A gram-positive, facultatively anaerobic, and coccoid or ovoid-shaped bacterium designated M2458T was isolated from the intestinal contents of APPswe/PSΔE9 mouse model of Alzheimer's disease. With the polyphasic approach, the taxonomic position of the novel isolate was confirmed. Strain M2458T grew well at 37 °C on YCFA agar. Strain M2458T belongs to the family Streptococcaceae and class Bacilli, and it is closed to Lactococcus formosensis NBRC 109475T (97.59% sequence similarity) according to its 16S rRNA gene sequence. In a comparison of two housekeeping genes, rpoA and rpoB, strain M2458T was found to be well separated from Lactococcus formosensis NBRC 109475T. On the basis of whole genome sequences, the DNA G+C content was 38.29 mol%. The phylogentic analysis of the whole genome showed that a different branch was clearly formed in the phylogenetic tree of strain M2458T compared to other strains in the genus Lactococcus. A total of eight genes in strain M2458T are involved in the 'neurodegenerative disease' pathway, which involves an annotated protein (glyceraldehyde 3-phosphate dehydrogenase) involved in Alzheimer's disease. In terms of average nucleotide identity and digital DNA-DNA hybridization, strain M2458T was identified as a novel species of the genus Lacococcus. The major fatty acids (> 10% of the total fatty acids) were C18:1ω9c (39.68%), C16:0 (13.26%) and C18:1ω7c (11.52%). The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and an unidentified phospholipid. As a result of its genotypic and phenotypic characteristics, strain M2458T was considered to be a new species within the genus Lactococcus; the name Lactococcus intestinalis sp. nov. has been proposed, with type strain M2458T (=JCM 35706 = CGMCC 1.60066).
Keywords: Alzheimer’s disease mice; Genomic characterisations; Lactococcus intestinalis sp. nov.; Polyphasic taxonomy.
© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.