The disruption of a gene encoding a putative arylesterase impairs pyruvatedehydrogenase complex activity and nitrogen fixation in Sinorhizobium meliloti
Mj. Soto et al., The disruption of a gene encoding a putative arylesterase impairs pyruvatedehydrogenase complex activity and nitrogen fixation in Sinorhizobium meliloti, MOL PL MICR, 14(6), 2001, pp. 811-815
Nitrogen-fixing Sinorhizobium meliloti cells depend upon dicarboxylic acids
as carbon and energy sources. The metabolism of these intermediate compoun
ds of the trichloroacetic acid cycle is dependent upon the availability of
acetyl-coenzyme A (CoA), In bacteroids, the combined activities of malic en
zymes and pyruvate dehydrogenase (PDH) have been proposed to be responsible
for the anaplerotic synthesis of acetyl-CoA. We obtained a S. meliloti mut
ant strain, PD3, in which a Tn5 insertion led to a significant decrease in
the overall PDH activity. The genetic characterization of this mutant revea
led 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, w
hich strengthens the physiological importance of PDH activity ill the symbi
osis of S. meliloti with alfalfa plants.