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INTRODUCTION
The gut microbiome has become one of the most intensively studied frontiers in biomedical science. Over the past decade, microbiome research has generated remarkable evidence linking alterations in microbial communities with a broad range of communicable and non-communicable diseases. However, as the field progresses toward clinical translation, an important question remains: Are we measuring the microbiome or merely describing it?
A major limitation of current microbiome research is the frequent interpretation of disease-associated alterations based primarily on microbial composition. Increased or decreased abundance of a bacterial genus or species does not necessarily reflect its functional activity. Closely related strains can possess substantially different metabolic capacities, immunomodulatory properties, colonization characteristics and interactions with the host. Therefore, the future of microbiome science should increasingly shift from asking “who is there?” toward understanding “what are they doing, under which conditions and how does the host respond?”
The next generation of microbiome research must consequently progress beyond taxonomic cataloguing toward functional and mechanistic understanding. Species-level classification can obscure profound strain-level differences in metabolic pathways, immune interactions, colonization capacity and therapeutic potential. The same bacterial species may contain strains with markedly different or even opposing, effects on host physiology. Consequently, attributing a uniform beneficial or harmful effect to an entire species may overlook substantial strain-level heterogeneity, potentially leading to oversimplified biological interpretations and limiting the accuracy of microbiome-based clinical translation.
Microbiome-derived metabolites, including short-chain fatty acids (SCFAs), secondary bile acids, indole derivatives, polyamines, gamma-aminobutyric acid (GABA), ethanol and other bioactive molecules, can influence epithelial integrity, immune-cell differentiation, metabolic signaling and communication with distant organs. Elucidating these pathways requires two or more omics layers, together with immune phenotyping and relevant host characteristics, rather than treating each biological layer independently.
Nutrition represents another critical dimension that warrants far greater attention. Diet is not merely a confounding variable in microbiome studies; it is one of the principal determinants of microbial ecology and metabolic output. Dietary fibres, resistant starch, polyphenols, fermented/functional foods and culturally specific dietary patterns may involve substantially different microbial responses among individuals.
Future clinical microbiome research should prioritize longitudinal and intervention-based study designs rather than relying predominantly on cross-sectional associations, thereby enabling stronger inference of temporal relationships and biological causality. Integrating microbial ecology with nutrition, immunology, host genetics and metabolomics offers a systems-level framework for deciphering complex host-microbe interactions and identifying microbial functions and molecular signatures with predictive and therapeutic relevance. Such advances could provide the foundation for developing precision microbiome- and nutrition-based interventions tailored to individual microbial and host phenotypes, ultimately accelerating the translation of microbiome discoveries into clinically relevant approaches for disease prevention and management.