Interactions between hyperthermia and non ionizing radiations in Escherichia coli

It was studied in the present work the effect of the heat shock response induced before UV irradiation (254, 280, 302, 313 and 365 nm) of different E. coli strains proficient in DNA repair systems UVAR- and/or RecA-dependents and of the UVAR RecA double mutant. As the heat shock response may protect damaged proteins this property was used to correlate this response to the DNA repair enzymatic systems of UV-irradiated cells. Previous heat shock treatment increases UV survival of excision proficient strains in all wavelengths and or uvr strains in some wavelengths. Depending on the wavelength and the DNA repair mechanism, increasing survival is associated to increasing or diminishing mutant frequencies. We concluded that a mechanism like this, being induced in the cell within normal physiological conditions and environmental stimulus may lead us to think that biological systems besides being damaged by solar radiation are protected by it. (author)