FIG. 2.

A low concentration of nickel promotes biofilm formation on stainless steel coupons. Biofilms, formed by the GFP-labeled strain MG1655 ompR234 (PHL1359), were observed under a confocal microscope after 24 h of growth, as described in Materials and Methods. (A) Uniform biofilm grown without nickel. (B) Irregular three-dimensional structured biofilm grown in the presence of 100 μM of nickel. (C) Microcolonies grown in the presence of 300 μM of nickel. (D) Mean biovolumes calculated from three z-stacks made on each coupon. Variance analysis was performed using Statgraphics (Manugistic, Inc., Rockville, MD). The P value reflects the probability that the mean of the biovolumes with exposure to nickel is equal to the mean of the biovolumes without exposure (P < 0.0001).