Bacteria use a variety of methods to combat predators and competitors in their natural environments. Bacteria are vulnerable to predator grazing, and can produce and secrete chemicals to deter predation. Nematodes are a major bacterial predator in nature, particularly rhabditid nematodes like C. elegans that reproduce in large numbers very quickly when they come upon an abundant food source. Violacein is a secondary metabolite that is secreted by various genera of soil and water bacteria. It is a bis-indole derivative that is easy to visualize due to its distinct purple color. Violacein has garnered interest due to its many therapeutic effects such as antimicrobial, anti-protozoal and anti-cancer properties, but its mechanism of action in these effects is not clear. We show that violacein is effective in preventing bacterial grazing by C. elegans. Violacein exposure results in decreased consumption of bacteria and avoidance of violacein-producing OP50, and this may account for the decreased bacterial grazing. To elucidate the mechanism in which violacein acts on C. elegans, we observed worms cultured in the presence of violacein. We found that worms cultured with either purified violacein or violacein-expressing OP50 showed slower development and decreased fecundity. In closer observation we saw several phenotypes including an expansion of the intestinal lumen, a decrease in intestinal volume, and retention of late-stage eggs in the gonad. In addition we were able to observe accumulation of purified deoxyviolacein, a precursor of violacein, in vesicles in the intestine. To identify the effect that violacein may have on intestinal cells, we used the autophagosome marker
lgg-1::GFP and noticed increased autophagy in intestinal cells. Currently, we are testing various candidate mutants and various GFP indicator strains to further elucidate the molecular target of violacein.