I have bad breath. What's living in my mouth?

If you suffer from halitosis, you're probably aware that the smell emanating from your mouth is connected to the foods you eat, the beverages you drink and the number of times you brush your teeth each day. While all of these factors are major determinants of whether your breath smells sweet or sour, they all depend on a more basic agent of odor - namely, microbes.

Your tongue, teeth and palate are a surprisingly diverse place, bacteriologically speaking. Not only are their millions upon millions of individual little life forms living in your mouth, but there are hundreds of different species, each with its own function.

How many bacteria are in your mouth at any one time? It's tough to say, but most researchers estimate that the figure extends to at least 10 digits. An article in Resident Dental Hygienist Magazine estimated that the average mouth contains 20 billion microorganisms.

However, that figure may vary. If you use a specialty breath freshening rinse or toothpaste, the number of bacteria living in there may be lower. On the other hand, using an oral care probiotics product won't reduce the number of microbes but can at least replace odor-causing bacteria with less irritating varieties.

If you neglect to clean your teeth, your bacteria count could go through the roof. According to data published by the Chicago Tribune, an unclean mouth could have as many as 1 billion microorganisms on each tooth. Assuming those teeth haven't decayed and fallen out - and adding the bacteria living on the tongue, gums and palate - a person with poor dental health and raging bad breath could be leasing their mouth to 100 billion tenants.

As for the diversity of these bacteria, numerous studies have shown that between 500 and 600 species live in the oral environment at any one time.

One study, published in the Journal of the American Dental Association, found a minimum of 38 varieties in participants' mouths. All volunteers with halitosis tested positive for the species Solobacterium moorei.

Another report, appearing in the Journal of Clinical Microbiology, stated that people with bad breath tended to have Atopobium parvulum and Eubacterium sulci, as well as S. moorei, in their mouths.

These bacteria thrive in dryness. Regardless of which species populate your oral zoo, maintaining a moist, clean mouth and using probiotics can keep oral odor to a minimum.