Influence of outer membrane c‐type cytochromes on particle size and activity of extracellular nanoparticles produced by Shewanella oneidensis

Abstract

The metal-reducing bacterium Shewanella oneidensis is capable of reducing various metal(loid)s and produces nanoparticles (NPs) extracellularly, in which outer membrane c-type cytochromes (OMCs) have been suggested to play important roles. The objective of this study was to investigate the influence of the OMCs, that is, MtrC and OmcA, on the size and activity of the extracellular silver NPs (AgNPs) and silver sulfide NPs (Ag(2)S NPs) produced by S. oneidensis MR-1. We found that (i) the lack of OMCs on S. oneidensis cell surface decreased the particle size of the extracellular biogenic AgNPs and Ag(2)S NPs; (ii) the biogenic AgNPs from the mutant lacking OMCs showed higher antibacterial activity; and (iii) the biogenic Ag(2)S NPs from the mutant lacking OMCs exhibited higher catalytic activity in methylviologen reduction. The results suggest that it may be possible to control particle size and activity of the extracellular biogenic NPs via controlled expression of the genes encoding surface proteins. In addition, we also reveal that in extracellular biosynthesis of NPs the usually neglected non-cell-associated NPs could have high catalytic activity, highlighting the need of novel methods that can efficiently retain extracellular NPs in the biosynthesis processes.

Disruption of Putrescine Biosynthesis in Shewanella oneidensis Enhances Biofilm Cohesiveness and Performance in Cr(VI) Immobilization

“…A 1.6-ml outlet sample was filtered through a 0.22-m syringe filter and mixed with 0.2 ml of 0.5 g/liter s-diphenylcarbazide in 10% methanol-12.5 mM H 2 SO 4 followed by OD 540 measurement after a 20-min incubation. At the end of the Cr(VI) immobilization experiment, a portion of the biofilms in the reactors was analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) (34). The samples were dried and sputtered with Pt.…”

Biofabrication of gold nanoparticles by Shewanella species

“…There have been reports on the biosynthesis of metal nanoparticles using Shewanella species (Ng et al 2013;Suresh et al 2011), but the physical factors for optimization have rarely been reported. Therefore, it is critical and meaningful to explore the optimal conditions of Au@NP biofabrication by SXM and MR-1.…”

“…In the MR-1 strain, the outer membrane c-type cytochromes, MtrC and OmcA, were considered as important proteins for metal reduction (Wu et al 2013a). However, the MR-1 wild type and its mutants omcA and mtrC were still capable of reducing Au 3+ into Au@NPs (Wu et al 2013b), while the particle size of the extracellular nanoparticles were decreased mtrC and omcA mutants (Ng et al 2013). On the other hand, Shewanella xiamenensis, which is isolated from coastal sediment collected off Xiamen, China, is a close-related strain to S. oneidensis based on phylogenetic tree analysis by 16S rRNA and gyrase gene (Huang et al 2010).…”

Investigation Concerning the Formation Process of Gold Nanoparticles by Shewanella oneidensis MR-1

“…Primarily, a final redox reaction that proceeds through MtrC and OmcA have important roles in the reduction of various metal ions, including Pd(IV), U(VI), Ag(I), and Fe(III). 1,[13][14][15] Previous studies showed that the reduction of Au(III) ion to gold nanoparticles (Au NPs) was successfully performed using S. oneidensis, and that Au NPs were produced on the bacterial surface. 2,16 However, the contribution of the bacterial surface structure to the production of Au NPs remained unclear.…”