The name Lactobacillus cellobiosus is validly published, but the species is often neglected in taxonomic studies, due to its high similarity to Lactobacillus fermentum. In the present paper, literature data concerning the two species were reviewed. Phylogenetic placement of L. cellobiosus was obtained based on 16S rDNA sequences, and genetic similarity was further investigated by comparing partial recA gene sequences for the type strains of L. cellobiosus and L. fermentum. Based on the high identity values for 16S rDNA (99 %) and recA gene (98 %) sequences, the results of DNA-DNA hybridization assays and phenotypic traits available from the literature, it is proposed that L. cellobiosus be reclassified and, as a rule of priority, renamed as L. fermentum, the first described species.

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.

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