Low oxidative damage in Escherichia coli stationary phase by a phosphate-dependent genes expression

LICI A. SCHURIG-BRICCIO; MARÍA R. RINTOUL; VIVIANA A. RAPISARDA

Villa Carlos Paz (Córdoba)

Congreso; Reunión anual SAIB; 2008

Bacteria have developed antioxidant defense systems for the protection against reactive oxygen species (ROS). However, these systems may be insufficient and ROS can produce oxidative damage. E. coli capacity to resist oxidative stress gradually declines during stationary phase. We have previously reported that E. coli cells grown in media with phosphate above a critical concentration (>37 mM) had high viability and low NADH/NAD+ ratio in stationary phase. Here, we analyse the relationship between oxidative stress and the defense genes expression in stationary phase cells grown under this condition. The endogenous stress (as cellular ROS production) and the oxidative damage to lipids (as TBARS) and proteins (as carbonyl groups generation) were determined. The ROS production was minimal and consequently the levels of TBARS and protein carbonylation were lower than expected for stationary phase. In addition, cells were highly resistant to exogenous stress induced by H2O2 . Expression of sodA, katG and ahpC was also assayed. Interestingly, katG and ahpC expressions were maintained high in late stationary phase. The presence of catalase and alkyl hydroperoxide reductase may explain the high viability and the low oxidative damage. Together, cells grown with high phosphate display advantages against oxidative stress in stationary phase.