FIG 5.

Oxygen level affects colony formation. To assess the effect of oxygenation on the growth of strains, overnight cultures were diluted and plated for isolated colonies on LB agar with supplements as indicated, and colony diameters were measured after 24 h at 37°C under the indicated oxygen condition. (A) Comparison of growth in aerobic and microaerobic environments for the wild-type, null, and single-system strains. (B) Comparison of growth in aerobic and anaerobic environments for the wild-type and null strains. (C) Comparison of null strain growth in aerobic and anaerobic environments with the iron chelator EDDA (20 μg/ml) as indicated. The data are means and standard deviations and are representative of biological replicates. * indicates significance as determined by two-way analysis of variance, Šidák multiple-comparison test, P value of <0.0001. ** indicates significance as determined by one-way analysis of variance, Holm-Šidák multiple-comparison test, P value of <0.0001. LBA, LB agar.