People tend to get stinky when they work up a sweat. The culprit behind body odor is an army of armpit-dwelling microbes. These tiny microorganisms break down substances produced by sweat glands. In the process, some of the bacteria, like Staphylococcus hominis, create smelly molecules called thioalcohols. Scientists at the University of York in England recently discovered the enzyme they believe these bacteria might use to carry out this chemical reaction.

To make sure this specific enzyme was behind S. hominis’s production of foul-smelling thioalcohols, the scientists ran a test. They inserted genes that carry the instructions to make this enzyme into a nonstinky bacteria called Staphylococcus aureus. It worked! S. aureus started releasing a “cheesy, oniony smell,” says Gavin Thomas, a microbiologist who led the study.