Bacteroides thetaiotaomicron in Gut Homeostasis: Genomic Adaptation, Metabolic Function, and Immune Modulation

Abstract

Bacteroides thetaiotaomicron, a member of the gut commensal flora, is highly versatile and an important part of gut homeostasis in humans. Despite growing interest in its diverse biological functions, no previous review has comprehensively integrated its established roles in gut homeostasis with its emerging implications for gut–brain axis signaling, cancer immunomodulation, and future microbiome-based therapeutics. This review will fill this gap by offering an integrated and mechanistic review of these mutually connected functions. Specifically, this review focuses on the core biological functions of B. thetaiotaomicron, including genomic adaptation and regulatory plasticity, polysaccharide metabolism, nutrient recycling, outer membrane vesicle-mediated host immune modulation, maintenance of intestinal barrier integrity, microbiota homeostasis, colonization resistance, and its potential as a next-generation probiotic. We further discuss two emerging translational areas: its production of neuroactive metabolites involved in gut–brain communication and its role in shaping responses to cancer immunotherapy through the toll-like receptor 4/interleukin-12/T helper 1 axis in combination with immune checkpoint blockade primarily shown in murine models and observational human studies. Finally, we highlight current limitations, including reliance on animal models, lack of clinical validation, incomplete metabolite characterization, and a lack of understanding of microbiome–immune interactions, and provide a blueprint for future directions in multi-omics, microbial engineering with clustered regularly interspaced short palindromic repeats, and synthetic biology for precision microbiome medicine.

Received: 10 May 2026 | Revised: 8 July 2026 | Accepted: 10 August 2026 

Conflicts of Interest

Indra Mani is the Editorial Board Member for Medinformatics and was not involved in the editorial review or the decision to publish this article. The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Author Contribution Statement

Dishi: Conceptualization, Methodology, Writing – original draft, Writing – review & editing. Indra Mani: Conceptualization, Writing – original draft, Writing – review & editing, Supervision, Project administration.