Metabolic changes in Phycomyces blakesleeanus mycelia during selenite reduction and cellular localization of synthesized SeNPs.

This study considers the capacity of fungus Phycomyces blakesleeanus for removal of toxic selenite from the environment and metabolic response of the mycelium during Se transformation. The X-ray Fluorescence Microscopy (XFM) suggests two pathways of selenite transformation: extensive internalisation and intracellular transformation leading to volatilization, and synthesis of SeNPs at the cell surface, with the contribution of each pathway depending on selenite concentration and treatment duration. Glutathione plays an important role in the reduction process, as the glutathione pool is alternately removed from and restored to redox balance during Se treatment. Enzymes facilitate the maintenance of the cellular redox balance, which is reflected in an increase in the specific activities of glutathione reductase, glutathione peroxidase, glutathione S-transferase and catalase at different time points during the 48-h exposure of mycelia to 100 µM selenite. During the transition from the exponential to the stationary growth phase, a metabolic shift was documented, which can be seen in the change of the total glutathione content and glutathione redox status. This points out that the developmental stage of the mycelia plays an important role in the capacity for selenite reduction and mycelia survival in a selenium-enriched medium. This work is a step towards the use of selenite-contaminated media for Se extraction and re-utilisation and suggests that Phycomyces blakesleeanus might be a suitable organism for the effective re-utilisation of Se.