Lipopolysaccharide (LPS) was purified from 40 isolates of Edwardsiella ictaluri by two methods: (1) enzyme digestion and hot aqueous phenol extraction and (2) enzyme digestion and gel exclusion chromatography. Purified LPS was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and by immunoblot analysis. Both methods of purification yielded smooth LPS as evidenced by a ladderlike pattern of more than 40 LPS bands. With silver staining, both low-and high-molecular-mass LPS bands were seen. Lower-molecularmass LPS stained more intensely than higher-molecular-mass LPS bands, indicating a preponderance of lower-molecular-mass LPSs. Lipopolysaccharide bands from the 40 isolates migrated similarly within SDS-PAGE gels, indicating a high degree of structural similarity among the isolates examined. The ladderlike array was more easily seen with immunoblot analysis than with silver staining of SDS-PAGE gels. Additionally, immunoblot analysis revealed a high degree of antigenic similarity among the 40 isolates.

Flagella were isolated and purified by acid dissociation and by cell solubilization from 10 isolates of Edwardsiella ictaluri derived from channel catfish Ictalurus punctatus. The preparations were examined ultrastructurally and electrophoretically. Ultrastnicturally, flagella isolated by the two methods were morphologically different. Flagellar filaments purified by acid dissociation were of various lengths, and hooks and basal bodies were not seen. When cell solubilization was used, flagellar filaments were more uniform in length, and hooks and basal bodies were evident. A flagellar sheath was not seen in either preparation. Electrophoretic (SDS-PAGE) analysis of flagella isolated by either method showed two proteins with apparent molecular masses of 42 and 38 kilodaltons in gels stained with Coomassie Brilliant Blue.