As shown in Fig. 1, single staining negatively affected culturability of L. lactis subsp. lactis S1 on solid media compared with the identically handled control. Fluorescent labelling of L. lactis subsp. lactis S1 with 5 or 50 mM cFDA significantly (P < 0.05) decreased plate counts to the same extent (averaged 15.4%; for cFDA-SE averaged 10.9%). While a decrease by 10.0 and 83.7% was detected after single staining with 1.6 or 40 mM PI, complete growth inhibition on solid media was recorded after exposure of L. lactissubsp. lactis S1 to 2 mM TOTO-1.