The transport of Krebs-cycle intermediates in Azotobacter vinelandii under various metabolic conditions

Abstract

1. 1. The oxidation of Krebs-cycle intermediates in Azotobacter vinelandii is inhibited by the uncouplers carbonyl cyanide p- trifluoromethoxyphenylhydrazone and carbonyl cyanide m- chlorophenylhydrazone , and energy-transfer inhibitors such as oligomycin, N,N′- dicyclohexylcarbodiimide or Dio-9. 2. 2. Uncouplers and energy-transfer inhibitors have a synergistic inhibitory effect. 3. 3. Under aerobic conditions no rapid exchange diffusion of C 4-dicarboxylates is observed. 4. 4. Cells retain their accumulated metabolites under anaerobic conditions. Under these conditions uncouplers or energy-transfer inhibitors induce an efflux of metabolites. 5. 5. Under anaerobic conditions exchange of intracellular for extracellular dicarboxylates is observed. 6. 6. It is concluded from these results that in A. vinelandii Krebs-cycle intermediates are transported at the expense of energy. There are strong indications for a direct involvement of ATP in this energy-requiring process.