New ultrafast DNA-sequencing technologies allow scientists to study the genetic makeup of entire microbial communities, each of which may contain hundreds or thousands of different species.

For the first time, microbiologists can compare genetic snapshots of all the microbes inhabiting people who differ by age, origin, and health status. By analyzing the functions of those microbes’ genes, they can figure out the main roles the organisms play in our bodies.

Ultimately, researchers hope to find out precisely how microörganisms lower or increase the risk of contracting certain diseases. Armed with that information, physicians might one day use an individual’s microbial profile to diagnose a disease, or manipulate the organisms in our gut to treat or prevent health problems.