6533b86ffe1ef96bd12cdf5c

RESEARCH PRODUCT

Functional citric acid cycle in an arcA mutant of Escherichia coli during growth with nitrate under anoxic conditions

Dorina VladCorinna ProhlBirgit WackwitzGottfried Unden

subject

GlycerolCitric Acid CycleDehydrogenasePseudomonas fluorescensPseudomonas fluorescensBiochemistryMicrobiologychemistry.chemical_compoundPseudomonasGenes RegulatorEscherichia coliGeneticsGlycerolAnaerobiosisMolecular BiologyDerepressionNitratesbiologySuccinate dehydrogenaseGeneral MedicineMetabolismbiology.organism_classificationPseudomonas stutzeriCitric acid cycleGlucoseBiochemistrychemistryGenes BacterialMutationbiology.proteinOxidation-Reduction

description

The operation of the citric acid cycle of Escherichia coli during nitrate respiration (anoxic conditions) was studied by measuring end products and enzyme activities. Excretion of products other than CO2, such as acetate or ethanol, was taken as an indication for a non-functional cycle. From glycerol, approximately 0.3 mol acetate was produced; the residual portion was completely oxidized, indicating the presence of a partially active citric acid cycle. In an arcA mutant devoid of the transcriptional regulator ArcA, glycerol was completely oxidized with nitrate as an electron acceptor, demonstrating derepression and function of the complete pathway. Glucose, on the other hand, was excreted mostly as acetate by the wild-type and by the arcA mutant. During growth on glucose, but not on glycerol, activities of succinate dehydrogenase and of 2-oxoglutarate dehydrogenase were missing nearly completely. Thus, the previously described strong repression of the citric acid cycle during nitrate respiration occurs only during growth on glucose and is the effect of anaerobic and, more important, of glucose repression. In Pseudomonas fluorescens (but not Pseudomonas stutzeri), a similar decrease of citric acid cycle function during anaerobic growth with nitrate was found, indicating a broad distribution of this regulatory principle.

https://doi.org/10.1007/s002030050608