Ordered intracellular RecA-DNA assemblies: A potential site of in vivo RecA-mediated activities

The inducible SOS response increases the ability of bacteria to cope with D NA damage through various DNA repair processes in which the RecA protein pl ays a central role. Here we present the first study of the morphological as pects that accompany the SOS response in Escherichia coil. We find that ind uction of the SOS system in wild-type bacteria results in a fast and massiv e intracellular coaggregation of RecA and DNA into a lateral macroscopic as sembly. The coaggregates comprise substantial portions of both the cellular RecA and the DNA complement. The structural features of the coaggregates a nd their relation to in vitro RecA-DNA networks, as well as morphological s tudies of strains carrying RecA mutants, are all consistent with the possib ility that the intracellular assemblies represent a functional entity in wh ich RecA-mediated DNA repair and protection activities occur.