SummaryIn Gram-negative bacteria, all components of the outer membrane are synthesized in the cytoplasm or the cytoplasmic leaflet of the inner membrane and must thus traverse the inner membrane and the periplasm on the way to their final destination. In this study, we show Imp/OstA to have characteristics typical for proteins involved in envelope biogenesis. Imp is essential and forms a high-molecular-weight disulphide-bonded complex in the outer membrane. Upon depletion of Imp, lipids and outer membrane proteins appear in a novel membrane fraction with higher density than the outer membrane. We propose Imp to be part of a targeting/usher system for components of the outer membrane.

Interventional PFO closure with the PFO-Star device appears to be a reliable and promising technique resulting in a low recurrence rate of thromboembolic events, especially stroke in patients with a history of cryptogenic ischemia presumably due to paradoxical embolization. To our knowledge, this is the largest coherent and prospective study for interventional PFO closure.

Glycoengineering technology, whereby polysaccharide and protein antigens are enzymatically linked in a simple E. coli production system, has broad applicability for use in vaccine development against encapsulated microbial pathogens.

Growth failure is a classical sign of essential fatty acid deficiency. We investigated whether birth weight correlates with the postnatal essential fatty acid status in a group of 29 premature infants. A significant and positive correlation between body weight and plasma triglyceride content of arachidonic acid (20:4n-6) (r = 0.47, p = 0.01) and total ω-6 long-chain polyunsaturated fatty acids (r = 0.49, p < 0.01) was found. In contrast, there was no positive relation to linoleic acid (18:2n-6) or any ω-3 fatty acid but a significant inverse correlation to α-linolenic acid (18:3n-3). We propose that during early life arachidonic acid may have a growth-promoting effect which could be related to its role as an eicosanoid precursor or to its structural function in membrane lipids.

Type III secretion genes in Aeromonas salmonicida subsp. salmonicida are located on a large plasmid of approximately 140 kb. Cultivation of this organism at elevated temperatures such as 25°C can, however, result in loss of this plasmid. This is accompanied by a loss of virulence for cultured fish cells.

Interventional PFO closure appears to be safe and a promising technique in symptomatic PFO patients with a low incidence of periinterventional complications and recurrent thromboembolic events using three different devices (PFO-Star, Amplatzer PFO occluder or the CardioSeal/Starflex).

An ADP-ribosylating toxin named Aeromonas salmonicida exoenzyme T (AexT) in A. salmonicida subsp. salmonicida, the etiological agent of furunculosis in fish, was characterized. Gene aexT, encoding toxin AexT, was cloned and characterized by sequence analysis. AexT shows significant sequence similarity to the ExoS and ExoT exotoxins of Pseudomonas aeruginosa and to the YopE cytotoxin of different Yersinia species. The aexT gene was detected in all of the 12 A. salmonicida subsp. salmonicida strains tested but was absent from all other Aeromonas species. Recombinant AexT produced in Escherichia coli possesses enzymatic ADP-ribosyltransferase activity. Monospecific polyclonal antibodies directed against purified recombinant AexT detected the toxin produced by A. salmonicida subsp. salmonicida and cross-reacted with ExoS and ExoT of P. aeruginosa. AexT toxin could be detected in a wild type (wt) strain of A. salmonicida subsp. salmonicida freshly isolated from a fish with furunculosis; however, its expression required contact with RTG-2 rainbow trout gonad cells. Under these conditions, the AexT protein was found to be intracellular or tightly cell associated. No AexT was found when A. salmonicida subsp. salmonicida was incubated in cell culture medium in the absence of RTG-2 cells. Upon infection with wt A. salmonicida subsp. salmonicida, the fish gonad RTG-2 cells rapidly underwent significant morphological changes. These changes were demonstrated to constitute cell rounding, which accompanied induction of production of AexT and which led to cell lysis after extended incubation. An aexT mutant which was constructed from the wt strain with an insertionally inactivated aexT gene by allelic exchange had no toxic effect on RTG-2 cells and was devoid of AexT production. Hence AexT is directly involved in the toxicity of A. salmonicida subsp. salmonicida for RTG-2 fish cells.Aeromonas salmonicida subsp. salmonicida is the etiological agent of furunculosis of Salmonidae. This fish disease causes most severe losses in production farms of salmon and trout and leads to the use of large amounts of antibiotics in closed and open waters for prevention and therapy of furunculosis. To develop efficient strategies to prevent outbreaks of A. salmonicida subsp. salmonicida, it is essential to know the main mechanisms of pathogenicity of this pathogen. Several potential virulence factors of A. salmonicida subsp. salmonicida have been described thus far. They include the surface array layer protein (7); hemolysins ASH1, ASH3, and ASH4 (12); H-lysin (29); salmolysin (19); serine protease AspA (32); and the glycerophospholipid:cholesterol acyltransferase (GCAT) complexed with lipopolysaccharide (18). Recent reports demonstrate the role of the S layer in adhesion (11) of A. salmonicida subsp. salmonicida. The other potential virulence factors of A. salmonicida subsp. salmonicida that are currently known do not seem to play a primary role in pathogenesis. GCAT and aspA gene deletion mutants showed that neither GCAT nor aspA is essential ...

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