Photoreactivation of ultraviolet irradiated blue-green alga: Anacystis nidulans and cyanophage AS-1.

Ultraviolet (UV) inactivation and photoreactivation of Anacystis nidulans and cyanophage AS-1 was studied at different wavelengths. UV inactivation of free phage particles and one and two hour host-phage complexes (intracellular phages) were exponential. UV resistance of plaque forming units was attained at the latter phase of latent period. Black, blue and white lights were able to photoreactivate the UV irradiated A. nidulans whereas green, yellow and red lights were not. However, incubation of A. nidulans for more than 2 hours in black light resulted in loss of viability but shift to red light caused significant recovery. This suggests the involvement of two types of photoreactivation, i.e. of photoenzymatic repair of DNA and of the repair of the photosynthetic apparatus of A. nidulans.