# Folate Production by Streptococcus thermophilus IDCC 2201 and Its Impact on Human Gut Microbiota

## TL;DR

This study shows that a probiotic strain, Streptococcus thermophilus IDCC 2201, produces folate, which supports the growth of specific gut bacteria, influencing gut microbiota balance.

## Contribution

The study identifies S. thermophilus IDCC 2201 as a major folate producer and demonstrates its impact on gut microbial growth through nutrient cross-feeding.

## Key findings

- Bacteroides thetaiotaomicron, Veillonella parvula, and Ruminococcus faecis showed 2.8- to 3.9-fold growth increases in the presence of folate.
- Co-culturing with S. thermophilus led to 1.2- to 1.9-fold higher growth of these bacteria compared to other species.
- Folate production by S. thermophilus influences gut microbiota balance through nutrient cross-feeding.

## Abstract

Probiotics have been extensively investigated as potential food supplements for human health benefits. Metabolites derived from probiotics are the primary factors that characterize each strain’s functionality and play a crucial role in shaping their effects on the human host. In this study, we characterized the secreted metabolite profiles of sixteen commercial probiotic strains and identified Streptococcus thermophilus IDCC 2201 as a major folate producer. To investigate its effects on gut microbiota, S. thermophilus was co-cultured with individual species comprising the human gut microbial community. Specific bacteria, such as Bacteroides thetaiotaomicron, Veilonella parvula, and Ruminococcus faecis, grew dependently on both folate and S. thermophilus. These bacteria exhibited greater growth in the presence of folate than in its absence, with 2.8-, 3.6-, and 3.9-fold increases, respectively. Additionally, they showed relatively higher growth when co-cultured with S. thermophilus compared to other bacterial species, with 1.2-, 1.3-, and 1.9-fold increases, respectively. Our results indicate that the interaction between probiotics and the human gut microbiota can influence changes in ecological balance through nutrient cross-feeding, and understanding this interaction can be applied to precision probiotic therapies.