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Appl. Environ. Microbiol., 11 1995, 3992-3997, Vol 61, No. 11
I Hernandez-Lucas, MA Pardo, L Segovia, J Miranda and E Martinez-Romero
Two genes encoding citrate synthase, a key enzyme in the Krebs cycle, have
been found in Rhizobium tropici. One of them is in the bacterial
chromosome, while the other is in the symbiotic plasmid. We sequenced the
chromosomal gene and found that it is very similar to the previously
reported plasmidic gene sequence in its structural region but not in its
regulatory region. The chromosomal gene is able to complement an
Escherichia coli citrate synthase mutant. In R. tropici, a mutant in the
chromosomal citrate synthase gene has a diminished citrate synthase
activity (in free-living bacteria), a diminished nodulation capacity, and
forms nitrogen-fixing nodules. In contrast, the citrate synthase double
mutant forms ineffective nodules devoid of bacteroids and forms less
nodules than the single chromosomal mutant. It is inferred that both genes
are functional and required during the nodulation process in R. tropici.
Copyright © 1995, American Society for Microbiology
Rhizobium tropici chromosomal citrate synthase gene
Departamento de Genetica Molecular, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos, Mexico.
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