The Global Regulator Crec of Escherichia coli Responds to Different Oxygen Availability Affecting LDH and ACK Activity.

MANUEL S. GODOY; MARIA JULIA PETTINARI

Nueva Orleans

Congreso; 115 Congreso anual de la Sociedad Americana de Microbiologia (ASM General Meeting 2015); 2015

Sociedad Americana de Microbiologia (ASM General Meeting 2015)

Background. Global regulators in E. coli work hierarchically to control a complex network of genes in response to environmental conditions and resource availability. CreBC is a two-component system involved in the regulation of carbohydrate catabolism CreC is the sensor molecule, that activates the CreB regulator in response to carbon source and oxygen availability.Materials. The relationship between some physiological parameters and oxygen availability was studied in three strains: K1060 (wt) DC1060 (ΔcreC) and K1060C (creC510, constitutive). Metabolite production (acetate, lactate, succinate, formate, and ethanol) and enzymatic activity of two key fermentation enzymes (LDH and ACK), were measured in three diferent oxygen availablity conditions, determined by the agitation speed and the volume of the flask to media volume ratio using mineral medium (M9) supplemented with glucose.Results. No significant differences were observed between strains in high aerobiosis, with the exception of acetate, the main acid secreted. In microaerobiosis, DC1060 produced more acetate and less lactate than K1060. DC1060 had 50% more ACK and 40% less LDH activities compared to the wild type strain, showing good correlation between enzyme activity and metabolite concentration. In anaerobiosis, acetate production decreased for all strains compared to low aerobiosis, but less in the deletion mutant. Once again, ACK activity was 60% higher in DC1060 than in K1060, but surprisingly in anaerobioisis LDH activity and lactic acid production had the opposite trend from that observed in low aerobiosis: they were higher for DC1060 than for K1060. Other metabolites that were affected by the absence of CreC were formate and succinate, both of which showed increased levels in the deletion mutant compared to the wild type. Experiments performed using different mutants (∆creB, ∆creC and ∆creBC) revealed no differences among them, ruling out the possibility that the effects observed could be due to cross-talk of CreC with other regulators. Conclusion. These results show that the effects of CreC over metabolism seem to be different depending on oxygen availability, and that this regulation is mediated by CreB. CreC was shown to affect the activity of both ACK and LDH, explaining at least in part the observed metabolic effects.