Abstract
Shewanella oneidensis MR-1, a bioelectricity generating bacterium, is broadly used in bioremediation, microbial fuel cell and dissimilatory reduction and recovery of precious metals. Herein, we report for the first time that photo induction as a trigger to stimulate gold nanoparticles (Au@NPs) formation by MR-1, with wavelength and light intensity as two key variables. Results indicated that sigmoidal model is the best fit for Au@NPs formation at various wavelengths (with R2 > 0.97). Light intensity in terms of photosynthetic photon flux density (PPFD) critically influences the rate constant in the low-light intensity region (PPFD < 20), while wavelength controls the maximum rate constant in the high-light region (PPFD > 20). By deletion of Mtr pathway genes in MR-1, we proposed the mechanism for light induced Au@NP formation is the excitation effect of light on certain active groups and extracellular polymeric substances (EPS) on the cell surface. Also, the release of electrons from proteins and co-enzyme complexes enhance electron generation. To the best of our knowledge, this is the first-attempt to explore the effect of photo-induction on Au@NPs production by MR-1, which provides an alternative cost-effective and eco-friendly process in green chemical industry.
Highlights
Gold nanoparticles (Au@NPs) are widely used in biomedicine and various biotechnological applications due to their unique magnetic and optoelectronic properties, quantum size effect and biocompatibility
S. oneidensis MR-1was first isolated from Oneida Lake, New York (Myers and Nealson 1988) and was reported to generate a trigger to stimulate gold nanoparticles (Au@NPs) in the range of 2 to 50 nm[16]
We report for the first time the mechanism for Au@NPs formation via accumulation of photons (PPFD) based on light intensity and wavelength
Summary
Gold nanoparticles (Au@NPs) are widely used in biomedicine and various biotechnological applications due to their unique magnetic and optoelectronic properties, quantum size effect and biocompatibility. This flexibility has high potential for applications as transistors, oscillators, in catalysis[1], and has even received particular interest in biosensors, drug delivery, and as therapeutic agents[2]. It is acidophilic, and can survive under high concentrations of heavy metal ions aided by a specific mechanism called extracellular electron transport (EET). The effect of light intensity and wavelength of light on Au@NPs synthesis by wild type and mutant strains (deletions of Mtr pathway genes like mtrA, mtrB, mtrC, and cymA) of S. oneidensis MR-1 has been investigated. The possible mechanism for photo-induction of Au@NPs by Shewanella has been explored
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