FIG. 1.

(A) Inhibition of MG1655 ompR234 (PHL818) growth by increasing the concentration of nickel. The OD₆₀₀ was measured either in cultures that had been shaken (open circles) at 130 rpm or in static cultures (dark triangles), as described in Materials and Methods. The incubation period was 24 h, at 30°C, in LB/4 medium in the presence of increasing nickel concentrations ranging from 0 to 400 μM. (B) Enhancing effect of the low concentration of nickel on biofilm formation on polystyrene. Differential growth of MG1655 ompR234 (PHL818) in supernatant (dark diamonds) and biofilm (dark squares) fractions was estimated from the OD₆₀₀ in petri dish cultures, as described in Materials and Methods. The OD₆₀₀ without nickel reached about 1.3 in the supernatant and 0.3 in the biofilm. The addition of supernatant and biofilm fractions resulted in the curve of static growth shown in panel A.