Due to their antimicrobial effectiveness and the increase of antibiotic resistant microorganisms, many novel approaches to medical care now rely on silver nanoparticles (AgNPs). They can be infused into bandages to treat burns and chronic wounds, and implanted medical devices are sometimes also coated with AgNPs. The number of consumer products containing AgNPs is ever on the rise and they are incorporated into items such as washing machines and refrigerators, countertops, fabrics, and toys. Despite evidence of growing microbial resistance against metal ions, and silver-resistant bacteria in particular, there is currently limited information available regarding the differences in toxicity and resistance mechanisms between ionic silver and AgNPs. It is believed that the mode of toxicity is similar between AgNPs and ionic silver, but it is unclear whether resistance mechanisms differ based on the type of silver exposure; recently Kang et al (2014) showed that E. coli-produced extracellular polymeric substances provide protection against ionic silver by forming a reducing environment within a permeability barrier. The objective of this study was to identify bacteria that exhibit variances in growth during exposure to ionic silver and AgNPs and identify their transcriptomic differences.Fourteen phenotypically different silver-resistant bacteria were isolated from the North Durham Water Reclamation Facility (Durham, NC). These strains were identified by 16S sequencing and their growth was characterized in the presence of 0, 2 and 10 ppm ionic silver and AgNPs (citrate and gum arabic coatings). From these, two strains were selected for further transcriptomic characterization. Experiments are currently underway; dissolved silver profiles are being produced via ICP-MS, and MiSeq Illumina technology is being employed to elucidate genes of interest and possible differential mechanisms of resistance between ionic silver and AgNP exposures.

Comparing ionic silver toxicity and resistance to gum arabic and citrate coated silver nanoparticles in silver resistant wastewater bacteria

248th National Meeting (2014)

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