The Pasteurian Revolution of the 1800’s heralded in a new paradigm of disease. Previously unexplained health phenomena could now be shown to be derived from “germs” – microorganisms invisible to the naked eye. The term “germ” quickly took on a negative connotation and until recently the microbial world has been seen primarily as a breeding ground for invisible enemies to human health. Its pretty incredible actually, the distaste the word “bacteria” instills in us, when really, it simply refers to a domain of prokaryotes. So, is the entire microbial world bent on our demise? I think the answer to this question can be summed up in one simple statistic:
Inside of you there are 1013 human cells and 1014 bacteria cells.
In other words, for every one cell of you there are ten that are not you…Wait, what? The first question this recent discovery may fuel is a stumbled WHAT? But lets digress for a moment and ask, why?
The gastrointestinal (GI) tract in humans provides a home for many (1014) bacterial organisms. The colonization of the GI by bacteria, or microbiota, starts at birth and continues throughout early development and life. These microbiota affect many bodily functions, aiding metabolism, modulating inflammation, and defending against harmful micro-organisms. Each person has a unique profile of microbiota, which is influenced by genetics and the environment. Healthy people, however, generally have similar numbers and distributions of microbiota. Interestingly, disorders of the GI tract have a high comorbidity with mental illness.
It is not surprising then that research in this field has grown, with labs hoping to gain a better understanding of the ‘gut-brain-axis.’ If these labs can elucidate the effect of microbes in the GI tract on the central nervous system, they could shed light on why more than half of patients with irritable bowel syndrome meet the criteria for mood disorders, or how GI tract disorders and mental illnesses can be more effectively treated.
Many researchers are currently focusing on how variations in the composition of microbiota impact physiology and contribute to disease, such as obesity and inflammation. Increasingly, studies have been revealing that these microbiota communicate with the brain and influence its function and behavior, potentially by neural, endocrine, and immune pathways.