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

Abstract

The exopolyphosphatase (Ppx) of Pseudomonas aeruginosa is encoded by the PA5241 gene (ppx). Ppx catalyses the hydrolysis of inorganic polyphosphates to orthophosphate (P i ). In the present work, we identified and characterized the promoter region of ppx and its regulation under environmental stress conditions. The role of Ppx in the production of several virulence factors was demonstrated through studies performed on a ppx null mutant. We found that ppx is under the control of two interspaced promoters, dually regulated by nitrogen and phosphate limitation. Under nitrogen-limiting conditions, its expression was controlled from a s 54 -dependent promoter activated by the response regulator NtrC. However, under P i limitation, the expression was controlled from a s 70 promoter, activated by PhoB. Results obtained from the ppx null mutant demonstrated that Ppx is involved in the production of virulence factors associated with both acute infection (e.g. motility-promoting factors, blue/green pigment production, C6-C12 quorumsensing homoserine lactones) and chronic infection (e.g. rhamnolipids, biofilm formation). Molecular and physiological approaches used in this study indicated that P. aeruginosa maintains consistently proper levels of Ppx regardless of environmental conditions. The precise control of ppx expression appeared to be essential for the survival of P. aeruginosa and the occurrence of either acute or chronic infection in the host.

The potential for polyphosphate metabolism in Archaea and anaerobic polyphosphate formation inMethanosarcina mazei

“…When compared to the control cells at the end of the starvation phase (T4) the expression of ppk1 was 4.2-fold lower in the treated cells, rising to 3.7-fold higher at after overplus (T6). Upregulation of ppk1 expression would therefore appear to begin after the addition of Pi to Pi-starved M. mazei cells and thus differ from the majority of previous bacterial overplus studies where ppk (and ppx) expression has been shown to begin during the Pi starvation phase, under the control of the PHO regulon [57][58][59][60][61][62][63] .…”

Pseudomonas aeruginosaExopolyphosphatase Is Also a Polyphosphate: ADP Phosphotransferase

“…We have recently demonstrated the involvement of Ppx in the pathogenesis of P. aeruginosa [ 8 ]. This finding led us to investigate in greater detail the enzyme from a biochemical approach.…”

“…As the NH 4 + concentration is limited or in the presence of a nonpreferential nitrogen source (amino acids, choline, etc. ), the activation of pa Ppx is at transcriptional level since the expression of the ppx gene is under the control of the global regulator NtrC [ 8 ]. On the other hand, with a good availability of nitrogen in the environment, NH 4 + directly stimulates the enzymatic activity and the bacteria obtain energy to start their growth.…”

“…However, little is known about the relation between Ppx and its possible role in the pathogenesis of this bacterium [ 3 , 6 , 7 ]. We have recently confirmed that Ppx is relevant for pathogenesis in P. aeruginosa [ 8 ], due to the fact that the ppx null mutant was defective in the production of factors associated to both acute infection (e.g., motility-promoting factors, blue/green pigments production, and quorum-sensing C6–C12 homoserine lactones) and chronic infection (e.g., rhamnolipids and biofilm formation). Thus, there is enough evidence that both Ppk and Ppx as well as polyP balance contribute to the pathogenesis of P. aeruginosa .…”

Purification, crystallization and X-ray crystallographic analysis of a putative exopolyphosphatase fromZymomonas mobilis

“…An imbalance between poly-P synthesis and degradation can result in fluctuations of poly-P by 100-fold to 1000-fold; a study in Escherichia coli showed that high levels of alarmones have no effect on PPK activity but inhibit PPX activity, resulting in large accumulations of poly-P (Kuroda et al, 1997). PPX enzymes are also essential for virulence, infectivity, resistance, biofilm formation, swimming and swarming motility, and sporulation efficiency (Zhang et al, 2010;Gallarato et al, 2014;Shi et al, 2004;Thayil et al, 2011;Malde et al, 2014).…”