The gut microbiome is critical to maintaining health, as its interactions influence nutrient absorption, resistance to infection, and immune system function.[1] An imbalance in microbial interactions, called dysbiosis, is associated with diseases such as obesity, type 2 diabetes, inflammatory bowel disease, colon cancer, rheumatoid arthritis, and multiple sclerosis.[1][4] A reduced microbial diversity and an altered ratio of the phylum Firmicutes to Bacteroidetes are observed in obese individuals.[1] In inflammatory bowel diseases, the number of beneficial bacteria such as Faecalibacterium prausnitzii decreases and pathogenic Escherichia coli increases, which contributes to chronic inflammation.[1] The study introduces a new gut health index that measures microbial interactions as a marker of health and disease.[2][3] These interactions involve cross-feeding between microbes for metabolic efficiency and regulation of the host epithelial barrier.[1] The microbiome also influences the efficacy of cancer immunotherapy through modulation of immune checkpoints.[1]