The human microbiome has emerged as a central regulatory hub governing physiology across interconnected organ systems, exerting profound influence over metabolism, immune homeostasis and neuroendocrine signalling. Microbial consortia inhabiting the gastrointestinal tract, oral cavity, cutaneous surface, respiratory epithelia, urinary tract and reproductive mucosae establish dynamic symbiotic networks essential for maintaining physiological equilibrium. Disruption of this microbial balance, termed dysbiosis, constitutes a mechanistic driver rather than merely a consequence of chronic and recurring pathological states. In the gut, depletion of short-chain fatty acid (SCFA)-producing bacterial taxa precipitates epithelial barrier compromise, metabolic endotoxaemia and perturbations in glucose and lipid homeostasis. Dysbiotic transitions in the respiratory, cutaneous, and urogenital compartments trigger sustained immune hyperactivation, opportunistic pathogen expansion, and self-perpetuating inflammatory cascades. These mechanistic insights have catalysed the emergence of microbiome-targeted therapeutics designed to reprogram microbial ecosystems rather than suppressing downstream disease manifestations. Probiotics, prebiotics, synbiotics, postbiotics and faecal microbiota transplantation modulate host physiology through competitive pathogen exclusion, epithelial reinforcement, metabolic signalling and immunoregulation. Contemporary advances in multi-omics profiling, synthetic biology and personalized microbiome analysis now enable the rational design of engineered microbial strains and tailored microbial consortia operating with cellular and tissue-level specificity. Despite significant technological progress, substantial challenges persist, including inter-individual microbiome variability, long-term colonization stability and regulatory frameworks, yet microbiome engineering holds transformative potential to reshape clinical practice by targeting the ecological architecture underlying human biology, thereby restoring multisystem homeostasis and circumventing disease development at its mechanistic foundation.

Keywords: human microbiome; dysbiosis; microbiome engineering; therapeutic interventions; host–microbe interactions; precision medicine