Figure 5. Enhancement of biofilm formation in response to cadmium.

A) Staining of Rhizobium alamii biofilms formed by the wild type strain (wt, upper panel) and the MSΔGT mutant impaired in EPS synthesis (lower panel), using a crystal violet assay (O'Toole et al, 1990). The cadmium concentration increases from left to right (0 to 133 µM; 0 to 15 mg.L⁻¹). B) Biofilms of R. alamii wt (white bars) and MSΔGT mutant (dark bars) were quantified using a crystal violet assay (OD 595 nm) after 72 h of static culture at 30°C. Planktonic growth of R. alamii wt (open squares) and MSΔGT mutant (black circles) was measured in the culture supernatant (OD 600 nm). The error bars represent the confidence intervals (95%) of triplicates.