Genome-based reclassification of the genus Lactococcus and two novel species Pseudolactococcus yaeyamensis gen. nov., sp. nov. and Lactovum odontotermitis sp. nov. isolated from the gut of termites.

Abstract

The genus Lactococcus was proposed by Schleifer et al. by separating Lactococcus lactis from the genus Streptococcus. Although the family Streptococcaceae consists of four genera, each genus contains a relatively small number of species, with the exception of the genus Streptococcus, which contains more than 100 species. The genera Lactococcus and Lactovum currently comprise 26 species and a single species, respectively. This study evaluated the taxonomy of the genus Lactococcus based on the 16S rRNA gene phylogeny, core-genome phylogeny and (conserved) pairwise average amino acid identity. These evaluations clearly indicated that the genus Lactococcus could be divided into two genus-level clusters, and we propose to reclassify this genus into two; the authentic Lactococcus, which includes the L. lactis group, and a novel genus for which the name Pseudolactococcus is proposed. Three lactic acid bacterial strains, RyT2^T, OfM1^T and OfM2, were isolated from the gut of termites in Okinawa, Japan. Based on the combination of genetic and phenotypic data, we conclude that these isolates represent two novel species of the genera Pseudolactococcus and Lactovum, respectively, for which we propose the names Pseudolactococcus yaeyamensis sp. nov. (RyT2^T=JCM 36015^T=DSM 118067^T) and Lactovum odontotermitis sp. nov. (OfM1^T=JCM 34431^T=DSM 118066^T, OfM2=JCM 34432), respectively.