Gut microbiota imbalance and colorectal cancer

The gut microbiota acts as a real organ.The symbiotic interactions between resident micro-organisms and the digestive tract highly contribute to maintain the gut homeostasis.However, alterations to the microbiome caused by environmental changes (e.g. , infection, diet and/or lifestyle) can disturb this symbiotic relationship and promote disease, such as inflammatory bowel diseases and cancer.Colorectal cancer is a complex association of tumoral cells, non-neoplastic cells and a large amount of micro-organisms, and the involvement of the microbiota in colorectal carcinogenesis is becoming increasingly clear.Indeed, many changes in the bacterial composition of the gut microbiota have been reported in colorectal cancer, suggesting a major role of dysbiosis in colorectal carcinogenesis.Some bacterial species have been identified and suspected to play a role in colorectal carcinogenesis, such as Streptococcus bovis , Helicobacter pylori , Bacteroides