Genome analysis of Streptococcus salivarius subsp. thermophilus type strain ATCC 19258 and its comparison to equivalent strain NCTC 12958

Streptococcus thermophilus is one of the lactic acid bacteria applied as the main starter for dairy foods. A type strain of Streptococcus salivarius subsp. thermophilus ATCC 19258 has been used in the genetic and biochemical characterization of their genes or gene products. While the genome sequence of NCTC 12958 as an equivalent to ATCC 19258 is available, characterization of whether both collections are identical remains to be validated. Here, we report the complete genome sequence of ATCC 19258, which contains one 2.1 Mb chromosome with a 39.0% of G + C content, and includes 2255 protein-coding sequences, 77 RNAs, 4 riboswitches, and 3 CRISPRs. The data were further compared with NCTC 12958 and found that 54 mutations and 4 gaps occurred in NCTC 12958, resulted in both the mutations and insertions of nucleotides in the genome. Unlike ATCC 19258, pre-termination of three genes encoding IS981 transposase B, MltF, and FetB were detected in NCTC 12958. Our study highlights that type strains of Streptococcus thermophilus in two available independent strain collections are possibly different and therefore, the functions of previously identified or hitherto uncharacterized genes of Streptococcus thermophilus should be carefully assigned based on the genomic database of the strain.

Automated summary

This study reports the complete genome sequence of Streptococcus thermophilus strain ATCC 19258, highlighting differences compared to strain NCTC 12958. The findings suggest caution should be taken when assigning functions to known or previously uncharacterized genes of Streptococcus thermophilus.