Photo by Iluisanunez.

This week at the collaborative science blog Nothing in Biology Makes Sense!, contributor Devin Drown discusses a new study of bacterium-on-bacterium violence:

The bacteria produce chemical weapons, bateriocins, which can broadly harm other isolates, but relatives are left unharmed. These chemical weapons can be classified as spiteful: in the process of harming others they also harm the focal individual. This self-harm comes from the cost of making the chemical weapon. Others have labeled this antagonistic trait a greenbeard gene.

To learn what a bacterial chemical weapon has to do with what might otherwise sound like an overenthusiastic celebration of Saint Patrick’s Day—and how both might explain the diversity of living populations, read the whole thing. ◼