FLOW-CYTOMETRY DEMONSTRATES BACTERIOCIN-INDUCED INJURY TO LISTERIA-MONOCYTOGENES

Flow cytometry was used to study the effect of the bacteriocin leucoci n B-TA11a on Lister-in (L.) monocytogenes. Mixed proportions of dead a nd live control populations were analyzed by flow cytometry to determi ne detection limits of the Dead/Live Baclight Bacterial Viability Kit( TM). High correlations for how cytometric detection of defined proport ions of live or dead cells in mixtures between 10 and 100% of dead (r( 2) = 0.97) or live (r(2) = 0.99) cells were obtained. However, mixture s containing less than 10% of either Live or dead control cells gave c orrelations below 0.72. The growth of L. monocytogenes in the absence and presence of leucocin B-TA11a was analyzed by flow cytometry with B aclight, plate counts, and optical density measurements. Although leuc ocin B-TA11a initially inhibited listerial growth, the uptake of both Baclight dyes suggested that cells remained viable but became leaky, p ossibly indicating bacteriocin-induced pore formation in the target me mbranes.