Esterase electrophoretic pattern relatedness between Shigella species and Escherichia coli

Esterases of 57 strains of Shigella dysenteriae, Sh. flexneri, Sh. boydii and Sh. sonnei and 26 strains of Escherichia coli, including the Alkalescens Dispar group, were compared by polyacrylamide-agarose gel electrophoresis. Six types of esterase bands differing in their ability to hydrolyse synthetic substrates and in their sensitivity to heat and to di-isofluoropropyl phosphate were defined. Individual activities and sensitivities of these bands and the apparent molecular weight of the major esterase, estimated to be 58000 by polyacrylamide gradient gel electrophoresis, were identical for both Shigella species and E. coli. One esterase with a molecular weight of 104000 was found in some strains of E. coli. Variations in the number and mobility of bands among Shigella strains defined different esterase patterns (zymotypes) which appeared to be distinct for each species.