PHOTOREACTIVATION OF ULTRAVIOLET-IRRADIATION DAMAGE IN STAPHYLOCOCCUS AUREUS

Abstract

This study reports the capacity of Staphylococcus aureus strain 7-8 to undergo photoenzymatic repair of UV-irradiation induced damage and compares it to the photoreactivation (PR) response of Escherichia coli strain B. Staphylococcus aureus showed greater inhibition by UV irradiation than E. coli, consistent with its higher adenine and thymine content of DNA. Staphylococcus aureus showed an enhanced rate of photoreactivation with no lag in initiation of the PR response at low PR doses compared to E. coli. Maximum PR capacity of both cultures was about equal and occurred in cultures incubated at 23-25°. The PR responses at 11-12 and 35-37° for S. aureus and E. coli differed although both were capable of PR at each of these temperatures. The PR response of E. coli was directly related to the dosage of PR light (J/m²); however, the photoenzymatic capacity of S. aureus was not directly responsive to continued decrease in light intensity. The capacity of S. aureus to undergo liquid holding recovery (LHR) occurred at 23-25° (not at 11-12° or 35-37°), whereas E. coli underwent LHR at 11-12° and 23-25° but not at 35-37°. The LHR response of S. aureus was somewhat more effective than E. coli and did not show the direct response to increased liquid-holding period as did E. coli.