DETECTION OF XERC AND XERD RECOMBINASES IN GRAM-NEGATIVE BACTERIA OF THE FAMILY ENTEROBACTERIACEAE

XerC and XerD are site-specific recombinases of the lambda integrase f amily,which resolve multimeric replicons to monomers by acting at spec ific sites such as cer, ckr, nmr, parB, and psi, which are found in pl asmids, or at the dif site found in the Escherichia coli chromosome. B y using Southern hybridizations to cloned E. coli xerC and xerD genes and a cer-nmr plasmid-based resolution assay, the presence of these ge nes in several species of Enterobacteriaceae is shown.