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J. Bacteriol., Nov 1995, 6411-6421, Vol 177, No. 22
W Jiang, WW Metcalf, KS Lee and BL Wanner
Two pathways exist for cleavage of the carbon-phosphorus (C-P) bond of
phosphonates, the C-P lyase and the phosphonatase pathways. It was
previously demonstrated that Escherichia coli carries genes (named phn)
only for the C-P lyase pathway and that Enterobacter aerogenes carries
genes for both pathways (K.-S. Lee, W. W. Metcalf, and B. L. Wanner, J.
Bacteriol. 174:2501-2510, 1992). In contrast, here it is shown that
Salmonella typhimurium LT2 carries genes only for the phosphonatase
pathway. Genes for the S. typhimurium phosphonatase pathway were cloned by
complementation of E. coli delta phn mutants. Genes for these pathways were
proven not to be homologous and to lie in different chromosomal regions.
The S. typhimurium phn locus lies near 10 min; the E. coli phn locus lies
near 93 min. The S. typhimurium phn gene cluster is about 7.2 kb in length
and, on the basis of gene fusion analysis, appears to consist of two (or
more) genes or operons that are divergently transcribed. Like that of the
E. coli phn locus, the expression of the S. typhimurium phn locus is
activated under conditions of Pi limitation and is subject to Pho regulon
control. This was shown both by complementation of the appropriate E. coli
mutants and by the construction of S. typhimurium mutants with lesions in
the phoB and pst loci, which are required for activation and inhibition of
Pho regulon gene expression, respectively. Complementation studies indicate
that the S. typhimurium phn locus probably includes genes both for
phosphonate transport and for catalysis of C-P bond cleavage.
Copyright © 1995, American Society for Microbiology
Molecular cloning, mapping, and regulation of Pho regulon genes for phosphonate breakdown by the phosphonatase pathway of Salmonella typhimurium LT2
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
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