The interaction of cyanobacterial biomass (Plectonema boryanum UTEX 485) with aqueous palladium(II) chloride (PdCl2 degrees) has been investigated at 25-100 degrees C for up to 28 days. We report that the release of organic materials from the cyanobacteria promoted the precipitation of Pd(0) as crystalline spherical and elongate nanoparticles (<= 30 nm), both in solution and as dispersed and encrusted nanoparticles on cyanobacterial cells. In contrast, under abiotic conditions at 100 degrees C, palladium hydride (PdHx,) was the principal palladium phase precipitated, with only minor amounts of palladium metal.