The human microbiome, comprising trillions of microorganisms across multiple body sites, is increasingly recognized as a key contributor to host immunity, metabolism, and neurobiology, influencing development and disease susceptibility throughout life. Rather than acting in isolation, microbial communities operate within a complex host-environment system shaped by genetics, diet, lifestyle, and medical exposures. Conceptually, the microbiome can be understood as part of a host-microbe meta-organism and, from a translational perspective, as a dynamic and potentially modifiable organ system. While short-term perturbations such as antibiotics may transiently disrupt microbial ecosystems, persistent maladaptive configurations, commonly termed dysbiosis, are associated with metabolic disease, chronic inflammation, neurodevelopmental disorders, and cancer, although causality remains context dependent. This review synthesizes the functional roles of beneficial microbes and their metabolites, the mechanistic and clinical implications of dysbiosis, and immune pathways shaped by microbial signals. We further discuss emerging therapeutic strategies, including dietary modulation, probiotics, engineered microbial consortia, postbiotics, and fecal microbiota transplantation, enabled by multi-omics technologies, organoid models, and computational frameworks. Key challenges include defining context-specific microbial health, ensuring durable engraftment, and addressing regulatory and ethical considerations. Framing the microbiome as a dynamic component of host physiology provides a foundation for microbiome-guided precision and preventive medicine.
Bautista et al. (2026) studied this question.