Activation of antioxidative metabolism in different growth stages of Phycomyces blakesleeanus mycelia exposed to vanadate

Abstract

Understanding the effect of vanadate (V(V)) on the well-studied filamentous fungus, Phycomyces blakesleeanus, is of great importance for establishing the mechanisms of vanadium internalisation and metabolism. Although P. blakesleeanus is not a soil fungus, its short life cycle and evolutionary basal position in the fungal kingdom makes it an excellent model for studying the interactions of fungi with vanadate and other metals as well as the improvement of their use in vanadium recovery (bioaccumulation) and the remediation of contaminated soils. In this study, we investigated the effects of vanadate at three concentrations (1 mM, 5 mM, and 10 mM) on both enzymatic and non-enzymatic components of the antioxidant system of mycelia at different growth stages. The production of ROS was highest in the exponential phase, but its reducing capacity was maintained, probably due to high levels of non-enzymatic antioxidants such as phenols and glutathione. In the stationary phase, while the reducing capacity of the mycelia was somewhat impaired by vanadate (V(V)), it recovered due to the action of the glutathione system and the activation of peroxidases. In the late exponential/early stationary phase, no significant activation of the antioxidative systems was observed, and the reducing capacity was impaired. When we consider the effects of V(V) on mycelial growth, this was the only phase with reduced viability, while the exponential and stationary phases were unaffected, if not stimulated. This study provides insight into the tolerance of P. blakesleeanus mycelia to vanadate, even at concentrations as high as 10 mM, making this fungus a good candidate for V(V) bioaccumulation.