Proposal of Lactococcus intestinalis Sun et al. 2024 as a Later Heterotypic Synonym of Lactococcus muris Afrizal et al. 2023.

Lactococcus muris was published in Cell Host & Microbe in November 2022 and validated in validation list no. 213 in October 2023. Lactococcus intestinalis was published in Antonie van Leeuwenhoek in May 2023 and validated in validation list no. 216 in March 2024. Both of them were isolated from the mouse gut. Previous studies indicated that L. muris DSM 109779 had the highest 16S rRNA gene sequence identity to Lactococcus garvieae (96.7%), and that L. intestinalis M2458 had the highest 16S rRNA gene sequence similarities to Lactococcus formosensis NBRC 109475 (97.6%) and L. garviae NBRC 100934 (97.1%). However, the taxonomic relationship between L. muris and L. intestinalis has not yet been investigated and therefore is the focus of the present study. In the present study, the relationship between L. muris and L. intestinalis was evaluated. The type strains of L. muris and L. intestinalis shared 100% 16S rRNA gene sequence similarity, 100% pheS sequence similarity, 100% rpoA sequence similarity, 99.9% average nucleotide identity (ANI) value and 98.5% digital DNA-DNA hybridization (dDDH) value, indicating that they represented the same species. On the basis of the results present here, we propose L. intestinalis Sun et al. 2024 as a later heterotypic synonym of L. muris Afrizal et al. 2023.