Release of outer membrane vesicles by Gram-negative bacteria is a novel envelope stress response.
Conditions that impair protein folding in the Gram-negative bacterial envelope cause stress. The destabilizing effects of stress in this compartment are recognized and countered by a number of signal transduction mechanisms. Data presented here reveal another facet of the complex bacterial stress response, release of outer membrane vesicles. Native vesicles are composed of outer membrane and periplasmic material, and they are released from the bacterial surface without loss of membrane integrity. Here we demonstrate that the quantity of vesicle release correlates directly with the level of protein accumulation in the cell envelope. Accumulation of material occurs under stress, and is exacerbated upon impairment of the normal housekeeping and stress-responsive mechanisms of the cell. Mutations that cause increased vesiculation enhance bacterial survival upon challenge with stressing agents or accumulation of toxic misfolded proteins. Preferential packaging of a misfolded protein mimic into vesicles for removal indicates that the vesiculation process can act to selectively eliminate unwanted material. Our results demonstrate that production of bacterial outer membrane vesicles is a fully independent, general envelope stress response. In addition to identifying a novel mechanism for alleviating stress, this work provides physiological relevance for vesicle production as a protective mechanism.
McBroom
Amanda J
AJ
Duke University Medical Center, Department of Biochemistry Box 3711, Durham, NC 27710, USA.
Kuehn
Meta J
MJ
D000222:Adaptation, Physiological; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D004251:DNA Transposable Elements; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D029968:Escherichia coli Proteins / Q000032:analysis / Q000235:genetics; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D050296:Microbial Viability; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D016254:Mutagenesis, Insertional; D011112:Polymyxin B / Q000494:pharmacology; D021381:Protein Transport
D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D011112:Polymyxin B