(597d) Utilizing Native Metabolic Pathways in Deinococcus Radiodurans for Metallic Nanoparticle Biosynthesis

There has been considerable interest in the biosynthesis of metallic nanoparticles for applications in green chemistry, bioremediation, catalysis, and as antimicrobials. This field has prompted the investigation of a diverse range of organisms as nanoparticle production hosts, but is limited by the lack of knowledge of precise molecular mechanisms and inability to control nanoparticle size and morphology. Deinococcus radiodurans is a bacterium that has gained interest for bioremediation purposes due to its high tolerance to radiation, metals, and other forms of oxidative stress. As such, this organism has been shown to produce silver and gold nanoparticles. In this study, we present how the use of metal-induced environmental stresses has enabled cell-free production of bimetallic nanoparticles as well as the tuning of nanoparticle yield and morphology in D. radiodurans. To shed light into the biosynthetic mechanism of nanoparticle formation in D. radiodurans, which is currently poorly understood, we have created genetic knockouts of several oxido/nitroreductases using homologous recombination; these reductases have been identified in other bacteria as key for silver nanoparticle formation. We also tested sRNA knockout strains of sRNAs that have been shown to be relevant to oxidative stress since metals can promote this type of cellular stress. Using UV/vis spectroscopy and TEM, our results show that some of these factors have a significant influence over the rate of nanoparticle biosynthesis or nanoparticle morphology that is comparable to the role of reductases, suggesting promising new engineering targets. This work provides greater insight into the multitude of factors that perhaps contribute to metal reduction pathways and nanoparticle biosynthesis as part of a larger general bacterial stress response.