Pig gut mining yields Lactobacillus reuteri strain that eases colitis in mice

Scientists searching for new probiotics have long relied on a simple recipe: isolate microbes from a sample, test them one by one in the laboratory, and hope that something useful turns up. A team studying Tunchang pigs, an indigenous breed from Hainan Province in southeastern China, argues that this conventional isolate-and-screen approach often lacks ecological context, producing strains with uncertain safety profiles and unpredictable functional performance. Instead, the researchers turned the process around, starting from the ecology of the animals’ gut and working downward toward a specific bacterial candidate.

Indigenous pig breeds that thrive under low-input husbandry conditions are described in the study as underexplored living libraries, offering gut niches shaped by both host and environment. Tunchang pigs served as the model for this top-down, ecology-guided mining of host-derived probiotics from a native gut niche. By combining cross-sectional age-gradient metagenomics with cross-breed comparisons, the team defined a Tunchang-pig gut niche carrying a lower overall burden of annotated virulence factor and antimicrobial resistance gene features than that of Duroc × Landrace × Yorkshire commercial pigs.

Within this niche, Limosilactobacillus reuteri was consistently detected in a lactobacilli-enriched core microbiota across developmental-stage groups and showed limited associations with annotated virulence factor and antimicrobial resistance features at the community level. The niche was also associated with higher relative levels of several host–microbe co-metabolites, including indoleacrylic acid and N-decanoylglycine. These community-level features gave the researchers an ecological rationale for treating the Tunchang gut as a promising source of probiotic candidates rather than sampling microbes at random.

Guided by this framework, the team isolated a Tunchang pig-derived L. reuteri strain, designated TC-Lr, together with a co-isolated Lactobacillus johnsonii strain, TC-Lj. Targeted profiling of cell-free culture supernatants revealed a distinct tryptophan-associated metabolic profile for the two isolates. TC-Lr produced higher concentrations of indole-3-lactic acid and tryptophol than TC-Lj, a biochemical difference that would soon matter in animal testing.

To test functional performance, the researchers used a mouse model of colitis induced by dextran sulphate sodium, a chemical that damages the colon lining and triggers inflammation. In this model, TC-Lr, but not TC-Lj, alleviated weight loss and disease activity, attenuated colon shortening, and reduced inflammation-associated haematological alterations. The contrast between the two co-isolated strains suggests that even closely related lactobacilli from the same niche can differ sharply in their effects on gut inflammation.

TC-Lr also partially restored colonic metabolism that had been disrupted by the dextran sulphate sodium treatment. In treated mice, the strain increased adenosine while reducing creatinine and histamine levels in the colon. These metabolic shifts provide a measurable signature of how the bacterial strain interacted with the inflamed gut beyond the visible clinical signs such as weight loss and colon length.

The authors conclude that the findings support an ecology-guided, top-down framework for prioritising host-derived probiotics from indigenous livestock breeds. They further suggest that the Tunchang pig gut, characterised by a lactobacilli-enriched community and a lower annotated virulence factor and antimicrobial resistance burden at the community level, may serve as an ecological source for prioritising host-derived probiotic candidates. In practical terms, the breed’s native gut community acted as a filter that narrowed the search space before any single strain was cultured.

The work carries the usual caveats of early-stage probiotic research. The anti-colitis effects were demonstrated in a chemically induced mouse model, not in pigs or humans, and the published version notes that the article is being shared early as peer-reviewed, accepted research that remains subject to further edits before the final Version of Record. Mouse colitis models are widely used to screen candidate strains, but they do not by themselves establish efficacy in a clinical setting.

Even so, the study offers a concrete example of how ecological data can steer probiotic discovery. Rather than screening large libraries of unrelated isolates, the researchers used metagenomic comparisons between breeds and across age groups to identify a gut niche with favourable community-level features, then isolated strains from that niche and tested their metabolic outputs and functional effects. If the approach holds up in further studies, indigenous livestock breeds raised under low-input conditions could become a systematic starting point for finding host-derived bacterial strains with defined anti-inflammatory profiles.

Subject of Research: Ecology-guided mining of the Tunchang pig gut microbiome to identify a host-derived Limosilactobacillus reuteri strain with anti-colitis activity in a mouse model

Article Title: Top-down mining of a lactobacilli-enriched gut niche in Tunchang pigs identifies a host-derived Limosilactobacillus reuteri strain with anti-colitis activity

Article References: Lin, Z., Yang, Y., Chen, S., An, W., Zhang, L., & Han, X. (2026). Top-down mining of a lactobacilli-enriched gut niche in Tunchang pigs identifies a host-derived Limosilactobacillus reuteri strain with anti-colitis activity. Microbiome. https://doi.org/10.1186/s40168-026-02565-9

Image Credits: AI Generated

DOI: 10.1186/s40168-026-02565-9

Keywords: probiotics, Limosilactobacillus reuteri, Tunchang pigs, gut microbiome, colitis, metagenomics, indigenous pig breeds, DSS-induced colitis, tryptophan metabolites, host-derived strains, antimicrobial resistance genes, mouse model