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Mutation Research, 49 ( 1 9 7 8 ) 1 3 3 - - 1 3 7 © E l s e v i e r / N o r t h - H o l l a n d B i o m e d i c a l Press

Short communication BIOLOGICAL EVIDENCE F O R THE DESTRUCTION OF THE P H O T O R E A C T I V A T I O N ENZYME BY 365 nm RADIATION IN ESCHERICHIA COLI *

M I C K E Y S. B R O W N

Division of Biological and Medical Research, Argonne National Laboratory Argonne, Ill. 60439 (U.S.A.) ( R e c e i v e d 22 April 1 9 7 7 ) ( R e v i s i o n received 9 A u g u s t 1 9 7 7 ) (Accepted 1 September 1977)

The destruction of the PRE by 365-nm radiation has been demonstrated chemically both in vivo and in vitro in Escherichia coli and E. coli DNA [3,9]. Recent studies have shown that under appropriate conditions some UV~ensitire strains of bacteria irradiated by 365-nm radiation can be strongly photoreactivated [3,9,11]. The combination of chemical and biological evidence presented in these papers support our earlier proposal [9,11] that pyrimidine dimers are an important lethal lesion involved in inactivation at this near-UV wavelength (365 nm) on recA and recA uvrA strains and that the PRE is damaged to a biologically significant degree b y 365-nm radiation, particularly at the higher fluence levels. The bacterial strain used in this study was E. coli B/r Hcr (uvrA thy trp) (from D. Billen's laboratory -- a derivative of E.M. Witkin's E. coli WP2s strain, also referred to by some authors as WP2 Hcr) [9], a UV-sensitive strain unable to excise pyrimidine dimers. Survival curves were obtained using stationaryphase cells grown on nutrient agar at 37°C for 48 h. Exponential-phase cells were grown in nutrient broth at 37°C for 24 h, then diluted 1 : 10 with fresh nutrient broth, and allowed to grow an additional 3 h at which time the concentration of cells was approximately 2 × 10 ~ cells/ml. Both stationary-phase and exponential-phase cells were washed and resuspended with M9 salts buffer [2] to a concentration of approximately 107 cells/ml before irradiation in cuvettes with an internal diameter of 1 cm made of quartz (for 254 nm) or pyrex (for 365 or 405 nm). During irradiation (254 and 365 nm only) the cells were kept evenly suspended and aerated with forced moist air i n t r o d u c e d through a capillary tube affixed to the b o t t o m of each vessel. Stationary-phase By acceptance of this article, the publisher or recipient acknowledges the U.S. Government's right to retain a nonexclusive, royalty-free license in and to any copyright covering the article. * Work supported by the U.S. Energy Research and Development Administration.

Abbreviations: PR, photoreactivation; PRE, photoreactivating enzyme.

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Biological evidence for the destruction of the photoreactivation enzyme by 365 nm radiation in Escherichia coli.

133 Mutation Research, 49 ( 1 9 7 8 ) 1 3 3 - - 1 3 7 © E l s e v i e r / N o r t h - H o l l a n d B i o m e d i c a l Press Short communication BI...
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