Recovery of colony-forming ability and genetic marker activity by UV-damaged Hemophilus Influenzae.

The rate of recovery of UV-irradiated Hemophilus influenzae from acriflavine-sensitized loss of colony-forming ability was studied at various acriflavine concentrations, UV doses, and temperatures. This rate (as calculated from an equation based upon certain assumptions) was on the order of 0.07 per minute per cell at 37 degrees C. This did not vary greatly with UV dose or acriflavine concentration, but did with temperature, giving a DeltaHdouble dagger of about 16 kcal/mole. In another set of experiments, cells bearing two genetic markers (resistance to 2000 mug/ml streptomycin and to 2.5 mug/ml novobiocin) were irradiated and then incubated without acriflavine. DNA extracts made from samples taken after various periods of incubation time were assayed on antibiotic-sensitive cells using acriflavine to inhibit repair during and following transformation. It was found that both in vivo irradiated markers were reactivated in the donor to approximately the same extent (with a rate constant of 0.04 per minute). This result was in contrast to the results obtained when extracted DNA bearing the same markers was irradiated in vitro and used to transform cells. In this latter case the streptomycin marker was much more sensitive than the novobiocin marker. This difference is interpreted as being due to the mechanics of the transformation system.