Nanotechnology is a highly energized discipline of science and technology. One of the major challenges of nanotechnology is the synthesis of nanomaterials with a wide range of chemical compositions and sizes. Moreover, the ability to scale up
synthesis strategies for low-cost, large-scale production is an important factor. Thus, there is a need for developing  eco-friendly means of nanoparticle synthesis and the use of microorganisms for this purpose is an emerging area. In this paper, a marine culture of Bacillus sphaericus isolated from the west coast of India has been used to synthesize silver nanoparticles. Bacillus sphaericus is grown in Zobell marine broth and cell lysate prepared by suspending the cells in distilled water. When silver ions are added to the cell lysate, they are reduced to silver nanoparticles. The time required for silver reduction is drastically reduced if the solution is exposed to light. Optical absorption, X-ray diffraction, TEM, and energy dispersive analysis of X-rays showed that the silver particles were in the nanoregime. Reduction of silver appears to be mediated by non-specific cellular constituents. These findings open up several new possibilities of obtaining silver nanoparticles in an economical and environmentally acceptable manner, on a large scale.