Outer Membrane Vesicles as a Vehicle for Hydrophobic Quorum Sensing Molecules
Gram-negative bacteria use, among others, hydrophobic signaling molecules for cell-cell communication to coordinate group behavior in a process called quorum sensing. However, due to their hydrophobic character, it is unclear how these molecules are disseminated between bacterial cells. Brameyer et al. (e00740-17) show that the marine bacterium Vibrio harveyi packages CAI-1, an alkyl ketone, into outer membrane vesicles (OMVs). These CAI-1-containing vesicles trigger a quorum sensing phenotype in CAI-1-nonproducing V. harveyi and V. cholerae cells. Packaging of CAI-1 into OMVs not only might stabilize these molecules in an aqueous environment but also might facilitate their distribution over distances.
Biofilms in the Service of Humanity
Liao et al. (e00752-17) describe a novel, self-assembling whole-cell vaccine platform that exploits proteins in the Vibrio cholerae biofilm matrix. When the B subunit of cholera toxin (CTB) is genetically fused to the V. cholerae biofilm matrix protein RbmA, this fusion protein is secreted from the cell and displayed on the cell surface. Sublingual delivery of live, attenuated V. cholerae cells expressing RbmA-CTB elicits a robust and protective mucosal immune response to V. cholerae LPS and CTB. Given its great flexibility, this platform may be expanded to protect against diverse mucosal pathogens.
Vibrio cholerae Outer Membrane Vesicles Inhibit Bacteriophage Infection
Gram-negative outer membrane vesicles (OMVs) serve multiple roles in the biology of bacteria, including a potential general role in defense against phages. Reyes-Robles et al. (e00792-17) support this role by showing that two different strains of Vibrio cholerae—one older and one modern clinical isolate—produce OMVs that inhibit infection by three different virulent phages. Direct binding of phage tail fibers to OMVs was confirmed by cryo-electron microscopy and shown to occur in a receptor-dependent manner using OMVs produced by mutant V. cholerae strains. OMVs as decoys provide yet another strategy in the bacterium-phage arms race.
- Copyright © 2018 American Society for Microbiology.
