User:Missonic/Sandbox

=Type VI Secretion System=

The Type VI secretion system (T6SS) is a bacterial export system that transports proteins from the bacterial cytosol towards host cells. So far, two different protein families (Hcp and VgrG proteins) have been identified as T6SS substrates. Gene-clusters coding for T6SS usually contain 15-20 different genes.

Type VI secretion systems have been discovered in Gram-negative bacteria in 2006 : Vibrio cholerae, the causative agent of cholera, was shown to escape Dictyostelium discoideum by using a T6SS. The related genes were assigned as vas-genes (virulence-associated secretion). T6SS are present in many different Gram-negative pathogens or symbionts. The T6SS best characterized are from Vibrio cholerae, Burkholderia mallei, Edwardsiella, Francisella tularensis, Pseudomonas aeruginosa, Salmonella enterica and Rhizobium leguminosarum. It is mostly associated with virulence in mammalian cells or against other bacteria (ref). Vibrio cholerae is also toxic to mammalian J774 macrophages based on T6SS activity (ref). A role in symbiontic interactions has been described for Rhizobium, where the T6SS functions in nodule formation. Hcp1, a protein secreted by Pseudomonas aeruginosa T6SS, has been found in cystic fibrosis patients sputum. In addition, serum antibodies from patients directed against Hcp1 have been identified.