engleski

ADAPTIVE RESPONSE OF Aspergillus flavus NRRL 3251 TO ILLUMINATION

Environmental factors which may act as modulators of oxidative stress in fungi are ultraviolet (UV) and visible light (VIS). The increased production of reactive oxygen species (ROS) in turn causes an adaptive cellular response including upregulated antioxidant enzyme activity or cell death due to ROS overproduction. Effects of UV and/or VIS light on Aspergillus species reported in the literature are contradictory. Therefore, to clarify the effect of the visible light on A. flavus during submersed growth we examined the effect of VIS illumination. The biomass yield, activities of antioxidative enzymes (Cu, Zn-SOD, Mn-SOD, CAT, GPx), level of thiobarbituric acid reactive substances (TBARS), and reduced/oxidised glutathione ratio (GSH/GSSG ratio) were determined over the course of 168 hours of cultivation. Illumination decreased biomass yield, GSH/GSSG ratio, TBARS content, CAT and GPX activities, but increased Cu, Zn-SOD activity. The exposure of A. flavus NRRL 3251 to the visible light during 168 hours of submersed growth causes adaptive response of fungi by modulation of cellular antioxidants. It is known that light is inducer of ROS (e.g. singlet oxygen), and these can participate in the mycotoxin-related inter cell signal transmission. The modification of cell signal transmission can also effect the expression of antioxidative enzymes (downregulation up to maximum 65%), with exception of Cu, Zn-SOD (upregulation up to maximum 50%) due to its place of activity within cytoplasm. The exact molecular mechanism is to be established in the future.

Aspergillus flavus; VIS illumination; oxidative status

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