Complete genome sequence of Streptococcus lingualis isolated from subgingival biofilm

Streptococcus lingualis is a recently described oral streptococcal species; however, genomic information for this species remains limited, with only a single complete genome currently available for the type strain S5ᵀ. The objective of this study was to generate a high-quality complete genome sequence of a subgingival biofilm-derived S. lingualis isolate and expand the genomic resources available for this species.

The S. lingualis strain KHUD_012 was isolated from subgingival biofilm of a healthy adult and sequenced using the PacBio Sequel IIe platform. A single SMRT cell produced 144,821 HiFi reads, which were assembled de novo using the IPA HiFi genome assembler v2.0. The complete genome consists of a single circular chromosome of 2,115,610 bp with a G + C content of 42.0%, encoding 1,956 protein-coding genes, four rRNA operons, and 62 tRNAs. BUSCO analysis indicated 99.5% completeness. Pairwise whole-genome comparisons with closely related type strains showed that KHUD_012 was most closely related to S. lingualis S5ᵀ, with an OrthoANI value of 96.44%, and Parsnp-based core-genome SNP analysis supported this phylogenetic placement. Comparative genomic analysis with S5ᵀ identified 1,717 shared core gene clusters and 198 unique gene clusters in KHUD_012, many of which were functionally uncharacterized.