Scientists have discovered 37 life forms in the warm, moist caverns deep beneath the rugged terrain of our teeth. Using DNA analysis, a Stanford University Medical Center team has found surprising new bugs in the mouths of healthy volunteers. The mouth is awash with bacteria -- nearly 500 strains have been identified -- most of them helpful little critters that digest food and fend off more menacing intruders. BUT the newcomers, reported in today's Proceedings of the National Academy of Sciences, were discovered through a form of  DNA TESTING  that scientists say may uncover countless more surprise microbes. Understanding exactly what lives in our mouths may help in battles ranging from gingivitis to HEART DISEASE. Says Stanford's David Relman, lead author of the study, in a scientific mouthful: ''Sequence-based environmental microbial surveys have taught us that cultivation methods woefully underrepresent the true extent of bacterial diversity.''

    Also see: BACTERIAL CULTURES