coli to infect and colonize the mammalian host. this website We are gratefully indebted to Juan Anguita, Associate Professor at Amherst Veterinary and Animal Sciences, for suggested improvements to the manuscript. N.N. was a recipient of fellowships from the University of Leon. This work was supported by grants from the Direccion General de Investigación (AGL2007-62428) and Junta de Castilla y León (JCyL 32A08). “
“The type IV secretion system (T4SS) contributes to Brucella intracellular survival through its effector proteins. Comparative proteomic analysis showed that intracellular survival proteins are expressed

differentially in a virB mutant. Interestingly, several outer membrane proteins (OMPs) are also differentially expressed, implying that T4SS might Navitoclax price affect the OM properties of Brucella. To further evaluate the impact of T4SS on OM, in the present study, the OM proteomes were isolated and compared. Many more products of OMPs, particularly different products of the Omp25/Omp31 family, were found to be altered in the virB mutant. The transcription profiles of Omp25/Omp31 were different from those of their protein products, implying their regulation by virB at both transcriptional and post-transcriptional levels. The virB mutant aggregates at a high cell density and produces exopolysaccharide,

a phenotype resembling that of the vjbR mutant. The virB mutant showed increased sensitivity to polymyxin B and decreased survival under oxidative, high-salt and high-osmolarity stresses, indicating drastic membrane alterations. These results indicated that in addition to being an effector protein secretion system, T4SS affects OM properties that might be important for the adaptation of Brucella to both Carnitine dehydrogenase in vitro and in vivo hostile environments. Brucellosis, also called Malta fever, is a zoonotic disease caused by members of the genus Brucella. Brucella

are remarkably well adapted to the intracellular lifestyle, being able to survive and replicate inside host cells by creating a membrane-bound compartment (Pizarro-Cerda et al., 1998; Ficht, 2003). This is one of the bases for the still poorly understood chronicity of Brucellosis. In an attempt to unravel Brucella virulence factors by transposon mutagenesis, a type IV secretion system (T4SS) encoded by the virB operon was identified (O’Callaghan et al., 1999). The Brucella virB mutants lost the ability to affect the endosomal pathway to dock with the endoplasmic reticulum (ER) and were unable to survive within macrophages and mice (Sieira et al., 2000; Watarai et al., 2002). As a secretion system, T4SS may contribute to Brucella intracellular survival through its effector proteins. A recent report showed that two proteins, VceC and VceA, were translocated into host cells by T4SS.