1887

Abstract

Two component regulatory systems are key elements in the control of bacterial gene expression in response to environmental perturbations. The SenX3–RegX3 system is implicated in the control of phosphate uptake in and is reported to be essential in , but not in . We attempted to construct complete operon deletion strains of ; initially we found that the operon could only be deleted when another functional copy was provided. Using a strain in which the only functional copy of the operon was present on an integrating plasmid, we attempted to replace the functional copy with an empty vector. Surprisingly, we obtained strains in which the functional copy had been deleted from the chromosome at a low frequency. We deleted the gene in a similar fashion, but it was not possible to delete alone. To identify possible compensatory mutations we sequenced the whole genome of two deletion strains and the wild-type. A synonymous single nucleotide polymorphism (SNP) in a lipoprotein was found in all deletion strains, but not the parental strains, and a frameshift mutation in was identified in three of the four deletion strains. Operon deletion strains were more sensitive to phosphate limitation, showing a reduced ability to grow at lower phosphate concentrations. The operon was able to functionally complement the growth phenotype in under phosphate-replete conditions, but not under low phosphate conditions, reinforcing the difference between the two species. Our data show that, in contrast with previous reports, it is possible to delete the operon in , possibly due to the accumulation of compensatory mutations, and that the deletion does affect growth in phosphate.

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2012-11-01
2019-10-24
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