Bacteria love a habitat that is dark, damp, warm, and sheltered, and the human mouth provides such a place. Everyone’s mouth is home to teeming multitudes of oral bacteria, but there are certain measures a person can take to reduce the amounts of harmful germs that can cause oral infections. Here’s a guide to the bacteria that reside around your teeth, gums, and tongue, including how many there may be and how you can control their numbers.