FIG 3.

TcyABC and TcyP are required for sensitivity to selenocystine and utilization of cystine as a nutrient sulfur source. (A) WT and tcyA::Tn strains were plated as a lawn on TSA, and a disk supplemented with 100 mM selenocystine was added to the plate. The mean zone of inhibition of at least three independent trials is presented. The dotted line represents the disk diameter (6 mm). (B) WT, tcyA::Tn, tcyP::Tn, and tcyA tcyP (tcyAP::Tn) double mutant strains were cultured in PN medium supplemented with 25 μM cystine as the sole sulfur source. (C) WT, tcyA::Tn, tcyP::Tn, and tcyAP::Tn strains were cultured in TSB. Measurements represent at least three independent trials. Error bars represent ± 1 standard error of the mean. * indicates P < 0.05 determined from Student's t test.