[New data on the specificity and genetic control of the capsular antigen (F1) in Yersinia pestis].

The specific features of the synthesis of antigenic fractions F1, obtained from the strains of different species of enterobacteria and their hybrids inheriting Y. pestis plasmid pYT, were determined at different cultivation temperatures and the preparations of these antigenic fractions were characterized. Preparations containing the diagnostic antigenic determinant F1 were obtained from disintegrated bacteria of Y. pestis plasmid-free strain and microbial cells of Klebsiella pneumoniae, Citrobacter freundii and Escherichia coli initial recipient cultures by Baker's method. These data were indicative of the chromosomal control of the synthesis of antigen F1, responsible for the manifestation of protective activity. The antigen synthesized in the absence of pYT was practically, not secreted on the cell-wall surface and could not be determined by tests made with the use of whole bacterial cells. The antigen thus detected did not possess the properties of the preparation of antigen F1, obtained from Y. pestis pYT-containing strain, though it was capable of inducing the formation of F1-specific antibodies.