Fig. 4

Dependence of dynamics of A. proteus population on LLO-production by bacteria. Two isogenic pairs, L. monocytogenes strains EGDe (LLO-producing, white) and EGDeΔhly (LLO-lacking, light grey), and L. innocua strains NCTC10288 (LLO-lacking, dark grey) and NCTC10288::pHly/PrfA* (LLO-producing, black t) were used to feed A. proteus directly or via an intermediate consumer T. pyriformis. Cultures were maintained for 24 h. Rates of changes in the number of A. proteus are shown. Positive rates mean an increase in the amoebal population while negative rates mean a decrease. Lm: L. monocytogenes; Li: L. innocua; Tp: T. pyriformis; LLO: listeriolysin O; CFU: colony forming units. The data represent a mean ± SD from three independent experiments with the initial A. proteus population taken as 100%. *p < 0.05, **p < 0.005