title: Induction of phr gene expression in E. coli strain KY706/pPL-1 by He-Ne laser (632.8 nm) irradiation.
abstract: We have observed that He-Ne laser irradiation of E. coli strain KY706/pPL-1 leads to induction of photolyase gene, phr. The magnitude of induction was found to depend on the He-Ne laser fluence, fluence rate and post-irradiation incubation period in the nutrient medium. The optimum values for fluence and fluence rate were 7x10(3) J/m(2) and 100 W/m(2), respectively, and the induction of phr gene was observed to saturate beyond an incubation period of approximately 2 h. Experiments carried out with singlet oxygen quenchers and with D(2)O suggest that the effect is mediated via singlet oxygen. Photoreactivation studies carried out after UVC exposure of both the He-Ne laser-exposed as well as unexposed cells showed a larger surviving fraction in the He-Ne laser pre-irradiated cells. This can be attributed to He-Ne laser irradiation-induced induction of phr expression. However, since even without photoreactivating light He-Ne laser pre-irradiated cells show higher survival against UVC radiation it appears that He-Ne laser irradiation induces both light-dependent as well as dark DNA repair processes.
authors.affiliation: Laser Programme, Centre for Advanced Technology, 452013, Indore, India.
authors.forename: R
authors.initials: R
authors.lastname: Kohli
authors.forename: B
authors.initials: B
authors.lastname: Bose
authors.forename: P K
authors.initials: PK
authors.lastname: Gupta
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D004260:DNA Repair / Q000528:radiation effects; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015870:Gene Expression / Q000235:genetics / Q000502:physiology / Q000528:radiation effects*; D006371:Helium; D007834:Lasers; D009356:Neon; D010879:Piperazines / Q000494:pharmacology; D026082:Singlet Oxygen / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019810:Sodium Azide / Q000494:pharmacology; D014466:Ultraviolet Rays; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D010879:Piperazines; C085800:modF protein, E coli; D026082:Singlet Oxygen; D006371:Helium; D009356:Neon; D019810:Sodium Azide; D001616:beta-Galactosidase; C007306:triethylenediamine