[Purification and physico-chemical analysis of the fimbrial antigen in two different genera of Enterobacteriacea: Salmonella enteritidis and Yersinia enterocolitica (author's transl)].

Chemical, physical and immunological properties of the fimbrial antigen of two different genera of Enterobacteriaceae, namely Salmonella (S. enteritidis) and Yersinia (Y. enterocolitica) were analysed. Only a few strains of these two bacterial genera possess a fimbrial antigen which proved to be identical in all tests. Purified fimbriae are unstable in buffer solutions. They tend to form aggregates, patterns of which are between 240000 and 270000. Submitted to solubility testing by various methods these aggregates easily dissociate into particles of different molecular size. Treatment with 1% sodium dodecyl sulphate (SDS) in 1% mercaptoaethanol at 37 degrees C for 60 minutes gave constant reproducible results. The fimbrial protein prepared by this method proved to be an antigenically active unit with a molecular weight of 23450 for S. enteritidis and 23350 for Y. enterocolitica. The electron microscope revealed that purified fimbriae of these two genera consist of extremely thin filaments (1.5 to 2.7 nm), covering the bacterial cell as an envelope. They are supposed to be composed of no more than 2 to 3 peptid chains. The presence of the amino acids tyrosine, phenylalanine and tryptophane may be responsible of the particular behaviour of the fimbriae which according to different external conditions react with different states of dissociation. Probably the filaments are not stable in a solution as single filaments but tend to form oligomer, secondary and tertiary structures. Experiments of isoelectric focusing revealed that both antigens consist of a pure protein component (composed of 17 amino acids) which appears at pH 3.9.