Virulence of Vibrio anguillarum with Particular Emphasis on the Outer Membrane Components

Abstract

The plasmidless Vibrio anguillarum strain PT479 obtained after seven passages in ayu Plecoglossus altivelis was highly virulent to ayu. An isogenic strain from the 20th passage in a lab medium had low virulence. The uptake of radioactive iron by the high-virulent strain was more rapid than that of the low-virulent strain. The highly virulent strain was able to grow in an M9 salts medium supplemented with 0.5% (wt/vol) glucose, 20μg each of aspartic acid and histidine per ml, and 2μM transferrin. The low-virulent strain was inhibited under such conditions. The outer membrane protein pattern did not change in either the high-virulent strain or the low-virulent isogenic strain. However, there was a difference in lipopolysaccharide (LPS) structure. A high-molecular weight band was evident in the high-virulent strain. The amount of proteins with the molecular weights ranging from 67, 000 to 100, 000 daltons increased in the outer membrane of both high-and low-virulent strains grown under iron limitation. The production of LPS was enhanced in the high-virulent strain compared to the low-virulent strain as determined by the Limulus test.