Action Spectra for Photoreactivation of Ultraviolet-irradiated Escherichia Coli and Streptomyces Griseus

Action spectra for photoreactivation (light-induced recovery from ultraviolet radiation injury) of Escherichia coli B/r and Streptomyces griseus ATCC 3326 were determined. The spectral region explored was 365 to 700 mmicro. The action spectrum for S. griseus differed from that for E. coli, indicating that the chromophores absorbing reactivating energy in the two species were not the same. Reactivation of S. griseus occurred in the region 365 mmicro (the shortest wave length studied) to about 500 mmicro, with the most effective wave length lying near 436 mmicro. This single sharp peak in the spectrum at 436 mmicro suggested the Soret band typical of porphyrins. Reactivation of E. coli occurred in the region 365 to about 470 mmicro, with the most active wave length lying near 375 mmicro. The single, non-pronounced peak near 375 was probably not due to a Soret band, and the identification of the substance absorbing reactivating light in E. coli is uncertain. In neither species was the region 500 to 700 mmicro active. The implications of these action spectra and their differences are discussed.