Energy-dependence of the Assimilatory Nitrate Uptake in Azorhizobium caulinodans Strain IRBG 46
Nitrate assimilation by suspensions of Azorhizobium caulinodans strain IRBG 46, as determined by disappearance of nitrate ions from the external medium, displayed the requirement of readily utilizable carbon source. Nitrate uptake was blocked by the uncouplers of oxidative phosphorylation such as 2,4-dinitrophenol, carbonyl cyanide m-chlorophenyl hydrazone and by an inhibitor of ATPase, N, N — dicyclohexyl carbodiimide. The inhibition of nitrate assimilation in the absence of appropriate carbon source was not overcome by the non-physiological terminal electron donor ascorbate plus N-methyl phenazinium methyl sulphate, a substrate combination that allows electron transfer to O2 without the synthesis of ATP. These data suggest that transport of nitrate into the cell is directly dependent on ATP.
Key wordsAzorhizobium caulinodans nitrate uptake nitrate reductase energy dependence
Carbonyl cyanide m-chlorophenylhydrazone
N, N — dicyclohexyl carbodiimide
N-methyl phenazinium methyl sulphate
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- 3.Schloemer RH & Garret RH, J Bacteriol, 18 (1974) 259.Google Scholar
- 5.Thayer JR & Huffaker RC, J Bacteriol, 49 (1982) 198.Google Scholar
- 6.Revilla E, Llobell A & Paneque A, J Gen Microbiol, 32 (1985) 917.Google Scholar
- 7.Khanuja SPS, Current Sci, 61 (1991) 545.Google Scholar
- 8.Reddy AT & Lodha ML, Biochem Physiol Pflanzen, 181 (1986) 209.Google Scholar