Inside knowledge of the enemy's weaknesses can help yeast to kill their enemy—other yeast cells—report Reiter et al. on page 353. They show that yeast activate the self-destruct mechanism in their yeast foes.
Self-destruction, or apoptosis, is thought to be a common outcome in yeast cells exposed to environmental stresses, such as peroxide or UV light, or internal stresses, such as aging. Suicide of a unicellular organism is thought to benefit the healthier, surviving members of the population by conserving limited nutrients.
But some members of the yeast populace are far less altruistic—they harbor toxin-producing viral sequences that eliminate other yeast in two ways. At high concentrations, the toxins bring about necrotic death in other cells via several strategies: some make holes in the plasma membrane; others inhibit DNA synthesis. In natural environments, however, the toxins rarely accumulate to such high levels.
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