Bacteria feed on stinky breath.

Bad breath is something that most people fight hard to avoid. Now, scientists have isolated from people's mouths bacteria that aid in that battle. The microbes consume the chemicals that cause mouth odor.

Last year, Ann P. Wood of King's College London and her colleagues reported that a group of bacteria, known as methylotrophs, live off chemicals that emanate from smelly feet. These bacteria eat methylated sulfur compounds, chemicals that result from the breakdown of amino acids.

Further investigations by others showed that these compounds are also present in people's mouths--causing some types of bad breath. Wood's team wondered whether methylotrophs were there as well. No previous study had shown that methylotrophs normally live in the mouth.

Wood and her colleagues swabbed the mouths of 16 volunteers, including people with good oral health and others with various stages of periodontal disease. The scientists then wiped the swabs on lab dishes with nutrients that would support the growth of only methylotrophs. They also used molecular tools to search the swabs for genes present only in these bacteria.

The team reports in the August Environmental Microbiology that several types of methylotroph species gobble up bad breath compounds in the mouths of all the volunteers, regardless of their oral health. Wood hypothesizes that in some people, the proportion of methylotrophs among mouth bacteria may be low, leading to chronically high amounts of the stinky sulfur compounds.