Skip Navigation
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Your Environment. Your Health.


Export to Word (
Principal Investigator: Becket, Elinne Coral
Institute Receiving Award California State University San Marcos
Location San Marcos, CA
Grant Number R15ES033027
Funding Organization National Institute of Environmental Health Sciences
Award Funding Period 05 Apr 2021 to 31 Mar 2024
DESCRIPTION (provided by applicant): Project Summary The spread of microbial antibiotic resistance (AR) is a global healthcare problem driven by the extensive clinical and agricultural use of antibiotics. Natural environments serve as massive harbors of antibiotic resistance reservoirs, known as the “resistome”. Genes that encode AR exist on mobile genetic elements and are transferred between microbes through horizontal gene transfer (HGT); this transfer can be triggered in response to antibiotic exposure. Coastal environments have increased exposure to antibiotic waste from anthropogenic inputs such as waste- and stormwater runoff, which influence the spread of AR genes from non-pathogenic microbes to human pathogens. Humans exposed to coastal waters are at increased risk of drug-resistant infections after storms or near wastewater outlets, as well as when eating seafood with antibiotic-resistant microbiomes. Elucidating the sources and patterns of AR gene transfer in environmental reservoirs in response to these runoffs is therefore of great importance. While increases in AR in response to runoffs have been established, mapping the transfer of AR genes to particular community members has yet to be established in coastal microbiomes. In this proposal, we seek to explore the changes in resistome distribution in coastal microbial populations, specifically in response to antibiotics and storm runoff, through a combination of metagenomic approaches. 1) We will employ a metagenomic chromatin conformation capture (MetaHiC) to trace the movement of mobile genetic elements and AR genes between microbial community members in response to treatment with tetracycline, an antibiotic commonly in runoff and known to induce HGT. MetaHiC can map mobile elements to particular microbial hosts, providing a detailed look at how antibiotic contamination affects resistome distribution in complex microbial communities. 2) We will combine MetaHiC data with long- read metagenomic sequencing to define the ratio in which integrative conjugative elements (ICEs, one of the main mobile genetic elements that carry AR genes) are excised or integrated in microbial genomes in response to tetracycline treatment. 3) Using MetaHiC on coastal microbiomes throughout rainstorms, we will build on preliminary data (which revealed taxonomic and resistome composition changes in response to storm runoff) to develop a profile of coastal microbes containing AR genes following rainstorms. We anticipate that a) tetracycline will induce excision and transfer of ICEs in coastal microbiomes in a non-AR gene-specific manner, b) increases in the abundance of known pathogens that are antibiotic-resistant will appear within 24-72 hours of storm runoff, c) increases in the abundance of antibiotic-resistant commensal bacteria will be observed after rainstorms, creating a resistome reservoir for clinically relevant human pathogens to use as a genetic source of AR. This research will be performed by undergraduates and will elucidate the spread of antibiotic resistance in coastal microbiomes.
Science Code(s)/Area of Science(s) Primary: 68 - Microbiome
Secondary: 03 - Carcinogenesis/Cell Transformation
Publications See publications associated with this Grant.
Program Officer Frederick Tyson
to Top