FIG. 4.

RpoS protects rapidly growing exponential-phase cells against NEM. Exponential-phase cells were grown in M9 medium, and cell viability was determined exactly as described in Materials and Methods. (a) NEM was added at 0.3 mM to cells of Frag1 (RpoS⁺; •). MJF405 (Frag1, clpP::Tn9; ▪), and MJF372 (Frag1, rpoS::Tn10; ▴) at time zero. (b) Cells were grown to exponential phase in M9 supplemented with 0.4% (wt/vol) CAS and then treated with 0.3 mM NEM at time zero (symbols same as panel a except open). The arrows represent no viable cells by the next time point; error bars represent the standard deviation from the mean for one experiment.