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.

Lactobacillus salivarius Rogosa et al. 1953 was described as a homofermentative lactobacillus with two varieties: salivarius, typified inter alia by the ability to ferment rhamnose, and salicinius, characterized by the ability to ferment the glucoside salicin. These varieties have become accepted as subspecies divisions. We have examined the relatedness of 32 L. salivarius strains by a polyphasic approach. Carbohydrate fermentation profile analysis did not support clear distinction of the two subspecies. L. salivarius UCC118 was shown to be facultatively heterofermentative, confirming in silico genome analysis. 16S rRNA gene sequences and 16S-23S rRNA intergenic spacer region sequences provided no discrimination between any of the strains or subspecies. Broad subdivisions were distinguishable by pulsed-field gel genomic digest patterns, but they did not allow subspecific or phenotypic distinctions. A phylogeny based upon groEL gene sequences was discordant with rhamnose or salicin fermentation data for many taxa, and no reliable phenotypic correlations could be established. In the absence of meaningful taxonomic criteria, we therefore propose that Lactobacillus salivarius comprises a single species with no infraspecific taxa. Based on the present study and literature data, an emended description of the species Lactobacillus salivarius is provided.

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