Fig. 1

Schematic representation of the mechanisms of extracellular and intracellular biosynthesis of MtNPs. Extracellular biosynthesis of MtNPs carried out by trapping metal ions on the cell wall and reducing them in the presence of secreted enzymes or metabolite. In the intracellular biosynthesis of MtNPs, after transfer of metal ions into cell cytoplasm, the metal ions are reduced as a result of metabolic reactions with enzymes, such as nitrate reductase