(1st Place) Directed evolution of insecticidal activity of plant growth promoting rhizobacteria (PGPRs)

Plant growth-promoting rhizobacteria (PGPR) are bacteria which reside in and/or colonize the plant rhizosphere. They are diverse bacteria from genera such as, Pseudomonas, Bacillus, Burkholderia, Azospirillum, Arthrobacter, Azotobacter, Streptomyces, Klebsiella, Enterobacter, Alcaligenes, Agrobacterium. PGPRs can produce metabolite secretions of chemicals which can promote the growth and health of the nearby plants and roots. PGPRs can aid in plant acquisition of key abiotic nutrients such as phosphorus, vital minerals, sulfur, and nitrogen which enhances plant metabolic growth and processes such as root or shoot growth. PGPRs are currently being investigated for a variety of applications involving their usage in agriculture, bioinoculants, bioformulations, nanotechnology, fertilizers, nutrient management systems, and much more. Our study aimed, for the first time, to discover and evolve novel insecticide modes of action derived from PGPRs. We screened hundreds of PGPRs from a near 10,000 PGPR culture library at Auburn University against Drosophila melanogaster larvae to identify strains with initial insecticidal activity. Strains which exhibited initial toxicity toward D. Melanogaster larva were then pushed through a directed evolution pipeline to enhance insecticidal activity. Our study successfully identified PGPRs with insecticidal properties as well as those which were able to be directed towards higher toxicity. Notably, we identified endophyte PGPRs from cotton which possessed insecticidal properties.