FIGURE 2.

Salmonella Typhimurium IgaA variants in conserved cysteines show distinct capacities to repress the RcsCDB system. (A) IgaA was detected in western assays using samples obtained from bacteria grown in LB medium at 37°C to mid-exponential (OD₆₀₀ = 0.2) or stationary (OD₆₀₀ = 2.0) phase. Note the degradation of the IgaA cysteine variants when bacteria reach the stationary phase. The previously characterized IgaA variant R188H (Dominguez-Bernal et al., 2004) was used as control of protein unstable in stationary phase. Numbers on the left indicate the position of molecular weight markers (in kDa). (B) Activity of the RcsCDB system monitored with a gmm::lacZ reporter fusion in bacteria growing to exponential or stationary phases. gmm encodes an enzyme involved in synthesis of the colanic acid capsule and is positively regulated by the RcsCDB system. Data are the average and standard deviation of three independent experiments. The averages are shown as numbers on top of the respective bars.