ACTION SPECTRA IN THE VACUUM UV AND FAR UV (122-300 NM) FOR INACTIVATION OF WET AND VACUUM-DRY SPORES OF STREPTOMYCES-GRISEUS AND PHOTOREACTIVATION

Inactivation and photoenzymatic repair were studied in spores of Streptomyces griseus irradiated with monochromatic UV light (bandwidth, 2 nm) in the range 200-300 nm in the wet state or 122-300 nm in the vacuum-dry state. In vacuum, the spores are about twice as UV resistant than under wet conditions. In the UV region 220-300 nm, the action spectrum conforms to the DNA absorption spectrum. In the vacuum UV, it deviates from DNA absorption, passes a minimum at 190 nm and increases sharply towards shorter wavelengths; photoreactivation is absent. It is suggested that absorption by cellular components other than DNA becomes important. In the far UV, the photoreactivable sector is higher in spores irradiated in the wet state than in those irradiated in vacuum. It is postulated that, in the vacuum-dry state, DNA photoproducts other than cis-syn-pyrimidine dimers are relevant to lethality.