Gold nanoparticles of different sizes and shapes find wide applications in optical devices, electronics, biotechnologies and catalysis. For their manufacture conventional synthetic methods involving a number of chemical methods are used and hence clean, nontoxic and environmentally benign synthetic technologies are being developed. Microbial resistance against heavy metal ions has been exploited for biological metal recovery via reduction of the metal ions or formation metal sulfides. Presently microorganisms such as bacteria and fungi are used to synthesize gold nanoparticles. The bacteria Rhodopseudomonas capsulata was found to successfully produce gold nanopartilcles of different sizes and shapes. Also the use of microorganisms in the synthesis of nanoparticles is an eco-friendly approach.