This is Scientific American's 60 Second Science.

I'm Christopher Intagiyata.

Every day, you produce one to two liters of spit.

It kick starts digestion and helps you swallow and it helps prevent bacterial infection in your mouth.

But that still seemed like a lot of energy put into something if it's only going to do that small task.

Esther Bullet, a biophysicist at the Boston University School of Medicine.

And we wondered whether there was something else that it was doing as well, that maybe it had a farther reach

than just preventing infections in the mouth.

So she and her team looked farther down the pipes,

and whether certain proteins and spit

might also disrupt the work of bad bugs in the gut.

They grew cells taken from the small intestine of a 51-year-old

woman and they also grew a batch of pathogenic E. coli bacteria, the kind that caused

traveler's diarrhea. The E. coli have little hair-like extensions on them, called

pealie, that grab on to the intestinal cells. But fewer of the E. coli were

able to successfully attach to the intestinal cells when a particular saliva protein called

his statin five was hanging around. You might think of the E. coli like

pirate ships trying to dock at a port. What the hisatin five does is

stop the pirate ships, the bad bugs, from using their ropes, the pely, to dock.

Because if you can't bind, then you can't start an infection.

So no adhesion, no infection, no disease. The study is in the journal of

infectious diseases. The salivary protein can be chemically synthesized, stored as a powder,

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