The need for environmental control of microbial growth is paramount to proper function of engineered systems. Microbial growth in cooling towers, distribution systems, and food production decrease efficiency and place the public’s health at risk. Combating these problems is complicated due to the limited materials that are both able to limit microbial growth and are not harmful to human and environmental health. Recently, silver nanoparticles have seen increased research focus as a means to combat microbial growth in engineered systems; however, they are sensitive to ligands, such as chloride, sulfide as well as solution state characteristics such as ionic strength. In the following study, we show that chloride and ionic strength directly impact the toxicity of silver nanoparticles through aggregation state features, fractal dimension and hydrodynamic radius, likely changing the surface interaction of silver nanoparticle aggregates with bacterial surfaces. Further, we find that these changes impact the expression of a stress response gene, KatE, a catalase that limits oxidative stress and is largely dependent on ionic strength. Lastly, we show that in low ionic strength conditions, low fractal dimension aggregates form that increase the toxicity of silver nanoparticles while stimulating a physiological adaptation in <i>Pseudomonas aeruginosa</i>, resulting in increased antibiotic resistance. A subsequent knock out study indicates that these adaptations might be linked to the expression of multidrug efflux pumps. In total, these data indicate that the physical and chemical aquatic environment might be useful in controlling toxicity and interactions that lead to increased antibiotic resistance.

Aqueous chloride concentrations and ionic strength control silver nanoparticle toxicity in <i>Pseudomonas aeruginosa</i> thereby increasing stress response and antibiotic resistance

255th National Meeting (2018)

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Aqueous chloride concentrations and ionic strength control silver nanoparticle toxicity in Pseudomonas aeruginosa thereby increasing stress response and antibiotic resistance