Despite many medical advances, antibiotic resistant bacteria increasingly plague the modern world, necessitating discovery of new antibiotics. One area of nature that can provide inspiration for antibiotics is antimicrobial peptides. Many of these peptides exist in nature, with some classes that have not been studied or characterized well. One such class is the defensin-like peptides generated by the plant Medicago truncatula as part of their symbiotic relationship with Sinorhizobium meliloti. Nodule-specific Cysteine Rich (NCR) peptides are defined by the presence of multiple cysteines, and regulate the growth of S. meliloti within plant cells. While some of these NCR peptides have been shown to have antimicrobial properties, hundreds of peptides remain uncharacterized. We have developed an assay for further characterization of these peptides in E. coli. Of the seven peptides that have been tested using this assay, three have exhibited definitive antimicrobial properties against both E. coli and S. meliloti. Additionally, we have developed a system for discovering novel antimicrobial peptides. This platform, called PepSeq, uses the expression of random peptides in E. coli combined with deep sequencing to detect antimicrobial activity. This technology is capable of screening through millions of peptide molecules simultaneously. Using this platform, we have discovered and confirmed six novel antimicrobial peptides, with hundreds of additional predicted antimicrobial peptides. In addition to the peptides we have analyzed using PepSeq, additional peptide scaffolds could be used to discover more potent antimicrobial peptides.



College and Department

Life Sciences; Microbiology and Molecular Biology



Date Submitted


Document Type



antimicrobial peptide, NCR peptide



Included in

Life Sciences Commons