The Use of Gamma Irradiation in the Sterilization of Streptomyces Colonizing the Tempra Paintings in Ancient Egyptian Tombs

Abstract

Eight out of forty six Streptomyces strains from mural paintings at the Tell Basta and Tanis tombs were exposed to increasing doses (5, 10, 15, 20, 25kGy) of gamma irradiation. These strains varied in their resistance profile. S. canarius was the most resistant to gamma irradiation doses, as it was totally eliminated at 25kGy, whereas S. chibaensis and S. albidofuscus resisted to 20kGy and S. ambofaciens resisted 15kGy. The other strains under investigation showed a lower resistance to gamma irradiation. Tricyclazole (5, 7, 10 µg/mL) inhibited melanin production after gamma irradiation at doses lower than lethal dose. Gamma irradiation with the previous doses enhanced the chitinease activity of irradiated Streptomyces strains, but S. canarius was the exception. No color change was observed either for pigments or for binding media, after gamma irradiation at the same doses.

Keywords

• gamma irradiation
• melanin
• mural paintings
• streptomyces
• tricyclazole