Computerized comparison of the protein compositions of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum strains

Protein profiles of six Erysipelothrix rhusiopathiae strains, five Erysipel othrix tonsillarum strains and three Erysipelothrix strains of uncertain ta xonomic position were studied by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). In a computerized comparison of the protein pa tterns of the strains, the level of similarity between the strains was dete rmined. The SDS-PAGE protein bands were divided into 14 groups based on mol ecular weight. The relative distribution of proteins within these groups wa s used to characterize the strains. These distribution patterns were analys ed by computing Pearson's correlation coefficient between strains, and by c luster analysis based on Euclidean distances and the unweighted pair-group method of arithmetic averages (UPGMA). The geometric mean of the similariti es calculated by Pearson's correlation coefficient was 0.980 +/- 0.018 betw een the E. rhusiopathiae strains and 0.979 +/- 0.013 for E. tonsillarum str ains. The value was 0.932 +/- 0.036 between the strains belonging to differ ent species. However, a threshold Value applicable for identification of a given strain to a species could not be established. Of the three strains of uncertain taxonomic position, the strains designated Rotzunge and Iszap 4 had a protein composition more similar to that of E. tonsillarum than to th at of the E. rhusiopathiae type strain. The strain designated Pecs 56, whic h may be a member of a new species according to literature data, gave incon sistent results Ly the two methods used. The computerized evaluation method developed here is suitable for the comparison of the protein composition o f the strains and for thr construction of the protein similarity tree by cl uster analysis.