Northern blot showing the effect of zinc on the transcription of zrfA and zrfB. Strain AF14 was grown in SD medium supplemented as follows: SD medium plus Zn2+ plus Fe3+ plus Cu2+ (1), SD medium minus Zn2+ plus Fe3+ plus Cu2+ (2), SD medium plus Zn2+ minus Fe3+plus Cu2+ (3), SD medium plus Zn2+ plus Fe3+ minus Cu2+ (4), SD medium minus Zn2+ plus Fe3+ plus Cu2+ (5), SD medium minus Zn2+ plus Fe3+ plus Cu2+ (6), SD medium minus Zn2+ plus Fe3+ plus Cu2+ plus Mn2+ (7), SD medium minus Zn2+ plus Fe3+ plus Cu2+ plus Fe2+ (8), SD medium minus Zn2+ plus Fe3+ plus Cu2+ plus Cd2+ (9), SD medium minus Zn2+ plus Fe3+ plus Cu2+ plus Co2+ (10), and SD medium minus Zn2+ plus Fe3+ plus Cu2+ plus Ni2+ (11) (metals in boldface type were added at a final concentration of 250 μM). Probes are indicated to the left of each blot.