coli, but also in almost all organisms exposed to oxygen, highlights that O 2. Presence of this highly evolved oxidative stress defence system in E. One of these peroxidases, the alkyl hydroperoxide reductase (Ahp) encoded by ahpCF genes, has been identified as the primary H 2O 2 scavenger at low H 2O 2 concentrations. coli also expresses several peroxidases reducing H 2O 2 to water rather than disproportionating it to O 2 and water as catalase does. scavenging and two haem-dependent catalases HPI and HPII involved in H 2O 2 scavenging, encoded by katG and katE, respectively.This is the case for Escherichia coli which expresses three different superoxide dismutases (SodA, SodB, and SodC), involved in O 2. and H 2O 2, and some bacteria harbour even several genes expressing enzymes of the same type.Almost all organisms harbour genes encoding enzymes scavenging O 2. In addition, iron is liberated during these reactions which can give rise to the formation of HO However, they are also toxic for bacteria likely because of their capacity to oxidize and destroy iron centres of some enzymes thus affecting cellular metabolism, , ]. and H 2O 2 do not readily react with biomolecules.is the most toxic of these ROS because reactivity with cellular molecules is only limited by diffusion., which is likely due to the difference in reactivity.Nature evolved enzymatic scavengers for the two former ROS but not for the HO ), hydrogen peroxide (H 2O 2) and hydroxyl radical (HO.This gives successively rise to superoxide (O 2. ROS are partially reduced oxygen species generated by a “one-by-one” electron transfer to molecular oxygen. However, our investigations allowed us to show that Npr is responsible for the degradation of approximately 45% of metabolically derived H 2O 2 which avoids accumulation of the peroxide to lethal concentrations.īacteria express anti-oxidative activities able to scavenge and neutralize reactive oxygen species (ROS). Mutants affected in one or several predicted anti-oxidative activities mentioned above showed that neither the peroxidases nor the catalase are implicated in the defence against peroxide challenges. Gene expression analyses showed that npr and kat genes are especially and significantly induced in cells treated with hydrogen peroxide (H 2O 2) and cumene hydroperoxide (CuOOH), which suggested an important function of these enzymes to protect E. This healthcare-associated pathogen harbours genes encoding putative NADH peroxidase (Npr), alkyl hydroperoxide reductase (AhpCF), glutathione peroxidase (Gpx) and manganese-dependent catalase (Mn-Kat). In this work, the physiological roles of the primary peroxide scavenging activities of Enterococcus faecium AUS0004 strain were analysed.

Clc genomics workbench map to reference