On average 4.7 and 10.9% longer lag phases reflected changes in growth behaviour of L. lactis subsp. lactis S1 in liquid media due to fluorescent labelling with cFDA or cFDA-SE (average of percentage deviation for 5 or 50 mM; Table 1). Besides significant (P < 0.05) lag phase elongation after single staining with 40 mM PI (28.7%) or 0.2 mM TOTO-1 (23.7%), no growth was detected for L. lactis subsp. lactis S1 cells labelled with 2 mM TOTO-1