Yeast is not the simple single-celled microorganism we once thought, but a competitive killer. When starved of glucose, yeast releases a toxin that will poison other microorganisms that have entered its surrounding habitat, even its own clones. This venomous phenomenon was previously unknown and contributes to our understanding of unicellular microorganism behavior, the evolution of unicellular to multicellular organisms, as well as having potentially useful applications for the food industry.