Abstract
The exposure of Salmonella typhimurium to environmentally relevant near-UV light stress has been studied by the use of a low-intensity, broad-band light source. The exposure of cells to such a light source rapidly induced a growth delay; after continuous exposure for 3 to 4 h, cells began to die at a rapid rate. The oxidative defense regulon controlled by the oxyR gene was involved in protecting cells from being killed by near-UV light. This killing may be potentiated by the overexpression of near-UV-absorbing proteins. These results are consistent with near-UV toxicity involving the absorption of light by endogenous photosensitizers, leading to the production of active oxygen species. We have shown, however, that one such species, H2O2, is not a major photoproduct involved in killing by near-UV light. Strains lacking alkyl hydroperoxide reductase were more sensitive to near-UV light, indicating that such hydroperoxides may be photoproducts. Near-UV exposure induced sensitivity to high salt levels, indicating that membranes may be a target of near-UV toxicity and a possible source of alkyl hydroperoxides. The demonstration of the inactivation of the heme-containing protein catalase indicates that direct destruction of UV-absorbing macromolecules could be another factor in near-UV toxicity. Cells which have been exposed to near-UV light for long, but sublethal, periods of time (up to 4 h) can recover and resume growth if the UV exposure is stopped but become progressively more sensitive to further stresses, such as H2O2. This result indicates that cells gradually accumulated damage during near-UV exposure until toxic levels were reached.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference49 articles.
1. Synergistic action of near ultraviolet radiation and hydrogen peroxide on the killing of coliphage T7: possible role of superoxide radical;Ahmad S. I.;Photobiochem. Photobiophys.,1981
2. A spectrophotometric method for measuring breakdown of hydrogen peroxide by catalase;Beers R. F.;J. Biol. Chem.,1952
3. Chamberlin C. E. and R. Mitchell. 1978. A decay model for enteric bacteria in natural waters p. 325-348. In R. Mitchell (ed.) Water pollution microbiology vol. 2. John Wiley & Sons Inc. New York.
4. Positive control of a regulon for defenses against oxidative stress and some heat-shock proteins in Salmonella typhimurium;Christman M. F.;Cell,1985
5. Purification of the odianisidine peroxidase from Escherichia coli B;Claiborne A.;J. Biol. Chem.,1979
Cited by
87 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献