The disruption of a gene encoding a putative arylesterase impairs pyruvate dehydrogenase complex activity and nitrogen fixation in Sinorhizobium meliloti.
Nitrogen-fixing Sinorhizobium meliloti cells depend upon dicarboxylic acids as carbon and energy sources. The metabolism of these intermediate compounds of the trichloroacetic acid cycle is dependent upon the availability of acetyl-coenzyme A (CoA). In bacteroids, the combined activities of malic enzymes and pyruvate dehydrogenase (PDH) have been proposed to be responsible for the anaplerotic synthesis of acetyl-CoA. We obtained a S. meliloti mutant strain, PD3, in which a Tn5 insertion led to a significant decrease in the overall PDH activity. The genetic characterization of this mutant revealed that the transposon is located at the 3' end of a gene (ada) encoding a putative arylesterase. The mutant PD3 is deficient in nitrogen fixation, which strengthens the physiological importance of PDH activity in the symbiosis of S. meliloti with alfalfa plants.
Soto
M J
MJ
Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Granada, Spain.
Sanjuan
J
J
Olivares
J
J
D000105:Acetyl Coenzyme A / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism; D004251:DNA Transposable Elements; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics* / Q000502:physiology; D010941:Plant Tumors / Q000209:etiology; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D016962:Sinorhizobium meliloti / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D019895:Transposases / Q000235:genetics / Q000378:metabolism
D004251:DNA Transposable Elements; D011768:Pyruvate Dehydrogenase Complex; D000105:Acetyl Coenzyme A; D019895:Transposases; D002265:Carboxylic Ester Hydrolases; C019734:arylesterase