Microbes are ubiquitous in nature. They can be found on our skin, on our cell phones, in our water bottles, and pretty much anywhere else you can think of. In the human gut, there is a complex microbial ecosystem that consists of approximately 1 kg of bacteria in an average adult (similar to the weight of the human brain). The number of genes within the human gut microbiome are thought to outnumber the genes in the human body.
Scientists believe that the microbes in our gut can affect the way we feel and act. For example, impacts on cognitive function and fundamental behavior patterns, such as social interaction and stress management can occur.
It is also believed that what we eat can affect the growth of different types of microbes which can, in turn, affect the types of foods we eat. The more unhealthy we eat, the more the "unhealthy" bacterial populations in our gut continue to thrive. These "unhealthy" microbes have been linked to diseases such as obesity and diabetes. We can reverse the growth of these populations by making better food choices to support the growth of "healthy" microbial populations.
The use of fecal transplants is also being investigated to help battle these diseases - that is - transplanting fecal matter from patients with healthy microbiota to help "jump start" microbial populations in patients with unhealthy microbiota.