Formation of biologically influenced palladium nano/microstructures and resulting limitations of metabolic functions by Desulfovibrio species

Abstract

A wide range of bacteria is known to be capable of synthesizing metallic nanoparticles. One such bacterium, Desulfovibrio desulfuricans, can reduce palladium ions to elemental palladium (Pd) and form nanoparticles that attach to the surface of the cells. Previous research has been concerned with utilizing this ability as an innovative method for the production of precious metals, but the impact of these surface associated metallic nanoparticles on bacterial metabolism has not previously been investigated. In addition, the amount of Pd that a microbe can reduce in this manner has also not been explored. Desulfovibrio species can exist as members of the microbial community inside low carbon steel oil and gas pipelines and play a role in internal microbially influenced corrosion as a result of the production of hydrogen sulfide from sulfate reduction and the oxidation of steel. This study demonstrates the remarkable extent to which Desulfovibrio desulfuricans and Desulfovibrio ferrophilus IS5 can be coated with locally generated metal nanoparticles, with individual cells carrying more than 100 times their mass of palladium metal. The effect of metal coating mass on metabolism and replication for a wide range of loadings is also studied, revealing that Desulfovibrio spp. are unable to utilize sulfate for iron oxidation at a specific threshold which further prevents the formation of corrosive sulfide. This work also demonstrates for the first time that the Desulfovibrio spp. studied are capable of self assembling a variety of structures through metal reduction, forming unique biological-palladium scaffolds. Furthermore, D. ferrophilus IS5 rapidly produces microbial nanowires in response to palladium reduction, interlinking with neighbouring bacterial cells. This further adds to the complexity and range of potential self assembled nanomaterials. These findings offer a new method for preventing internal pipeline corrosion and a novel approach to self-assembled materials.