The human body's trillion microbial residents could clue scientists in to new therapeutic drugs.American Chemical SocietyMatt Davenport, a C&EN contributing editor, explains that the human microbiota produces thousands of small molecules. Some have been discovered and tested, but by and large, very little is known about most of them. However, it could be well worth finding out more. Doctors are already prescribing pharmaceuticals based on small molecules made by exotic bacteria from the earth and sea, meaning our own microbes could be an untapped and accessible source of novel drugs. But rifling through all of the microbiota's natural products for a hit is like searching for a needle in a haystack.

To shrink that haystack, one team of scientists took a systematic, computer-assisted approach. They designed software to compare the microbiota's collective genes, or microbiome, against genes that are already known or suspected to play a role in producing small molecules that help keep microbes, and maybe their hosts, healthy. The team found more than 3,000 such gene clusters. One of those, from the vaginal bacteria Lactobacillus gasseri,contains the code for a small molecule that is very similar to a recently discovered antibiotic now undergoing clinical testing. When the scientists tested the Lactobacillus molecule in the lab, they found it attacked gram-positive bacteria, some of which can cause human illness.