Selection of Escherichia coli mutants lacking glucose-6-phosphate dehydrogenase or gluconate-6-phosphate dehydrogenase.
Glucose is metabolized in Escherichia coli chiefly via the phosphoglucose isomerase reaction; mutants lacking that enzyme grow slowly on glucose by using the hexose monophosphate shunt. When such a strain is further mutated so as to yield strains unable to grow at all on glucose or on glucose-6-phosphate, the secondary strains are found to lack also activity of glucose-6-phosphate dehydrogenase. The double mutants can be transduced back to glucose positivity; one class of transductants has normal phosphoglucose isomerase activity but no glucose-6-phosphate dehydrogenase. An analogous scheme has been used to select mutants lacking gluconate-6-phosphate dehydrogenase. Here the primary mutant lacks gluconate-6-phosphate dehydrase (an enzyme of the Enter-Doudoroff pathway) and grows slowly on gluconate; gluconate-negative mutants are selected from it. These mutants, lacking the nicotinamide dinucleotide phosphate-linked glucose-6-phosphate dehydrogenase or gluconate-6-phosphate dehydrogenase, grow on glucose at rates similar to the wild type. Thus, these enzymes are not essential for glucose metabolism in E. coli.
D004926:Escherichia coli / Q000201:enzymology / Q000378:metabolism*; D005827:Genetics, Microbial; D005942:Gluconates / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D005956:Glucose-6-Phosphate Isomerase / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism*; D008967:Molecular Biology; D009154:Mutation; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism*; D014161:Transduction, Genetic
D005942:Gluconates; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D005956:Glucose-6-Phosphate Isomerase; D005947:Glucose