RAPISARDA Viviana Andrea
congresos y reuniones científicas
Protection against oxidative stress depends on phosphate concentration in Escherichia coli stationary phase
SCHURIG-BRICCIO, L. A.; RODRÍGUEZ-MONTELONGO, L.; RINTOUL, M. R.; RAPISARDA, V. A.
Congreso; VI Meeting of the Society for Free Radical Biology and Medicine, South American Group (Free Radicals and Antioxidants in Chile); 2009
Society for Free Radical Biology and Medicine
E. coli gradually decline the capacity to resist oxidative stress during stationary phase. However, we have previously reported that, in stationary phase E. coli cells grown in media containing at least 37 mM phosphate, maintained ndh expression, having high viability and low NADH/NAD+ ratio. Here, the effect of different phosphate concentrations in the growth media was evaluated. We assayed several respiratory and defense genes expression, reactive oxygen species (ROS) production, damage to lipids and proteins, and the tolerance to H2O2 and copper in stationary E. coli cells. Media with different phosphate concentrations: LPM, limited phosphate medium (0.1 mM); SPM, sufficient phosphate medium (2 mM); and HPM, high phosphate medium (37 mM) were used. Interestingly, cells grown in LPM and HPM maintained a higher viability than SPM cells until 96 h of culture. Nevertheless, the expression of several aerobic respiratory genes (ndh, nuoAB, sdhC, cydA and ubiC) and defense genes (katG and ahpC) were maintained until 96 h of culture only in HPM. Additionally, in this medium, ROS production was minimal and consequently the levels of thiobarbituric acid-reactive substances (TBARS) and protein carbonylation were lower than the expected for stationary cells. The ROS production and the TBARS levels were similar in LPM and in SPM. It is important to note that a high expression of defense genes (katG and ahpC) was observed in LPM stationary cells. Together, our results indicate that cells grown in HPM exhibit advantages to resist endogenous and exogenous (H2O2 or copper) oxidative stress in stationary phase.