RAPISARDA Viviana Andrea
congresos y reuniones científicas
Phosphate-enhanced stationary phase fitness of E. coli is related to polyphosphate level
SCHURIG-BRICCIO, L. A.; FARÍAS, R. N.; RINTOUL, M. R.; RAPISARDA, V. A.
San Miguel de Tucumán, Tucumán, Argentina
Congreso; XLV Annual Meeting of SAIB; 2009
Cellular polyphosphate (polyP) level plays an important role in diverse basic metabolism and in stress responses. The main enzymes associated to polyP metabolism are polyphosphate kinase (encoded by ppk) and exopolyphosphatase (ppx). We have previously shown that E. coli cells grown in media containing >37 mM phosphate displayed an unusual stationary phase. They maintained the expression of several respiratory and defense genes, had high viability, low oxidative damage and elevated tolerance to exogenous H2O2. Here, we examined the relationship between the medium´s phosphate concentration, the intracellular polyP level and the stationary phase events. The polyP level was determined in cells of wild type and ppk ppx mutant strains grown in media with different phosphate concentrations. This level was maintained up to 72 h only in M9-grown wild-type strain. The ppk ppx mutant exhibited low polyP level regardless of the medium used or growth stage. In the wild type, the expression of sdhC, ubiC, and rpoS genes, the enzymatic activities of NDH-2, SDH and catalase and the tolerance to H2O2 remained high in stationary phase, but in the ppk ppx mutant strain they progressively decreased. Our results demonstrated that a critical phosphate concentration maintains in stationary phase a high polyP level, which could account for the enhanced stationary phase fitness in E. coli.