FIG 6.

(A) Growth curves of the DL100 (Wt) and pilAY32F strains in insoluble Fe(III) oxide medium. Cells were provided with 100 mM poorly crystalline Fe(III) oxides and 15 mM acetate. Ferrozine assays were applied to determine the concentration of Fe(II) produced by bacterial reduction of Fe(III). The results are averages from eight biological replicates from two independent experiments. The error bars are standard errors of the means. (B to G) Confocal microscopic analysis of the isogenic wild-type DL100, pilAY32F, and ΔpilA biofilms formed on insoluble Fe(III) oxide-coated glass. Images were taken after incubation for 24 h in medium with 40 mM fumarate, and 4 days later, after the fumarate was removed. Bars, 70 μm. (H) Average cell growth of the wild-type DL100, pilAY32F, and ΔpilA strains in biofilms attached to insoluble Fe(III) oxide-coated glass. Cell densities were measured after incubation for 24 h in the presence of 40 mM fumarate and 4 days later after fumarate was removed. The results are the averages from six biological replicates from two independent experiments. The error bars are standard errors of the means. Statistical analysis was performed by Student's t test; *, P < 0.008; ns, not significant.