Partial purification and properties of a haemolytic activity (T-lysin) from Aeromonas salmonicida (original) (raw)
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Biochimica et Biophysica Acta (BBA) - Biomembranes, 1985
The identification of lipopolysaccharide as periodic acid-Schiff positive material, present in the membrane fraction of the fish pathogenic Gram-negative bacterium Aeromonas salmonicida, analyzed by SDS-polyacrylamide gel electrophoresis, is shown. Such analysis has revealed several periodic acid-Schiff positive bands and many membrane proteins among which a pathogenicity-related M r 54 000 protein as a constituent of an additional surface layer outside the outer membrane (Evenberg et al., (1982) Biochim. Biophys. Acta 684, 241-248). The latter protein, designated as additional cell envelope protein or ACE protein, has been purified and characterized in our laboratory (Evenberg and Lugtenberg, (1982) Biochim. Biophys. Acta 684, 249-254). (2) Most strains produce both high and low molecular weight lipopolysaccharide species, presumably corresponding with the presence and (virtual) absence, respectively, of an O-antigenic chain. The property to produce high molecular weight lipopolysaccharide can be lost upon subculturing in laboratory growth media and such is greatly enhanced by the prior loss of the ability to produce ACE protein. (3) Lipopolysaccharide and ACE protein were identified as the major antigens. A new polysaccharide-like antigen, designated as PS-antigen, was detected. Moreover, immunological indications for the presence of a lipoprotein in A. salmonicida are described. (4) The surface localization of the antigens was determined by testing whether preadsorption of antisera by intact cells decreased the binding of IgG to these antigens, or decreased the ability of the sera to agglutinate cells. According to these criteria lipopolysaccharide, ACE protein and PS-antigen are the major surface-located antigens. (5) Material cross-reactive with lipopolysaccharide, ACE protein and PS-antigen has been found in a large number of strains. (6) Several lines of evidence indicate the presence of interactions between ACE protein and lipopolysaccharide. (7) Based on these results a molecular model of the cell envelope of virulent A. salmonicida is presented.
Novel antigens expressed by Aeromonas salmonicida grown in vivo
Infection and Immunity, 1993
Virulent and avirulent Aeromonas salmonicida strains grown inside intraperitoneal implants in Rainbow trout (Oncorhynchus mykiss) were examined for unique antigen expression. Western blots (immunoblots), performed with immune rabbit serum raised against in vivo-grown cells, revealed several unique antigens. With the exception of lipopolysaccharide (LPS), these novel antigens were destroyed after proteinase K treatment. The majority of these antigens were not induced in vitro in response to either iron limitation or anaerobiosis. In addition, electron microscopy demonstrated the presence of a putative capsule on in vivo-grown cells. Purification and fractionation of this carbohydrate material from cells grown in carbon-rich synthetic media resulted in the isolation and separation of an antigenically distinct LPS not seen with cells grown in standard media. Antiserum raised against in vivo-grown cells recognized both this LPS and the typical LPS of A. salmonicida apparent in in vitro-...
Journal of Fish Diseases, 1994
A collection of 130 strains of the bacterial fish pathogen Aeromonas salmonicida subsp. salmonicida isolated from diseased salmonids in Denmark, Norway, North America and Scotland has been characterized with regard to protein patterns, antibiotic resistance and exoprotease activity. Whole eell and outer membrane protein profiling could distinguish three different profiles in A. salmonicida. Eight outer membrane proteins were demonstrated (49, 40, 38, 37, 33, 31, 30 and 29kDa). One protein profile was deficient in a 38kDa outer membrane protein and instead contained an outer membrane protein of 37 kDa whieh was not detectable among the other protein profiles. Strains with the 37 kDa outer membrane protein showed multiple low-level antibiotie resistance towards eephalothin, penicillin, chloramphenieol, tetracyeline and quinolones. In addition, these strains were exoprotease deficient. Strains with the 37 kDa protein were unable to degrade cattle and trout serum proteins and displayed a delayed degradation of casein. Haemolysis on cattle blood agar plates was similarly delayed. In vivo examination of extracellular products from a normal protein profile strain and one with the 37 kDa outer membrane protein demonstrated major differenees in pathologieal effeets in rainbow trout. The strain possessing the 37 kDa outer membrane protein produced almost no pathological effects while the normal protein profile strain produced typical furuncles.
Cell surface of the fish pathogenic bacterium Aeromonas salmonicida
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1982
A comparison was made of membrane protein patterns of various Aeromonas salmonicida strains, initially isolated from different habitats with respect to fish species affected, pathological entity, and geographic location of the outbreak of the disease. A major protein with a molecular weight of 54 000 was found in all autoagglutinating strains, whereas this protein is present in low amounts, or not at all, in non-autoagglutinating strains. Evidence for a causal relationship between the presence of this protein and the phenomenon of autogagglutination came from the observation that a change of the growth medium led simultaneously to an almost complete loss of the additional cell envelope protein and the property of autoagglutination. As it has already been reported that autoagglutination is correlated with the presence of an additional cell surface layer, we hypothesize that the additional cell envelope protein is the (major) suhunit of this layer. The application of the gel immuno radio assay, an immunological technique suited to detect antigens in a gel, revealed that the additional cell envelope proteins of all tested strains are immunologically related. The possibility to the use of this protein as a component of a vaccine against A. sMmonicida infections is discussed.
Dormant/unculturable cells of the fish pathogen Aeromonas salmonicida
Microbial Ecology, 1995
Viable cells of Aeromonas salmonicida remained in experimental marine systems after plate counts indicated an absence of culturable cells. These so-called/viable but nonculturable (VBNC) cells were coccoid and smaller than their normal culturable counterparts. There was no reduction in lipopolysaccharide of the VBNC cells. There was an alteration in protein composition, however, with a decline in some (15, 70, 30, 22, and 17 kDa), but an increase in another protein (49 kDa). A significant loss of DNA occurred. The VBNC cells responded to fluorescent antibodies prepared against A. salmonicida by developing enlarged and bizarre shapes in the presence of yeast extract and nalidixic acid (the direct viable count technique), and they demonstrated respiratory activity. It was concluded that A. salmonicida survived in seawater, but major morphological changes occurred with cells retaining some viability but losing pathogenicity to Atlantic salmon (Salmo salar).
Virulence properties and enterotoxin production of Aeromonas strains isolated from fish
Infection and immunity, 1988
The biological activities in vivo and in vitro of 59 motile Aeromonas spp. isolated from fish and water tanks were simultaneously analyzed in poikilothermic and homoiothermic systems. A total of 64.3% of the isolates tested were pathogenic for fish, and 62% of Aeromonas hydrophila and A. sobria isolates either virulent or nonvirulent for fish were enterotoxigenic. Although the majority of the strains were proteolytic and amylolytic and produced DNase, other activities, such as elastase and staphylolysis, were only present in A. hydrophila. Most of the strains (96%) produced hemolysins, and 68% had agglutinating capacity, but neither isolates pathogenic for fish nor enterotoxigenic isolates showed specificity for trout or human erythrocytes, respectively. The production of siderophores, agglutination in acriflavine, and precipitation after boiling were found not to be useful tests for screening virulent strains. Although statistical analysis revealed a significant relationship betwee...
Aquaculture, 1987
In this study we have analysed the biochemical, enzymatic, and cell surface properties of 59 Aeromonas strains isolated from fish culture systems, with the aim of establishing the possible relationships among some of these phenotypic characters and pathogenicity. The cytotoxic activity of extracellular products was also evaluated. Virulence assays showed that 64.3% of the strains were pathogenic for fish. However, both pathogenic and non-pathogenic Aeromonas isolates were able to produce enterotoxins. The majority of the strains were proteolytic, amylolytic and produced DNAase. Nevertheless, elastase and staphylolytic activities were present only in A. hydrophilu. Although 96% of the isolates produced haemolysins, a clear specificity toward trout or human erythrocytes was not found in the pathogenic strains. Similarly there was no specificity in the haemagglutinating activity. Statistical analysis of the association between virulence and phenotypic traits revealed a positive relationship among virulence for fish and arabinose and sucrose fermentation, elastase and haemolysis of human erythrocytes. However, only the LDC test showed a significant relation with enterotoxin production. These findings suggest that different mechanisms are involved in the invasion by Aeromonas of their poikiIotherm and homeotherm hosts. Extracellular products of the Aeromonas strains displayed cytotoxicity on fish cell-lines regardless of the virulence capacities of the strains, which indicates that cytotoxic activity is not an adequate criterion of pathogenicity.
Atypical characteristics of the salmonid pathogen Aeromonas salmonicida
Journal of General Microbiology, 1991
Incubation of Aeromonas sdmonicida at supra-optimal temperatures, i.e. 30-37 "C, resulted in the expression of motility by polar flagella, and changes in sugar fermentation patterns, e.g. loss of acid production from mannitol, loss of the ability to degrade complex molecules (aesculin, DNA, elastin and gelatin), and an increase in antibiotic resistance (notably co-trimoxazole). Motility was enhanced in cultures grown in brain heart infusion broth supplemented with 18% (w/v) Ficoll.