Microbes dominate as the most abundant life form on Earth, occupying almost every terrestrial, aquatic and biological ecosystem on our planet. Humans are no exception. Throughout our lives, we provide residence to symbiotic bacteria, known as the microbiome, on virtually all environmentally exposed surfaces. The vast majority of these microbes are harbored in the gastrointestinal tract where bacteria can outnumber human cells by 10-fold (thus, we are all 90% bacteria on a cellular level!). Many vital host functions are provided by the microbiome, including the synthesis of vitamins, digestion of complex polysaccharides and resistance to infectious agents. Millions of years of co-evolution have inextricably linked the health of mammals to their microbiomes. Therefore, uncovering the evolutionary basis of host-bacterial mutualism represents untapped possibilities to advance our understanding of fundamental aspects of human biology.

Over the past several years, our laboratory has been interested in the connections between gut bacteria and the immune system. Particularly, our work has discovered how the microbiome promotes beneficial immune responses that prevent and treat disorders such as inflammatory bowel disease (IBD) and multiple sclerosis (MS) in animal models. More recently, we have become interested in applying concepts learned from our research of the immune system to link gut bacteria to the nervous system. Along these lines, we have exciting new evidence that the microbiome affects autism in mice, and that specific probiotics provide benefits for behavioral and non-behavioral symptoms of this enigmatic disease. The Watson lecture will explore the fascinating connections between gut bacteria and the two organ systems that are ‘educated’ by environmental cues throughout life, the immune and nervous systems, and describe revolutionary approaches to uncover potentially novel therapies for complex human diseases.

Presented by: Caltech Committee on Institute Programs