
Kissing Couples Exchange Mouth Bacteria, Shaping Gut Microbiomes
A Cell Press Blue study finds romantic partners share mouth bacteria far more than gut bacteria, likely due to kissing, and shows mouth bacteria can seed the gut. Analyzing 1,644 saliva–stool samples from 808 people in 207 households, researchers describe a two-step transmission: bacteria spread between cohabitants, then move from mouth to gut, with some gut strains linked to poorer cardiometabolic health, though causality isn’t established; results are correlational and limited by sequencing data.













