Peptide Rings Death Knell for Bacteria

Programmed cell death is best known in eukaryotic, multicellular organisms, but it also occurs in bacteria. In both cases, sacrifice of some cells can enable the rest to survive. Molecular biologist Hanna Engelberg-Kulka of Hebrew University's Hadassah Medical School, in Jerusalem, and colleagues have now found that programmed cell death in Escherichia coli bacteria depends on cell-to-cell communication, a process known as quorum sensing. They also found that the death process requires that a certain minimum number of bacteria be present (Science 2007, 318, 652). The communicating cells produce and emit an "extracellular death factor." Once this signaling molecule reaches a sufficient concentration, it activates the cell-death pathway in a subset of the cells. The researchers have isolated and characterized the death factor, which is a pentapeptide. They note that the compound is the first peptide reported to be involved in quorum sensing in E. coli. The findings could provide a lead for developing new antibiotics.