Hydrogen sulfide (H₂S) can be produced from the metabolism of foods containing sulfur in the gastrointestinal tract (GIT). At low doses, H₂S regulates the gut microbial community and supports GIT health, but depending on dose, age, and individual health conditions, it may also contribute to inflammatory responses and gut barrier dysfunction. Controlling H₂S production in the GIT is important for maintaining a healthy gut microbiome. However, research on this subject is limited due to the gaseous nature of the chemical and the difficulty of accessing the GIT in situ. In the present ex vivo experiment, we used a single-dose sodium sulfide preparation (SSP) as a H₂S precursor to test the effect of H₂S on the human gut microbiome across different age groups, including breastfed infants, toddlers, adults, and older adults. Metagenomic sequencing and metabolite measurements revealed that the development of the gut microbial community and the production of short-chain fatty-acids (SCFAs) were age-dependent; that the infant and the older adult groups were more sensitive to SSP exposure; that exogeneous SSP suppressed SCFA production across all age groups, except for butyrate in the older adult group, suggesting that H₂S selectively favors specific gut microbial processes.

Perfluorooctanoic acid (PFOA) is an environmentally persistent chemical that enters the gastrointestinal tract (GIT) via the food chain, posing a harmful, long-term threat to human health. In response to this challenge, research on the PFOA-GIT interaction is thriving. Currently, studies on the effect of PFOA on the epithelial cells of the GIT and those on its influence on the microbial community are often implemented separately, and less attention has been paid to the combinational effects of the chemical, the gut microbiome and metabolome. In the present study, we co-cultured fecal samples from healthy adults aged 25–70 in the ex vivo SIFR^® simulator, adding PFOA at 10 mg/L to represent the accumulated effects of long-term exposure. The results obtained from bacterial cell counting by flow cytometry and shotgun metagenomic sequencing revealed that PFOA was broadly disruptive to the microbiome and that Pseudomonadota emerged as the dominant phylum by replacing Bacteriodota and Bacillota, including key members of short-chain fatty acid-producing groups. Bacterial culture media with and without PFOA were collected and used in human colonoid cell culture for TEER and transcription measurement. It was shown that the PFOA-impacted microbial culture had stronger effects on the cell’s protective functions, in terms of tissue junction tightening, mucin biosynthesis, and immune response, than either untreated bacterial culture or PFOA alone. The results point out the possibility that the combination of PFOA and PFOA-impacted bacterial metabolites more strongly induces a change in epithelial cells’ protective function than either one alone.