Photoinactivation of Propionibacterium acnes by near-ultraviolet light

Photodestruction of Propionibacterium acnes was investigated by broad-band near-ultraviolet light. The inactivation of the bacteria was found to be oxygen dependent, and without O2 practically no photoinactivation occurred. D2O caused an increased inactivation (D10 = 5 kJ/m2 in D2O as compared to D10 = 11 kJ/m2 in normal water). Decreased temperature during illumination increased the ability to form colonies. The results are compared with corresponding results for other types of cells and the destruction mechanism is discussed.