Project title: Effects of ingestion of manufactured nanoparticles on endogenous microbiota and pathogen resistance in rainbow trout

Project sponsor: NSF CBET Envrionmental Health & Safety of Nanotechnology

Project period: Nov 2014 – Nov 2017

Principal Investigators: Drs. Ted Henry, Richard Strange, Tatiana Vishnivetskaya

Postdoctoral Research Fellow: Dr Nanna Brande-Lavridsen

Project Overview: Engineered nanoparticles (NPs) are incorporated in numerous consumer products, and dramatic increases in production of NPs have led to concerns about potential and unintended adverse effects of these materials after their release into the environment. In particular, silver NPs (Ag-NPs) are used extensively due to their antimicrobial properties. Thus, chronic release of Ag-NPs into waste and surface waters is recognized as a substantial environmental concern. Ingestion of NPs is an environmentally important route of exposure, especially for fish which readily consume organisms that have accumulated NPs. Although some types of NPs are toxic in fish, the mechanisms of toxicity are not resolved, and it is possible that antimicrobial NPs can cause toxicity by altering digestive system physiology. Changes in digestive system physiology include direct damage to the epithelial mucosa, disruption of mechanisms for nutrient absorption, and changes in the structure of endogenous symbiotic microbial communities. These changes in digestive system physiology, especially alterations in the microbiome, may lead to immunosuppression and an increased opportunity for pathogen infection via the digestive tract.

The goal of this project is to measure the effects of manufactured NPs on the microbiome in the environmentally relevant, commercially significant, and scientifically important rainbow trout Oncorhynchus mykiss. The following hypotheses will be tested: 1) dietary NPs influence endogenous microbiota and digestive system physiology in fish leading to negative effects on overall fish health, and 2) NP-induced changes in endogenous microbiota enhance fish susceptibility to infection and incidence of enteric redmouth disease in rainbow trout after exposure to the bacterial pathogen Yersinia ruckeri. The effects of dietary exposure to NPs (metal NPs and carbon NPs) with appropriate bulk controls on the intestinal microbial communities will be determined by global genomic sequencing of the microbial communities and quantitative PCR to target specific microbial species of interest. Changes in abundance of specific microbes of interest will be evaluated among treatments and over time.  In the same fish, gene expression profiling will be conducted to identify biomarker genes that respond to alterations in the microbial community composition. A subset of NP treatments will be selected to conduct longer-term exposure (eight weeks) in fish that will subsequently be exposed to Y. ruckeri and the outcome of this bacterial challenge will be evaluated.

Intellectual Merit: The primary goal of this project, linking NP effects on host-microbiome interactions in fish and changes in fish physiology and pathogen response, has broad implications for humans and other animals as these fundamental interactions are conserved across all vertebrates. Results of these experiments will provide information that is directly useful for determining the effects of NPs on environmental health and subsequent risk assessments. In addition, data obtained on the rainbow trout microbiome and gut physiology will advance knowledge and provide resources for further studies of host-microbiome interactions and rainbow trout physiology. Data from this study will be available on publically accessible websites and peer-reviewed publications.

Broader Impact: This project will contribute to a growing body of scientific literature that indicates that host microbiome interactions are critical to maintaining overall organism health, fitness, and protection from infectious pathogens. Ingestion of NPs is an environmentally important route of exposure in fish, humans, and other organisms so the proposed research will provide important new information on the consequences of NP ingestion relevant to all organisms. Data obtained from the proposed investigations can be used to assist both industry and regulators to devise strategies to formulate NPs with lower toxicity or lead to regulations to reduce exposure of humans and wildlife to NPs. Training is an important component of this project and students at all levels (high school students, undergraduates, and the Postdoctoral Research Felllow responsible for conducting experiments) will learn techniques in environmental nanoscience that will enable them to make significant contributions to this important emerging discipline in the future.