Is 600 a Crowd? Ask Your Saliva.

In addition to helping us fight tooth decay, saliva is also home to over 600 types of bacteria. Scientists (again with the scientists) have found that the variety of bacteria in the saliva is not as related to diet and environment as they had suspected.  Because of all the colonies of bacteria, saliva actually contains more DNA than blood does.

The article mentions one of the benefits of saliva. Humans are not as good as animals at detecting toxins, so we vomit more than other species. Saliva helps to guard against the damage of the acid when we throw up (Charming, I know.).

Most bacteria don't help us at all. They are just along for the ride. So keep your mouth clean and visit your dentist regularly before a new species gets named after you.