FIG 3.
Phenyl-lactic acid (PLA) is a robust killing agent in the CFS of L. crispatus. (A) H-NMR spectroscopy comparing the profiles of LC9873-HH1B subfraction, PLA-L, and PLA-D. The peaks at δH 3.34 represent trace amounts of MeOH in the HH1B subfraction. The peak at δH 4.89 corresponds to water. (B) A chemical standard identical to LC9873-HH1B subfraction (and its methylated analogue MR) were solubilized in a 10% DMSO-90% MRS mixture and tested for killing activity against E. coli K-12. The dotted line represents the limit of detection (1,000 CFU/ml) for the bactericidal activity assay.