Can catalyze the hydrolysis of ATP in the presence of single-stranded DNA, the ATP-dependent uptake of single-stranded DNA by duplex DNA, and the ATP-dependent hybridization of homologous single-stranded DNAs. It interacts with LexA causing its activation and leading to its autocatalytic cleavage. Cells are more sensitive to UV and MMS, and have no detectable recombinase activity. They are still able to generate phase variants, as do wild-type cells, and surprisingly do so at a 10-fold greater rate. Phase variants irreversibly lose the ability to swim, and undergo changes in their sugar assimilation profile. Belongs to the RecA family.