| Abstract: | Esterases of 53 strains of Yersinia enterocolitica sensu stricto, including five previously defined biotypes, and 30 strains of Yersinia pseudotuberculosis were analysed by horizontal polyacrylamide-agarose gel electrophoresis and by isoelectrofocusing in thin-layer polyacrylamide gel. Esterase bands were defined by their range of activity towards several synthetic substrates, their resistance to heat and to di-isopropyl fluorophosphate. The two species were characterized by distinct electrophoretic patterns of their esterases. The apparent molecular weights of the heat-resistant esterase of Y. enterocolitica and of the major heat-resistant esterase of Y. pseudotuberculosis, as determined by polyacrylamide gradient gel electrophoresis, were estimated to be 52 000 and 250 000, respectively. On the basis of electrophoretic mobilities and isoelectric points of esterases produced by strains of Y. enterocolitica, five principal zymotypes were observed: two for strains of biotype 1, two for strains of biotypes 2 and 3, respectively, and only one for strains of both biotypes 4 and 5. The zymotypes of strains of biotypes 2, 3, 4 and 5 appeared to be more closely related to one another than to zymotypes of strains of biotype 1. Variations in number or mobility of bands observed within each biotype of Y. enterocolitica and within some serotypes of Y. pseudotuberculosis could represent an additional marker for epidemiological analysis. |
