Lactate and malate dehydrogenase activities of non-pathogenic strains of Escherichia coli

Thirteen cultures of Escherichia coli, seven non-enteropathogenic and six enteropathogenic, were compared on the basis of D-lactate and L-malate dehydrogenase activities. Spectrophotometric and starch-gel electro-phoretic methods were employed. Spectrophotometric studies showed differences in both D-lactate and L-malate dehydrogenase activities among the thirteen individual Escherichia coli strains but no definite difference was found between the non-enteropathogenic and enteropathogenic groups on the basis of the two enzyme systems. Starch-gel electrophoretic studies indicated only a single band for both D-lactate and L-malate dehydrogenase enzymes in all thirteen Escherichia coli strains with no noted difference in the electrophoretic mobility between non-enteropathogenic and enteropathogenic groups. All of the L-malate dehydrogenase bands migrated 0.5 cm further than did the bands of D-lactate dehydrogenase. No marked difference was found between the non-enteropathogenic and enteropathogenic strains of Escherichia coli on the basis of their D-lactate and L-malate dehydrogenase enzymes.