Characteristics of a priA knockout mutant with a dnaC suppressor.

aCells were plated on LB plates containing 6 mM MMS. Cells were grown at 30°C.bThe amount of SOS induction was measured using the dinD-lacZ fusion present in each strain. The level of β-galactosidase activity is expressed as Miller units, which are a measure of enzymatic activity per cell density.cThe portion of viable cells forming infective centers when plated on a lawn of GTN932 indicator culture at 42°C was measured.dGTN412 has the following basic genotype, which is shared by GTN430 and GTN522: his::Mucts62 del(priB)302 dinD1::Mud(lac,Ap) del(gpt-lac)5.eThis is a suppressor mutation in dnaC, changing the gug codon for val-135 to aug (met).