Cell surface of the fish pathogenic bacterium Aeromonas salmonicida. II. Purification and characterization of a major cell envelope protein related to autoagglutination, adhesion and virulence.

The purification of the major protein of the membrane fraction of an autoagglutinating strain of Aeromonas salmonicida is described. This protein, designated as additional cell envelope protein, is water-insoluble, has a molecular weight of about 54 000 and its amino terminal sequence is H2N-Asp-Val-Leu-Leu. Neither sulphur-containing amino acids nor sugar residues were detected. Its amino acid composition, which shows that the additional cell envelope protein is hydrophobic in nature, is remarkably similar to those of various proteins known to be present in additional surface layers of other bacteria, to the adhesive K88 fimbriae of enteropathogenic Escherichia coli and to a pore protein of the outer membrane of E. coli K12.