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Title: Plant endophytes as novel sources of antimicrobials: Characterizing fungal isolates from alfalfa

item WASS, BRITTA - St Catherine University
item Samac, Deborah - Debby
item FOSTER-HARTNETT, DAWN - St Catherine University

Submitted to: Undergraduate Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 4/3/2014
Publication Date: 4/5/2014
Citation: Wass, B., Samac, D.A., Foster-Hartnett, D. 2014. Plant endophytes as novel sources of antimicrobials: Characterizing fungal isolates from alfalfa. National Conferences on Undergraduate Research. April 3-5, 2014. Lexington, KY.

Interpretive Summary:

Technical Abstract: Microbial antibiotic resistance is increasing at alarming rates, posing a critical need for new sources of antibiotics. Many forms of antibiotics currently in use were developed from bacterial and fungal species which produce antimicrobial compounds to ward off microbial competitors. Fungal species known as endophytes live symbiotically within plants and may exhibit these characteristics. Our research goal was to identify endophytes present in alfalfa and assess antimicrobial production in vitro. We obtained alfalfa crop samples grown in Minnesota and Idaho, cultured and isolated fungal endophytes from alfalfa stem tissue, and determined isolate identity using 18S ribosomal subunit gene sequence. We evaluated isolate antimicrobial potential by first streaking fungal isolates on agar plates and then cross-streaking against those isolates with a number of test bacterial and fungal strains, including known alfalfa pathogens. Fungal isolates that exhibited inhibition of growth of the test strains may be potential antimicrobial producers, and were grown up on a larger scale, then extracted with ethyl acetate to separate out the potential antimicrobials. The ethyl acetate extracts were then used in disk-diffusion assays against test bacterial and fungal strains, measuring growth inhibition. We cultured and identified over 45 fungal isolates successfully; these represent both alfalfa pathogens and endophytes, and at least 10 of these isolates produce antimicrobial substances that inhibit bacterial and fungal species in initial screens. We are currently testing the ethyl acetate extracts with the eventual goal of identifying the chemical structure of the antimicrobial molecules. The fungal endophytes we isolated and the antimicrobials they produce may play a role in protecting alfalfa from disease, and new antimicrobial compounds could be potentially used in clinical research. Alfalfa, along with other plant species, need to be considered as likely sources for novel antimicrobials.