Cell length and cell wall thickness of <i>L. monocytogenes</i> strains.

aMean cell lengths were determined by measuring 100 cells of each strain grown in the presence (+ PenG) or absence of 0.09 µg/ml penicillin G. The analysis was performed using two independently prepared samples. From each independent sample, equal numbers of cells were analyzed ± standard deviation (SD). bMean cell wall thickness was determined by measurement of 20 cells of each strain grown in the presence (+ PenG) or absence of 0.09 µg/ml penicillin G. The analysis was performed using two independently prepared samples. From each independent sample, equal numbers of cells were analyzed ± standard deviation (SD). cSignificant differences following growth in the presence and absence of penicillin G (Student's t-test; P<0.05). dSignificant differences between the studied strains (Student's t-test; P<0.05).