FIG. 2.

(A) Northern analysis of the sarU transcript in sarA, agr, sarT, sarR, and sarS mutants and in complemented strains at exponential (OD₆₅₀, ∼0.7) (upper panel) and postexponential (OD₆₅₀, ∼1.7) (lower panel) phases of growth. Expression of the sarU transcript appeared to be higher during the postexponential phase than during the exponential phase in the sarT mutant, a conclusion drawn from multiple repeated experiments. A total 15 μg of cellular RNA was loaded onto each lane. The blot was probed with an 820-bp sarU probe containing the entire open reading frame of the sarU gene. The thin arrow points to the ∼1,200-nt sarU transcript and the thick arrow points to a 1,400-nt transcript (see Discussion). (B) Northern hybridization with the same fragment to the wild-type RN6390, sarT mutant (ALC1905), and to ALC1905 complemented with a wild copy of the sarT gene (ALC2071) and complemented sarU mutant (ALC2381).