Fig. 4

The biofilm formation by S. salivarius 57.I and its derivatives. a The mass of the static biofilms of S. salivarius 57.I, ΔcodY and CΔcodY. Values are expressed in terms of the means and standard deviations of three independent experiments; quadruplicate samples of each strain were used in each experiment. Significant differences were analyzed by the Student’s t test. **, p < 0.01. b Images of the biofilms in the flow cell system. The biofilms were grown in BMG for 10 h. Live (green fluorescence) and dead (red fluorescence) cells were stained with SYTO9 and PI, respectively, and visualized by CLSM