Toxins on Sticks
A study published in the November 18th issue of the journal Nature shows that bacteria express stick-like contact-dependent inhibitor (CDI) proteins on their cell surface that contain an embedded toxin at the tip. The toxin is delivered to neighboring cells upon direct cell contact. The work is the result of collaboration between the laboratories of Christopher Hayes, David Low, Peggy Cotter and Stephen Poole in MCDB. Stephanie Aoki, lead author, with help from Bruce Braaten and Julia Webb, showed that toxic tips are interchangeable; a toxic tip from the plague bacillus inhibited growth of E. coli target cells after melding onto the CDI stick of uropathogenic E. coli. Elie Diner, second author, showed that toxic tips have different activities expected to block protein synthesis including breakage of transfer RNA and ribosomal RNA. Together, Elie and Stephanie showed that each toxin system also expresses an immunity protein that binds to and inactivates its own toxin. Claire t'Kint de Roodenbeke showed that the pathogen Dickeya dadantii uses a CDI system for growth competition on plants. Stephen Poole's analysis indicates that CDI systems are widespread amongst many important bacterial pathogens.