Exopolyphosphatase of Pseudomonas aeruginosa is essential for the production of virulence factors and its expression is controlled by NtrC and PhoB, acting at two interspaced promoters.

GALLARATO, LA; SACHEZ, DG; OLVERA, L; PRIMO, E; GARRIDO, MN; BEASSONI, PR; MORETT, E; LISA, AT

MICROBIOLOGY-UK

SOC GENERAL MICROBIOLOGY

Lugar: London; Año: 2014 vol. 160 p. 406 - 417

1350-0872

The exopolyphosphatase (Ppx) of Pseudomonas aeruginosa is encoded by the PA5241 gene (ppx). Ppx catalyzes the hydrolysis of inorganic polyphosphates (polyPs) to orthophosphate (Pi). We describe here the identification and characterization of the ppx promoter region and its regulation under environmental stress conditions. The role of Ppx in the production of several virulence factors is demonstrated by studies of a ppx null mutant. The results indicate that this gene is under the control of two interspaced promoters dually regulated by nitrogen and phosphate limitation. Under nitrogen limitation its expression is controlled from a σ54-dependent promoter activated by the response regulator NtrC. In contrast, under Pi limitation, its expression is controlled from a σ70 promoter activated by PhoB. The findings from the ppx null mutant demonstrate that Ppx is involved in the production of factors associated with both acute infection (e.g., motility-promoting factors, blue/green pigments production, quorum-sensing C6 C12 homoserine lactones) and chronic infection (e.g., rhamnolipids, biofilm formation). The molecular and physiological approaches used in this study indicate that P. aeruginosa consistently maintains appropriate levels of Ppx regardless of the environmental conditions. These results demonstrate the importance of this protein in maintaining the intracellular concentration of polyP within a narrow range. Therefore, Ppx appears to be essential for both the survival of the bacterium and the successful establishment of either acute or chronic infection in the host.