OXIDATIVE SHIFT IN LATE STATIONARY PHASE BY PHOSPHATE CONCENTRATIONS IN Escherichia coli

SCHURIG-BRICCIO LA; RINTOUL MR; RODRÍGUEZ-MONTELONGO L; RAPISARDA VA

Mar del Plata

Congreso; Reunión anual de SAIB; 2007

Respiratory NADH dehydrogenase-2 (NDH-2) in Escherichia coli is a cupric-reductase encoded by ndh gene. The ndh is expressed in LB medium in exponential phase of growth, decaying during the stationary phase. However, we found that the ndh expression and NDH-2 membrane activity are maintained in late stationary phase by at least 37 mM phosphate salts. In order to study the cellular status in this physiological condition, we determined ROS production, concentration of NADH and NAD+, oxygen consumption and viability. Cells grown for 48 h in high phosphate media were more viable, presented higher oxygen consumption, had a lower NADH/NAD+ ratio (similar to exponential), and contained lower ROS than cells grown in low phosphate media. Moreover, we have observed that the decrease of ndh expression in low phosphate media was reversible when phosphate is added at 24h of culture. Our results show the importance of the phosphate concentration of the culture media in the regulation of gene expression, which can produce a drastic change in the metabolic pathways maybe associated to a protection effect against oxidative stress. Further studies should be done to understand the role of NDH-2 in late stationary phase under this growth condition.