Iron availability impacts the growth and survival of bacteria and fungi. (A) Quantification of colony forming units (CFU) for B. subtilis and M. luteus on LB agar medium and S. cerevisiae on YPD agar medium, supplemented with 0, 160, or 320 µM 2,2'-dipyridyl. Plates were incubated for 48 h. All values represent means ± standard errors of results from three or four biological replicates. Asterisks indicate statistically significant differences (*, P values of 0.05 to 0.01; **, P values of 0.01 to 0.005; ***, P values below 0.005; NS, no significant difference) as determined by a Student's t test. Note that M. luteus and S. cerevisiae did not grow at 320 µM 2,2'-dipyridyl. (B) Growth curves of B. subtilis and M. luteus in liquid LB medium and S. cerevisiae in liquid YPD medium, supplemented with 0, 160, or 320 µM 2,2'-dipyridyl and grown for 8 h. Values represent means ± standard errors of results from three biological replicates.