The location of genes controlling radiation sensitivity in Escherichia coli

By conjugation between Hfr and F − strains, the location on the bacterial chromosome of various genes controlling sensitivity to ultraviolet irradiation was determined in Escherichia coli strain B, strain K12S and strain CR 34. On account of their colony-forming ability after ultraviolet irradiation, the radiation sensitive mutants bearing the various markers studied appeared to fall into two classes: (a) extremely radiation-sensitive mutants hcr − , dar 1 − , dar 5 − and dar 6 − ; and (b) strains B s −2 , dar 3 − , dar 3 − and dar 4 − with a radiation sensitivity intermediate between that of the extremely sensitive strains and that of their corresponding wild types. Strains B s −2 , dar 2 − and dar 4 − were able to propagate certain ultraviolet-irradiated bacteriophages, whereas the other mutants hcr − , dar 1 − , dar 3 − , dar 5 − and dar 6 − were unable to do so. According to the results of the conjugation experiments each mutant appears to belong to one of three distinct linkage groups. The markers B s −2 , dar 3 − , dar 2 − and hcr − are located in a region between the markers thr and ile ; the markers dar 1 − and dar 6 − are closely linked to gal ; the markers dar 4 − and dar 5 − are closely linked to his . In addition the gene phr , that controls the recovery from lethal UV damage by subsequent illumination with visible light (photoreactivation), was found to be closely linked to gal .