A new paper published in PLoS Biology characterizes two bacterial death pathways
Programmed cell death (PCD) in eukaryotes is a well-studied process that is used by organisms to maintain homeostasis. The mechanisms of PCD are under intense study because altered regulation leads to excessive cell death (inflammatory diseases) or excessive cell growth (cancer). The classic pathway in eukaryotes is apoptosis. Likewise, some bacteria also contain PCD pathways, but the reactions are less well characterized. In bacterial PCD, it is also not clear how a death program in single-celled organisms provides an evolutionary advantage. It is important to note that PCD refers to any form of cell death mediated by an intracellular program, regardless of whether the program displays all of the hallmarks of eukaryotic apoptosis.
In bacteria, PCD is mediated through modules that consist of a pair of genes, called “addiction modules” or toxin-antitoxin (TA) systems. One gene of the module encodes for a toxin, and the second gene encodes for a labile antitoxin. Under normal growth conditions (that is, non-stressed), the continual production of the antitoxin inhibits the activity of the toxin.