Background Outer membrane vesicles (OMVs) are released from the outer membrane of many Gram-negative bacteria. the OMVs and the OM. Furthermore a comparison of the OMV proteomes from two different culture media indicated that the culture conditions have an impact on the protein composition. Interestingly the proteins that are common to both culture conditions are mainly involved XR9576 in virulence. Conclusion Outer membrane vesicles released from the OM of Xcc contain membrane- and virulence-associated proteins. Future experiments will prove whether these structures can serve as “vehicles” for the transport of virulence factors into the host membrane. Background The Gram-negative bacterium Xanthomonas campestris pv. campestris (Xcc) is the causal agent of “black rot” disease in crucifers which include a number of plants of economical importance. Xanthomonas campestris can XR9576 be subdivided into different pathovars according to their host range [1 2 Xanthomonads invade compatible host plants via hydathodes stomata or wound openings. The infection process itself is facilitated by high temperatures and humidity which are climatic characteristics of a Rabbit polyclonal to ADCY2. multitude of developing countries in Latin America Africa and Asia where Xanthomonas epidemics account for substantial economical losses . To gather a deeper understanding of how these bacteria cause disease in different plants the genome sequences of four different Xanthomonas pathovars were established [3-5]. Furthermore recent XR9576 sequencing projects have revealed the genomic information of three different Xanthomonas campestris pv. campestris strains [3 6 7 This plethora of genomic information is a useful resource to identify genes involved in host specific pathogenicity and in more general virulence XR9576 mechanisms. The specific host range determining mechanisms are orchestrated by the fine tuned interaction of pathogen derived effector proteins and structures within the host cell [8 9 These proteins are commonly directly delivered into the sponsor cell from the type-III secretion program (TTSS) which can be extremely conserved among Gram-negative pathogens. The the different parts of the TTSS are often encoded from the so-called hrp-operon (hypersensitive response and pathogenicity) which includes around 20 genes which nine are extremely conserved and for that reason termed hrc . The transcription from the hrp-genes can be tightly controlled in support of activated in conditions that resemble the sponsor . Among the crucial proteins from the TTSS may be the HrpF pore which can be inserted in to the host’s plasma membrane and allows the pathogen to route effector proteins in to the sponsor cell [11 12 General virulence systems involve proteins in charge of trace component acquisition (e.g. iron) extracellular protein with lytic features aswell as proteins complexes involved with their secretion [13-15]. These protein help the colonization from the sponsor and a saprophytic life-style in later phases of disease. Just recently the part of external membrane derived vesicles so-called outer membrane vesicles (OMVs) have been studied in detail. They have been found to act as vehicles for the transport of virulence associated compounds into other cells [16-18]. OMVs are known to be constantly liberated from the outer membrane of most Gram-negative bacteria . It has been demonstrated that they contain outer membrane and periplasmic proteins and in some cases DNA or cell-cell signalling molecules [20 21 This makes OMVs an ideal structure to transport hydrophobic compounds like membrane proteins into the host. The best-studied membrane anchored virulence factor is the ClyA protein from enterotoxic bacterium E. coli which forms pores inside the host membrane and thus causes lysis. It has been demonstrated that ClyA is inserted into the outer membrane of the pathogen as inactive monomers which are then released and embedded in OMVs where they are converted into an active form that assembles into the multimeric membrane pore. Upon fusion of the OMV with the host membrane a functional ClyA pore is inserted . This clearly indicates the potential of OMVs to deliver membrane active virulence factors into the host. In this study we present the proteome of OMVs isolated from the culture supernatant of the Xcc strain B100. Furthermore we could demonstrate that the composition of the OMV proteome differs from that of the outer membrane implying some kind of protein sorting mechanism. A.