Copper-tolerance in E. coli mediated by polyphosphate level and Pit metal/phosphate transporter

GRILLO-PUERTAS, M.; SCHURIG-BRICCIO, L. A.; RODRÍGUEZ-MONTELONGO, L.; RINTOUL, M. R.; RAPISARDA, V. A.

San Miguel de Tucumán, Tucumán, Argentina

Congreso; XLV Annual Meeting of SAIB; 2009

SAIB

We have previously shown that E. coli cells grown in media containing >37 mM phosphate maintained in stationary phase a high polyphosphate (polyP) level and enhanced-cellular fitness. Cellular polyP level plays an important role in basic metabolism and in stress responses. The main enzymes associated to polyP metabolism are polyphosphate kinase (PPK) and exopolyphosphatase (PPX). Metals tolerance has been correlated with polyP level in several microorganisms. This tolerance may be due to the metals sequestration by the polymer and to the activation by metals of PPX, which degrades polyP leading to the formation of metal-phosphate complexes to be exported by the inorganic phosphate transporter (Pit) system. However, these events have not been described yet in E. coli for copper. Here, we analyzed the copper-tolerance of cells grown in media with different phosphate concentrations and their relationship with the polyP level. A high copper-tolerance was shown in stationary-cells grown in high phosphate medium. On the other hand, the intracellular polyP level was decreased when cells were incubated with CuSO4. In stationary phase, the pitA mutant strain grown in high phosphate medium was more sensitive to CuSO4 than the wild type strain. The copper-tolerance in stationary phase could be due to the polyP degradation and the later transport of metal-phosphate complexes through Pit.