Extracellular DNA (eDNA) is present in significant concentrations in soil and water systems where nanoparticles (NPs) are ubiquitous. The incidence of NPs in natural environments is further increasing due to the release of engineered nanomaterials used in consumer products and agricultural applications. We studied the association of eDNA and NPs to differentiate the role of NPs in regulating the fate and transport of eDNA as compared to other widely studied environmental particles, such as clays. eDNA fragments isolated from antibiotic resistance genes (ARGs) were incubated in mixed batch systems with kaolinite or silica NPs. eDNA adsorbed to kaolinite, according to the Langmuir model. eDNA attached to silica NPs only when these particles were functionalized with humic acid, according to the Freundlich model of adsorption, and to a lesser extent than kaolinite. The addition of natural organic matter, increased hardness, small DNA size and single stranded conformation were favorable conditions for eDNA-NP attachment. GC content did not have a significant effect. FTIR spectra showed that eDNA’s conformation differentially changes when attached to NPs or kaolinite.  This work also examined the role of NP attachment in regulating eDNA’s persistence. eDNA fragments isolated from ARGs were exposed to varying pH conditions and DNase I concentrations. Exposure was tested in mixed batch systems with and without kaolinite and humic acid functionalized silica NPs (HASNPs). Quantity and quality of eDNA post-exposure was determined via qPCR and automated gel electrophoresis. HASNPs protected eDNA from breakage in extremely low pH. HASNPs protected eDNA from degradation by DNase I, but to a lesser extent than kaolinite. Smaller and single stranded fragments, which have greater adsorption capacities to HASNPs, were not better protected. DNase I also adsorbed to HASNPs, and this contributed to eDNA protection.  We establish eDNA-NP attachment in environmental systems and the ability of NPs to increase persistence of eDNA. We elucidate potential mechanisms of these phenomena. eDNA-NP attachment could have implications for the bioavailability of genetic material in natural environments and the rise of antibiotic resistance.

Association of nanoparticles with extracellular genetic material and implications for the fate of antibiotic resistance genes in environmental systems

ACS Fall 2020 Virtual Meeting

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