To determine whether
enzyme electrophoretic polymorphism in Escherichia coli populations was influenced by environmental background, the mobilities of four electrophoretically variable
esterases (A, B, C and I) were examined. The distinction between isolates was established by significant differences in the electrophoretic distribution and the genetic diversity coefficient of individual
esterases. Principal components analysis on each population and on all strains revealed three groups of
allozymes. The first, characterized by slow electrophoretic mobilities of
esterase B, was frequently observed in strains obtained from human extra-intestinal
infections and rarely in commensal organisms. The second, characterized by fast mobilities of
esterases A and B, was frequently found in animal isolates. The third, characterized by prominence of the most common mobilities of
esterases B and A, was recovered in all populations. These results were confirmed by discriminant analysis. Among the 610 strains investigated, 316 electrophoretic types (distinctive combinations of
allozymes of the four varieties of
esterases) were distinguished, illustrating high
esterase polymorphism.