 This study assessed the ability of selected strains of cyanobacteria and microalgae to produce silver nanoparticles, AGNPS. The results indicated that AGNPS could be produced from both living and dead cells, suggesting that the process involved an extracellular compound such as polysaccharides. TEM analysis revealed that the nanoparticles had different shapes and sizes, with the smallest being around 13 nanometers and the largest being around 31 nanometers. The antibacterial activity of AGNPS was confirmed in all but one strain of cyanobacterium, lindithrix sp. February 1, 37, which formed the largest particles. This article was authored by V.J. Patel, David Berthold, Praveen Paranic, and others.