title: Type VI secretion delivers bacteriolytic effectors to target cells.
abstract: Peptidoglycan is the major structural constituent of the bacterial cell wall, forming a meshwork outside the cytoplasmic membrane that maintains cell shape and prevents lysis. In Gram-negative bacteria, peptidoglycan is located in the periplasm, where it is protected from exogenous lytic enzymes by the outer membrane. Here we show that the type VI secretion system of Pseudomonas aeruginosa breaches this barrier to deliver two effector proteins, Tse1 and Tse3, to the periplasm of recipient cells. In this compartment, the effectors hydrolyse peptidoglycan, thereby providing a fitness advantage for P. aeruginosa cells in competition with other bacteria. To protect itself from lysis by Tse1 and Tse3, P. aeruginosa uses specific periplasmically localized immunity proteins. The requirement for these immunity proteins depends on intercellular self-intoxication through an active type VI secretion system, indicating a mechanism for export whereby effectors do not access donor cell periplasm in transit.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Alistair B
authors.initials: AB
authors.lastname: Russell
authors.forename: Rachel D
authors.initials: RD
authors.lastname: Hood
authors.forename: Nhat Khai
authors.initials: NK
authors.lastname: Bui
authors.forename: Michele
authors.initials: M
authors.lastname: LeRoux
authors.forename: Waldemar
authors.initials: W
authors.lastname: Vollmer
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Mougous
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000378:metabolism; D001433:Bacteriolysis; D006090:Gram-Negative Bacteria / Q000166:cytology* / Q000378:metabolism*; D006868:Hydrolysis; D056265:Microbial Interactions; D009113:Muramidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010457:Peptidoglycan / Q000378:metabolism; D019897:Periplasm / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D016958:Pseudomonas putida / Q000254:growth & development / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D001427:Bacterial Toxins; D010457:Peptidoglycan; D009113:Muramidase; D000581:Amidohydrolases; C019665:amidase