Dysbiosis refers to the imbalance of microbial flora inside the body, for example an imbalance within the gut-microbiome. This imbalance may be caused by one species of gastro-intestinal bacteria taking over and growing at a rapid rate. This species would require more nutrients than usual as it is growing more, and this causes there to be less nutrients available for other bacterial species which affects their growth and survival. Dysbiosis might also lead to a less diverse gut-microbiome.
Maintaining a healthy balance within our gut-microbiome is extremely important as dysbiosis has been linked to many digestive conditions including Irritable bowel syndrome, inflammatory bowel disease, coeliac disease and some forms of colorectal cancers. It is thought that dysbiosis may also play a role in psychological disorders too, through the gut-brain axis.