Taking Microbial Medicine
In an abandoned bubble cage in the room housing Gordon’s sterile mice sits a carton of yogurt. Yogurt is full of living bacteria that are meant to be good for you, and Gordon is testing “probiotic” theories about the beneficial use of microörganisms. Technicians feed yogurt to both sterile mice and those that have been purposely infected with one or a few species of bacteria, whose effects on their health and microbial profiles the researchers are trying to gauge.
“Maybe microbes themselves, or microbe-derived chemicals, could become part of our 21st-century medicine cabinet,” suggests Gordon. He envisions a day when a routine doctor’s visit would include an analysis of our microbial inhabitants. “When we eat, should we consider caloric and nutritional value of food as absolute, or should we consider it based on an individual’s microbial community?” he asks. Microbial profiles could also be used in diagnosing, and perhaps even treating, specific diseases.
Metagenomic studies could shed light on public-health issues, too. Microbiologists hypothesize that changes in the way we live–cleaner drinking water and growing use of antibiotics, for example–have changed which microbes colonize our bodies. This in turn may explain, at least in part, why many developed countries are seeing an abrupt rise in certain diseases, such as asthma, which is characterized by an excessive immune response in the lungs. In the absence of some types of bacteria, the immune system may develop or function abnormally. Martin Blaser, a microbiologist at New York University, says that almost everyone used to be infected with the gut microbe H. pylori, which has been linked to ulcers. Now only 10 percent of children in the United States carry the bacterium. Preliminary studies conducted by Blaser link its absence to asthma.
While scientists have been able to connect some disorders, such as ulcers, to the presence or absence of individual bacterial species, they have been unable to identify a single microbial culprit for many others. It’s possible that changes in many microbial populations must occur together to boost the risk of contracting a particular disease. “Maybe it’s the structure of the community that plays a role,” Gordon says.
Back in the bubble cages, mice are eating, sleeping, and nursing their young. By showing how microbial populations affect their animal hosts, the studies taking place in the mice’s sterile quarters could eventually have profound consequences for human health. But for now, they represent the first tentative, tantalizing forays into a mysterious microscopic world.
Emily Singer is the biotechnology and life sciences editor of Technology Review.