Effect of UV-C on biochemical markers of the radiotrophic fungus Alternaria alternata

Life on Earth exists within a continuous flow of radiation. As compared to the other living organisms fungi interact with radiation in a different way that allows them to withstand high levels of natural or man-made ultraviolet (UV-C) or ionized radiation. Ten years after 1986 Chernobyl disaster, it was discovered that black fungi could grow on the damaged reactor walls which were highly reactive and the research studies on these extreme organisms started. 37 species and 19 genera have been detected in the micobiota isolated from Chernobyl reactors and Alternaria alternata, that was used in our study, was among this micobiota. A comparison between species within Chernobyl micobiota has revealed that, melanin containing species dominated heavily contaminated sites. Melanin is an enigmatic pigments found in all kingdoms of life has a variety of roles and functions. Melanin protects the organisms from low/ high temperatures, radiation, chemical stress (heavy metal and oxidizing agents) and biochemical stress; bonds with various drugs and chemicals and acts as a camouflage. Besides this, melanin functions as an energy transducer and shows high antioxidant properties. It leads to a decrease in the amount of reactive oxygen species in the cell and this gives resistance to the organisms under extreme environmental conditions. By acting as an electron acceptor, bonding with some enzymes such as peroxidase or prevent hydrolysis of water and using many different mechanisms, melanin inhibits radical formation. Because of all these melanin is the essential component in this research study. Literature does not provide enough research on reactive oxygen species that are induced by UV-C, the effects of UV-C on radiotrophic fungi and its cellular defense mechanisms, and its antioxidant systems that are responsible for reactive oxygen species scavenging. Within the study three groups of A. alternata have respectively been exposed to the procedures of an inoculation; nine days of incubation and an addition tricyclazole (Tc) fungicide which is a melanin synthesis inhibitor. After these fungal cultures have been exposed to certain doses of ultraviolet C and their enzymes activation and glutathion level has been observed. As a result of this study, we have determined that the production of melanin has a synergistic effect on antioxidant enzymes. Moreover, it has been found that due to its antioxidant activity in cells, melanin contributes to antioxidant defense system via collaborating with enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and glutathione reductase (GR). KEYWORDS: Alternaria alternata, melanin, UV-C radiation, trcyclosol, oxidative stress, catalase, glutathione reductase, superoxide dismutase, glutathione S- transferase.