Microorganisms are extremely sensitive to metals and can be exquisitely selectively. As part of their resistance to the toxic effects of metal ions some microbes reduce or mineralize the ions to limit their effect on the cell. This provides the means for us to biomanufacture metallic nanoparticles, irrespective of the source of metal ions, and synthesise new particles with novel functions. To exploit this biosynthesis, we have identified genetic elements that increase microbial nanoparticle production, change the size of the nanoparticles produced and enhance their efficiency. The approach has been demonstrated to be effective for the platinum group metals with engineered Oleidesulfovibrio alaskensis and even allows for the synthesis of nanoparticles from lab wastes. The resultant Pd nanoparticles synthesized by this sulfate-reducing bacterium catalyse a variety of coupling reactions under green chemistry conditions more effectively than chemically synthesised nanoparticles or Pd on carbon. Our research includes the first reported microbial nanoparticles to catalyse the Sonogashira reaction and the first demonstration that these biogenic catalysts can be interfaced with the products of engineered metabolism for small molecule synthesis.