sequences of elongation factor Tu (tuf) genes in which the alleles from the three distillery isolates were identical and shared 99.0 % similarity with L. helveticus and L. gallinarum tuf genes. S-layer (slp) gene sequences suggested different relationships among the strains and the distillery isolates no longer formed a monophyletic group. The alleles from the Japanese and Scottish strains shared only 54 % similarity. Chromosomal DNA from the distillery strains gave DNA-DNA hybridization values between 79 and 100 % but showed less than 43 and 22 % reassociation with L. helveticus and L. gallinarum DNA, respectively. The name Lactobacillus suntoryeus sp. nov. is proposed for this novel taxon; the type strain is strain SAT (=LMG 22464T=NCIMB 14005T).