The impact of Streptococcus thermophilus IDCC 2201 on gut microbiota and its potential as a prophylactic agent for colorectal cancer.

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths. The gut microbiota is known to be closely associated with CRC development, interacting with each other and influencing host metabolism. Probiotic interventions have been applied to prevent CRC; however, the mechanisms underlying their effects on CRC remain unclear. In this study, we evaluated the effects of the probiotic strain Streptococcus thermophilus IDCC 2201 on its interactions with gut commensal bacteria and CRC cell viability. S. thermophilus inhibited the growth of most bacterial species comprising the human gut microbiota, with the exception of Bacteroides dorei. Further studies identified several factors produced by S. thermophilus, such as xylan-degrading enzymes and B vitamins, which promoted B. dorei growth through nutrient cross-feeding. During co-culture of S. thermophilus with individual gut commensals, bioactive compounds such as folate were significantly produced, further inhibiting CRC cell viability along with the culture supernatant of S. thermophilus. These findings suggest that S. thermophilus IDCC 2201 may serve as a potential prophylactic agent for colon cancer, with its effects mediated through interactions with gut commensal bacteria.