UV-C Radiatin effect on bacterial mortality and mutation as well as evaluation of various shields on UV-blockage
2006
Naderi Shahab, Mojtaba A`li
The Escherichia coli and Bacillus thuringiensis bacteria exposed to various doses of 254 nm UV – Irradiation. Effects of lowest doses, 11J/m2, and highest doses of UV – irradiation on survival of bacterial cells, evaluated. B. thuringiensis compare to that of E. coli, exhibited high level of torance against the UV – irradiation. 200 J/m2 of UV – irradiation did not have adverse effect on B. thuringiensis, however survival cells of the bacterium decreased from 260 J/m2, and at 3000J/m2 number of survival cells fall bellow Log1. In E. coli, UV – irradiation dose of 170 J/m2, decreased number of survival cells up to 5Log. Spores and micellium of Penicillium fungi, in compane to those of the bacteria, showed a high level of tolerance to UV – irradiation. At 18000 J/m2, few survival colonies of the fungi observed on solid medium. The effect of various shields on penetration of UV was investigated. Anti – UV Low Density Poly Ethylene (LDPE) and 1mm thick glass, completely prevented penetration of UV beam. However, ordinary LDPE shields, having various thicknesses, did not have significaut effect on penetration of UV beam. In this relation, 6μm LDPE did not have effect on penetration of UV beam. 88 J/m2 UV – irradiation caused mutation ion E. coli bacterium and rifampin resistant colonies achieved. However, 480 J/m2 UV – irradiation did not produce mutated B.t cells, with characteristic of disable to produce bacterial spores.
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