Genetic control of prophage induction in haemophilus influenzae after exposure to psoralen plus near-UV light.

Prophage S2 could be induced by psoralen plus near-UV light (PNUV) from a wild-type strain of Haemophilus influenzae, from UV light-sensitive strains uvr-1 and uvr-2 and PNUV-sensitive strains PSO1 amd PSO7, but not from a recombination-deficient strain, rec-1. The levels of prophage induction were comparable in the wild type and an ATP-dependent DNase-deficient strain, KW31, even though the PNUV-induced degradation in the latter strain was considerably lower. Prophage induction could be observed even with chloramphenicol present before, during, and 30 min after PNUV treatment.