Fig. 1.

Microbiome dysbiosis in CRC. This figure summarizes factors influencing the gut microbiome, a model for dysbiosis in carcinogenesis process of CRC, and a description of the bacteria species accounting for dysbiosis in CRC. Upper part: factors shaping the gut microbiome: host (genetics and non-genetics), lifestyle (diet, exercise, sleeping time, etc), and environmental (pool of colonizing strains) factors. All those factors may have an influence in the microbiome, which in turn may influence the state of health/disease of individuals. Other factors influencing the state of gut microbiome include stochastic effects, presence of driver/passenger species, its compositional state and metabolomics. Middle part: The multi-step process of carcinogenesis and the influence of the microbiome. As suggested by several authors, imbalances in the normal content of the gut microbiome (gut dysbiosis) lead to colonization of driver bacteria that induce a chronic inflammation of the gut epithelia. This inflammation changes the microenvironment and biofilm and allow a new colonization by passenger bacteria, which may contribute to carcinogenesis process from adenomatosis to tumor formation. Bottom: Bacterial species enriched/depleted in CRC both tumor and feces samples as compared to control samples.