THE GLOBAL REGULATOR CREC OF Escherichia coli AFFECTS THE INTRACELLUAR REDOX BALANCE AND ITS ABSENCE INCREASES SUCEPTIBILITY TO OXIDATIVE STRESS.

MANUEL S. GODOY; MARIA JULIA PETTINARI

Buenos Aires

Congreso; X Congreso de la Sociedad Argentina de Microbiología General (SAMIGE 2014); 2014

Sociedad Argentina de Microbiología General

The survival of an organism depends, at least in part, on its ability to sense and respond to changes in the environment. In bacteria, changes in the physical and nutritional characteristics of the environment generate immediate responses, controlled through the regulation of sets of genes in response to specific environmental stimuli and metabolic signals.In this work we studied the effect of CreC, a global regulator, in different aspects of bacterial fisiology, such as redox balance, oxygen consumption, and oxidative stress, in conditions in which CreC is active (M9 mineral media suplemented with glucouse and low oxygen availability).In the firsts attemps to caracterize the metabolic profile of strains with mutations in creC , a cleardecrease of the intracellular redox state could be observed in the ∆creC strain (DC1060) when compared to the wild type strain (K1060), evidenced through the [ethanol]/[acetate] rate. This results led us to test the growth of these strains in M9 glucouse with toluidine blue. In this media, cells with a lower respiratory activity tend to produce more reactive oxygen species (ROS) due to the dye present in the media, giving smaller colonies. Surprisingly, the mutant strain, which was supposed to have a more oxidative intracellular environment, gave rise to smaller colonies than the wild type. To see if the absence of CreC was the cause of the higher ROS suscenpitibility, strains were grown in the presence of oxidative chemicals, such as hydrogen peroxide and paraquat, to determine the minimum inhibitory concentration (CIM). In these experiments, we could corroborate that the absence of CreC augmented the susceptibility of the cells to oxidative stress. Finally we measured the rate of reduced/oxidized cofactors [NAD(P)H/NAD(P)+] to confirm the oxidized intracelluar state of ∆creC mutants. Strain DC1060 was observed to have a lower NADH/NAD+ rate than the K1060 strain in oxygen limiting conditions.These results suggest that CreC affects the redox balance, most probably by affecting carbon flux in the fermentative routes. As the molecular mechanisms involved in the response of ROS production require cofactors, the lower NADH/NAD+ rate observed in strain DC1060 could be the reason for the increased susceptibility to oxidative chemicals.