Natural marine phytoplankton assemblages from Bahía Bustamante (Chubut, Argentina, 45 degrees S, 66.5 degrees W), mainly consisting of cells in the picoplankton size range (0.2-2 microm), were exposed to various UVBR (280-315 nm) and UVAR (315-400 nm) regimes in order to follow wavelength-dependent patterns of cyclobutane pyrimidine dimer (CPD) induction and repair. Simultaneously, UVR induced ...

Kelner (1949), working with conidia of Streptomyces griseus, discovered that light belonging to the visible range is capable of reactivating biological material that has been rendered inactive by ultraviolet radiation (WJY). Shortly after Kelner's discovery was known, a similar phenomenon in bacteriophages (bacterial viruses) was observed by accident. Plates of nutrient agar containing UV-inact...

The kinetics of inactivation of mycobacteria by ultraviolet light were investigated. Mycobacterium tuberculosis and M. marinum were shown to be capable of photo-reactivation.

Hemophilus influenzae-transforming DNA, which has been inactivated by ultra-violet radiation, is reactivated by visible light in the presence of a cell-free extract of Escherichia coli B. The time rate of reactivation is increased by increasing the E. coli extract concentration, the temperature, and the intensity of illumination. Only DNA containing an ultraviolet-damaged genetic marker exhibit...

During investigations on the role of bacterial pigments in ultraviolet irradiation damage and in photoreactivation, several agents were tested as suppressors of pigmentation effects. Chromobacterium violaceum is extremely radiosensitive in that it shows very high inactivation by ultraviolet and also high photorecovery with white light. Sodium azide depresses both of these effects significantly....

Ultraviolet-inactivated Hemophilus influenzae transforming DNA recovers its activity when mixed with cell-free extracts of bakers' yeast and exposed to visible light. The active agent in the extract is not used up in the reaction, and purification has not separated it into more than one non-dialyzable component. It differs from the agent in Escherichia coli extract, which produces very similar ...

Zelle and Hollaender (1955) summarized data from several sources which showed that spores of aerobic bacilli are usually about twice as resistant to killing by ultraviolet light as are vegetative cells of the same species. Recently Stuy (1956) showed that spores of Bacillus cereus are many times more resistant than their vegetative cells. In seeking an explanation for the discrepancies in these...