A technique called 'bead beating.' Photo Credit: Courtesy of California Institute of Technology |
The gut microbiome—the population and variety of bacteria within the intestine—is thought to influence a number of behavioral and disease traits in humans. Most obviously, it affects intestinal health. Cancer, inflammatory bowel disease, and celiac disease, for example, are all affected by the gut microbiome. But recent research at Caltech and other research centers has identified connections between the gut microbiome and diseases such as Parkinson's disease and multiple sclerosis as well as links between the gut microbiome and the presence of autistic behaviors, anxious behaviors, and a propensity to binge-eat sweets. (Most of this work has been done in the laboratory of Sarkis Mazmanian, Caltech's Luis B. and Nelly Soux Professor of Microbiology, who works mainly on mouse models.)
Looking directly at the human gut and the bacteria that make this space their home is often performed with sequencing—a process that analyzes the DNA sequences that make up each organism. However, this process is difficult in the intestine largely because the amount of microbial DNA in the gut is miniscule in comparison to the amount of host DNA. In intestinal tissue, roughly 99.99 percent of the DNA present is from the host organism; only 0.01 percent is microbial DNA.
However powerful the effects of these microbes, it is hard to understand their role without knowing their composition. Microbiome studies often rely on studies of feces and saliva, but these are quite different from the ecosystem of the gut itself.