C. elegans is attracted to diacetyl produced by LAB grown on citrate media. (a) Pre-exposure to the odor diacetyl results in adaptation behavior towards LAB grown on citrate media. Wild-type C. elegans was pre-exposed to 1:5000 dilution diacetyl, 1:5000 dilution benzaldehyde or a control buffer for 80 min, then performed an attraction assay either to diacetyl, LAB grown on citrate media or benzaldehyde. Error bars indicate s.e. Significance was calculated by Student's t-test and P-values are indicated. (b) Attraction was then tested to diacetyl, OP50 on citrate media, or LAB on citrate media with wild-type C. elegans and odr-10(ky32) mutants carrying a mutation in the ODR-10 diacetyl receptor. Error bars indicate s.e. Significance was calculated by Student's t-test and P-values are indicated.