Bacteria make up most of life on Earth. It's life we can't see. Some bacteria thrive in such extreme environments as the boiling water of the hot springs in Yellowstone National Park, or in the driest place on Earth - the Atacama Desert of northern Chile. But, according to Greg Caporaso in the Center of Microbial Genetics and Genomics at NAU, the most extreme environment for life is inside the human body.
Caporaso says, "we've evolved an immune system that is very selective in allowing certain bacteria to live and certain bacteria not to live. From a bacterial perspective," he says, "dealing with the vertebrate immune system is a lot harder than dealing with extreme temperature or extreme aridity."
In studying the human microbiome, Caporaso and others have found that when they compare any 2 or us, we're essentially 99 percent alike. But when comparing the bacterial composition of our intestines, we might be as much as 55 percent different. And those microorganisms may determine whether we have the guts to fight disease.
"One of the classic examples in the field now," Caporaso says, "is the association between the gut microbioda - the microbes that live in the gut - and obesity. So individuals who are obese tend to have more similar communities to one another living in their gut than they do to individuals who are lean."
Caporaso's research suggests that whether we have a disease, or how well we respond to treatment for a disease, may be more related to what's living in us than our own genetic make-up.
"It really holds the promise that we might be able to treat human diseases by altering the microbial communities of our bodies," Caporaso says. "We really do live on a microbial planet."