Genomics landscape of 185 Streptococcus thermophilus and identification of fermentation biomarkers.

Streptococcus (S.) thermophilus, an indispensable dairy starter, has been used in autochthonous as well as industrial milk fermentation. However, the genetic architecture underlying S. thermophilus traits and phenotypes is largely unknown. Here, we sequenced 185 S. thermophilus strains, isolated from natural fermented dairy products of China and Mongolia and used comparative genomic and genome wide association study to provide novel point for genetic architecture underlying its traits and phenotypes. Genome analysis of S. thermophilus showed association of phylogeny with environmental and phenotypic features and revealed clades with high acid production potential or with substantial genome decay. A few S. thermophilus isolated from areas with high chloramphenicol emissions had a chloramphenicol-resistant gene CatB8. Most importantly, we defined a growth score and identified a missense mutation G1118698T located at the gene AcnA that were both predictive of acidification capability of S. thermophilus. Our findings provide novel insight in S. thermophilus genetic traits, antibiotic resistant and predictive of acidification capability which both may had huge help in culture starter screening.