Is there anything they can’t do?

In the current issue of Maclean’s, I wrote about a global effort to track all the bacteria that live in the human body—a monumental undertaking, since they outnumber our own cells by ten-to-one. It may gross people out to think we’re literally crawling with bugs, but a growing body of research suggests they’re crucial to our health: by now, microbes have been implicated in everything from periodontitis, to obesity, to premature labour.

Today, a new study caught my eye: it looks like bacteria even affect the taste of the food we eat. In the human mouth—where each tooth seems to have its own unique bacterial colony—microbes create food odours from odourless components, allowing us to fully taste fruits and veggies, a Swiss team is reporting.

Some fruits and vegetables release their characteristic odours only after being swallowed, researchers report in the Journal of Agricultural and Food Chemistry (to be published Nov. 12). The team performed sensory tests on 30 trained panelists using grapes, onions and bell peppers, and found that the food’s odourless compounds are processed by bacteria in the mouth, which creates this so-called "retroaromatic" effect. "The mouth acts as a reactor, adding another dimension to odor perceptions," they said.

Queen’s University’s Dr. Elaine Petrof recently toldMaclean’s, "Everyone talks about going to the Amazon rainforest to look for new species. But we’ve got all this stuff inside our own bodies that we don’t know anything about.” As our research into the human microbiome continues, there’s no telling what we could find.