THE ELECTROPHORETIC POLYMORPHISM OF BACTERIAL ESTERASES

The specific activities of esterases and certain other molecular prope rties including immunospecificity indicate that the electrophoretic va riations of these enzymes in bacterial populations are the result of a llelic variations at specific gene loci. The esterase polymorphism of Enterobacteriaceae and some other species isolated from man or animals demonstrates that esterases can distinguish between bacteria at the s pecies or subspecies level, both by their biochemical properties and b y their electrophoretic differences. The esterase data complement DNA hybridization studies and agree with ribosomal DNA polymorphism, espec ially for delineating a phylogenetically distinct group of highly path ogenic strains in Escherichia coli. A two-dimensional electrophoretic profile obtained by establishing a direct correspondence between homol ogous esterase bands resolved by independent runs of isoelectric focus ing and standard electrophoresis considerably improves the detection o f allelic variations, whereas protein titration curves (electrophoresi s in pH gradient) can be used to demonstrate the real electrophoretic homogeneity of allozymes or evalue their molecular relationship in ter ms of apparent amino acid substitutions. This overview establishes tha t esterases, by their significant electrophoretic polymorphism, are re liable molecular markers for systematics and epidemiology, and are sui table enzyme systems for studying population genetics and phylogeny.