Properties of Escherichia coli Mutants Deficient in Enzymes of Glycolysis

Abstract

Physiological properties of E. coli mutants defective in glyceraldehyde 3-phosphate dehydrogenase, glycerate 3-phosphate kinase or enolase are described. Introduction of a lesion in any one of the reversible steps catalyzed by these enzymes impaired glycolytic and gluconeogenic capabilities of the cell and generated an obligatory requirement for a source of C above the block (gluconeogenic) and one below (oxidative). A mixture of glycerol and succinate supported the growth of these mutants. Mutants lacking glyceraldehyde 3-phosphate dehydrogenase and glycerate 3-phosphate kinase could also grow on glycerol and glyceric acid, and enolase mutants could grow on glycerate and succinate, but double mutants lacking the kinase and enolase required L-serine in addition to glycerol and succinate. Titration of cell yield with limiting amounts of glycerol with Casamino acids in excess, or vice versa, showed the gluconeogenic requirement of a growing culture of E. coli to be 1/20 of its total catabolic and anabolic needs. Sugars and their derivatives inhibited growth of these mutants on otherwise permissive media. The mutants accumulated glycolytic intermediates above the blocked enzyme on addition of glucose or glycerol to resting cultures. Glucose inhibited growth and induced lysis. These effects could be substantially overcome by increasing the osmotic strength of the growth medium and by including 5 mM cyclic AMP therein. This substance countered to a large extent the severe repression of .beta.-galactosidase synthesis that glucose caused in these mutants.