title: Toxin on a stick: modular CDI toxin delivery systems play roles in bacterial competition.
abstract: Contact-dependent growth inhibition (CDI) is the first contact-dependent competition system identified in bacteria. CDI is mediated by the CdiA/CdiB two-partner secretion system, and the BamA outer membrane protein serves as the CDI receptor on target cells. A small immunity protein, CdiI, is required to protect inhibitor cells from their own CDI system. Recent results from our group show that CDI systems are present in a number of important gram-negative plant and animal pathogens. The C-terminal region of CdiA (CdiA-CT) is polymorphic and contains growth inhibitory activity. The CdiA-CT from uropathogenic Esherichia coli 536 is a tRNase whereas a CdiA-CT from Dickeya dadantii 3937 has DNase activity. Accordingly, these bacteria contain distinct CdiI proteins, which specifically bind and inactivate cognate CdiA-CT. Remarkably, CdiA-CTs are modular: one CdiA "stick" can deliver different CdiA-CT toxins. We discuss these findings as well as results showing that CDI plays an important role in intra-strain bacterial competition in the natural world. A detailed mechanistic understanding of CDI could facilitate development of probiotics and antimicrobials that target specific pathogens.
authors.affiliation: Molecular Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Aoki
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Poole
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Hayes
authors.forename: David A
authors.initials: DA
authors.lastname: Low
mesh_terms: D000595:Amino Acid Sequence; D018407:Bacterial Physiological Phenomena; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D016415:Sequence Alignment
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins