Streptococcus thermophilus Genome sequencing. Streptococcus thermophilus

Streptococcus thermophilus, a bacterium from dairy products, is an aerobic Gram-positive bacterium, non-budding, non-motile, typically round or oval, arranged in pairs or chains, with an optimum fermentation pH of 6.0-7.0 and an optimum growth temperature of 35-45 degrees centigrade. It belongs to the thermophilic group of lactic acid bacteria. Streptococcus thermophilus has become the only strain of the genus Streptococcus to be certified as GRAS (Commonly Recognized as Safe, GRAS) by the European Union due to the decline of its virulence genes from its lengthy residence in the dairy environment. It is widely used in the production of a number of vital fermented dairy products, including yoghurt and cheese. The genome of Streptococcus thermophilus has a genome size of about 1.8 Mb, a relatively low GC content of about 39%, and codes for 2,938 genes containing about 100 pseudogenes. Streptococcus thermophilus has undergone a great deal of gene level transfer and gene decline during its evolution, mainly focusing on the sugar metabolism and protein transport systems, i.e. certain genes involved in sugar metabolism and certain pathogenicity genes were gradually transformed into pseudogenes or disappeared from the genome, while genes encoding related functional proteins, such as bacteriocins, extracellular proteases and extracellular polysaccharides, were also acquired. No genes encoding virulence traits or virulence factors were found and no progenitors were identified. The chromosomes contained insertion sequence (IS) elements. The absence of antibiotic resistance and troubling genes in this bacterium suggests that Streptococcus thermophilus is safe. As such, the strain can be used as a starter or as a probiotic in the fermentation of dairy products and other foods. And the use of its bacterial preparations in the development of modern alternative food products or as probiotics. In this study, we want to explore the ability of Streptococcus thermophilus to produce different metabolites than just the amount of lactic acid produced by its fermentation.