FIG 6 .
An NvarAL suppressor mutant cannot be complemented by supplying wild-type csrA on a plasmid. Expression of wild-type CsrA in the absence of functional VarA is toxic to the cells, and leads to production of OmpU in the absence of NRES. (A) Strains N16961 (WT), NvarAL-3 (ΔvarA::cam csrA.T11P), NvarAL-3/pWKS30, and NvarAL-3/pWCsrA were grown overnight in LB broth and then subcultured 1:100 into fresh LB broth and grown to the stationary phase. (B) Strains N16961 (wild type [WT]), NvarAL-3/pWKS30, and NvarAL-3/pWCsrA were grown overnight in LB broth and then subcultured 1:100 into T medium with or without 12.5 mM NRES mix. Cells were harvested in the mid-log phase, and whole-cell preparations were resolved by SDS-PAGE (10%) and stained by Coomassie blue.