FIG. 5.

rrnB P2 is stringently controlled but does not require ppGpp for growth rate-dependent regulation. (A) RNA transcribed from rrnB P2 promoter-lacZ fusions was measured directly by primer extension following amino acid starvation induced by serine hydroxamate addition to a culture growing exponentially in LB medium (A₆₀₀ of ∼0.3). The identity of the rrnB P2 promoter and the strain background are indicated for each sample. Symbols: •, RLG5014, wild-type (WT) rrnB P2(−112 to +7); ▪, RLG3987, mutant rrnB P2(−112 to +7; C−5A,A−4T,C−3A); ▾, RLG6982, wild-type rrnB P2(−112 to +7) in a relA strain. The average and standard deviation of three independent experiments are shown. (B) β-Galactosidase activity from an rrnB P2 core promoter-lacZ fusion, P2(−37 to +7), as a function of growth rate in wild-type and relA spoT mutant strains. Symbols: ▾, RLG3851, wild-type strain; •, RLG3866, relA spoT mutant strain. Data from two independent experiments are shown for each strain.