Jordan Goodman, Utah State University
Biological Engineering
Nanotechnology is revolutionizing imaging techniques, antibiotic therapy and cancer treatments. Nanoparticles (NPs) are also utilized in many commercial products such as sunscreens, paints, ceramics and semiconductors. Consequently, it is inevitable that NPs find their way into the environment. The effects that NPs have on agriculture and soil ecosystems are the focus of this project. Metal-oxide NPs such as ZnO are toxic to many bacterial pathogens but the beneficial root-colonizing isolate, Pseudomonas chlororaphis O6 (PcO6), has high tolerance. This bacterium represents an important group of micro-organisms that colonize plant roots improving their resilience to both abiotic and biotic stress. At sublethal dose, the ZnO NPs remodel the secondary metabolism of PcO6 in ways that could have an impact on agricultural ecosystems. Formation of antibiotic phenazines produced by PcO6 is strongly inhibited by ZnO NPs. Phenazines are important for PcO6 growth in biofilms, induction of tolerance mechanisms in the colonized plant, and antagonism of other rhizosphere pathogens. A role of NPs as a point source for soluble metal release is involved in these processes but does not explain the total effect of the NPs. The sublethal effects of the ZnO NPs on bacteria are similar to changes reported by sublethal doses of traditional antibiotics on human pathogens. These changes have a strong impact on fitness of bacterial pathogens, the most significant of which is induction of antibiotic resistance. Although many metal-containing NPs are being used in antimicrobial formulations, these alternative antibiotics too may be inducers of antibiotic resistance.