Characterization of the Rhizobium (Sinorhizobium) meliloti high- and low-affinity phosphate uptake systems.

Abstract

Genetic studies have suggested that Rhizobium (Sinorhizobium) meliloti contains two distinct phosphate (Pi) transport systems, encoded by the phoCDET genes and the orfA-pit genes, respectively. Here we present data which show that the ABC-type PhoCDET system has a high affinity for Pi (Km, 0.2 microM) and that Pi uptake by this system is severely inhibited by phosphonates. This high-affinity uptake system was induced under Pi-limiting conditions and was repressed in the presence of excess Pi. Uptake via the OrfA-Pit system was examined in (i) a phoC mutant which showed increased expression of the orfA-pit genes as a result of a promoter-up mutation and (ii) a phoB mutant (PhoB is required for phoCDET expression). Pi uptake in both strains exhibited saturation kinetics (Km, 1 to 2 microM) and was not inhibited by phosphonates. This uptake system was active in wild-type cells grown with excess Pi and appeared to be repressed when the cells were starved for Pi. Thus, our biochemical data show that the OrfA-Pit and PhoCDET uptake systems are differentially expressed depending on the state of the cell with respect to phosphate availability.

7 Figures and Tables

Statistics

0100200'99'01'03'05'07'09'11'13'15'17
Citations per Year

618 Citations

Semantic Scholar estimates that this publication has 618 citations based on the available data.

See our FAQ for additional information.

Cite this paper

@article{Voegele1997CharacterizationOT, title={Characterization of the Rhizobium (Sinorhizobium) meliloti high- and low-affinity phosphate uptake systems.}, author={Ralf Thomas Voegele and Sabine Bardin and Turlough M Finan}, journal={Journal of bacteriology}, year={1997}, volume={179 23}, pages={7226-32} }