Chromosomal rearrangements in Escherichia coli strains carrying the cryptic lambda prophage.

T H E insertion of h into the chromosome of Escherichia coli K12 increases the distance between the loci gal and bio, bracketing the prophage. Thus the frequency of PI mediated joint transduction of gal and bio from a lysogenic donor is considerably lower than that from a non-lysogenic one (ROTHMAN 1965). Accordingly, the frequency of gal-bio cotransduction from a donor carrying a deletion in its prophage should be intermediate between the frequencies found with lysogenic and non-lysogenic strains. prophage the region between genes N and R, including the immunity region, is deleted (FISCHER-FANTUZZI and CALEF 1964; CALEF and FISCHER-FANTUZZI 1965; and MARCHELLI, PICA and SOLLER 1968). Contrary to what should be expected in the case of a mere deletion in the prophage, no P1 mediated gal-bio cotransduction has been observed from the cryptic lysogen U1 60. In addition, no viral genes were transduced with gal and only those situated near bio were transduced with it (ROTHMAN 1965). Thus the deletion in the cryptic prophage present in U160 seems to result from a more complex reorganization of the host chromosome. It was suggested that a chromosome segment was translocated between gal and bio, spacing them enough to preclude joint transduction (FISCHER-FANTUZZI, 1967; and ZAVADA and CALEF 1967). The aim of the present work was: 1) to find whether the absence of P1 mediated joint transduction of gal and bio observed with U160 is a general property of strains carrying a cryptic prophage between these loci, and 2) to detect possible chromosomal rearrangements in cryptic lysogens negative in gal-bio cotransduction. Thus several independent cryptic derivatives were analyzed for gal-bio cotransduction and kinetics of chromosomal transfer. The latter phenomenon was investigated by means of interrupted mating experiments with cryptic Hfr males unable to donate simultaneously gal and bio in PI transduction. In the cryptic