Our Microbiome May Be Looking Out for Itself

You’ve read about parasites that take over an animal and change its behavior for its own purposes. It’s the stuff nightmares are made of. But humans aren’t as immune to these shenanigans as you may think. Carl Zimmer tells us about research into how the trillions of bacteria and other microbes we carry around with us every day may be influencing our behavior -and we’d never know it. Germs in our guts that help us digest food can manufacture chemicals that communicate with each other, and these chemical signals may influence the brain. Studies of mice show that it’s possible.

A number of recent studies have shown that gut bacteria can use these signals to alter the biochemistry of the brain. Compared with ordinary mice, those raised free of germs behave differently in a number of ways. They are more anxious, for example, and have impaired memory.
Adding certain species of bacteria to a normal mouse’s microbiome can reveal other ways in which they can influence behavior. Some bacteria lower stress levels in the mouse. When scientists sever the nerve relaying signals from the gut to the brain, this stress-reducing effect disappears.
Some experiments suggest that bacteria also can influence the way their hosts eat. Germ-free mice develop more receptors for sweet flavors in their intestines, for example. They also prefer to drink sweeter drinks than normal mice do.
Scientists have also found that bacteria can alter levels of hormones that govern appetite in mice.

So far, it sounds pretty benign. After all, microbes who live in us depend on our continued well-being, right? So far, research shows that behavior that benefits microbes doesn’t always benefit the host, but when they harm us, we go full-throttle after them. However, knowing about this mechanism may one day lead to humans being able to control what microbes do in our bodies to our benefit. Read more at the New York Times.