Microbial melanin physiology under stress conditions and gamma radiation protection studies

Publication date: Available online 7 May 2019Source: Radiation Physics and ChemistryAuthor(s): Heba A. El-Bialy, Mammdoh S. El-Gamal, Mohamed A. Elsayed, H.A. Saudi, M.A. KhalifaAbstractAny life-threatening alteration in environmental circumstances from the optimal imposes stress on an organism. Microorganisms possess various strategies, including pigment production, to resist stress conditions in their surrounding environments. In the present study, yeast form of fungus Aureobasidium pullulans either melanized or albino was exposed to different stresses, such as salinity and antifungals (fluconazole, itraconazole, and terbinafine) as well as gamma irradiation. Results revealed that at 800 μg/ml or less of antifungal terbinafine, a positive impact was achieved on the viability of A. pullulans yeast cells, in the cultivation medium wasn't supplemented with melanin precursor (L-3,4 dihydroxyphenylalanine; L-DOPA). This enhancement in the growth yield was accompanied by increases in both internal and external melanin yields by eight and six folds, respectively. In addition, melanin is synthesized during terbinafine stress in a pathway independent from L-DOPA, but based on the excess of acetyl-CoA to tolerate squalene accumulation by feedback inhibition. Moreover, the melanized yeast cells show greater viable stability against gamma irradiation as well as pigment productivity than albino cells. The main objective of this study is to create new composites to use them as shieldi...
Source: Radiation Physics and Chemistry - Category: Physics Source Type: research