Fig. 4.

Biofilm formation and EPS production by T. thermophilus HB27 strains. A, biofilm formation by strains of T. thermophilus HB27 overexpressing various PilF proteins. Biofilms formed on 96-well microtiter plates after 24 h were stained with crystal violet. Surface-attached cells were quantified by solubilizing the dye in ethanol and determining the absorbance at 600 nm. Data are the means of three independent experiments, with each sample tested in triplicate. The asterisks (*) indicate statistical significance (p < 0.05). B, the total EPS content extracted from T. thermophilus HB27 strains expressing wild-type or mutant PilF proteins normalized to each of their bacterial concentrations, as determined in a phenol–sulfuric acid assay. Error bar represents the standard deviations of three independent measurements. Asterisks indicate statistical significance (p < 0.05).