Bioaccumulation of gold by filamentous cyanobacteria between 25 and 200°C

Plectonema boryanum UTEX 485 was reacted with aqueous AuCl4- solutions (similar to 2 mM Au) at 25 to 100 degrees C for 1 month, and 200 degrees C for one day. Addition of AuCl4- to cyanobacteria killed the cultures instantly, and Au was precipitated throughout the cells as nanoparticles. Precipitation of octahedral crystal platelets of Au occurred in the aqueous fluid, with particle size increasing with increase in temperature from about 1.5 mu m at 25 degrees C to 10 mu m at 100 degrees C. Addition of AuCl4- to suspensions of the dead, autoclaved cyanobacteria also precipitated Au from solution, suggesting that the presence of cell degradation products caused instability of AuCl4-.