coli belonging to different pathovars and phylogenetic groups was

coli belonging to different pathovars and phylogenetic groups was nearly similar in pooled human urine. The slow growth of a few isolates could reflect the RpoS polymorphism in E. coli population [43, 44]. Sotrastaurin molecular weight Cultures were grown in microaerophilic conditions (see Methods), where oxygen levels are similar to those in the human urinary tract [18, 45]. This reduction in oxygen content leads to a redistribution of metabolic fluxes between www.selleckchem.com/products/poziotinib-hm781-36b.html fermentation and respiration [46]. Such a shift may decrease the respiratory chain-mediated generation of ROS. Moreover, in our culture

conditions, autoxidizable enzymes such as L-aspartate oxidase and fumarate reductase should not contribute significantly to the formation of H2O2. However, metabolic reactions that generate nearly two-thirds of H2O2 are not yet identified [47]. Therefore, we can expect that changes in metabolic fluxes generate different ROS levels. Analysis of metabolic capabilities in a collection of 153 E. coli natural isolates [48] and of gene expression in strains ABU 83972 and CFT073 grown exponentially R428 in urine [49] revealed significant differences in their metabolic capacities. These metabolic changes could therefore generate different ROS levels in our isolates. Urine is a complex growth medium

and E. coli must adapt to stress imposed by this tough environment. The high osmolality, high urea concentration, low pH and the limitation of certain components could provoke an oxidative response. To protect from these highly

reactive intermediates, cells possess a defense system consisting of both enzymatic and non- enzymatic antioxidants that scavenge them. Nevertheless, under several situations, the rate of generation of ROS exceeds that of their removal and oxidative stress occurs. The levels Osimertinib nmr of damage products accumulated (estimated as TBARS concentration) mirror the intensity of oxidative stress. Our results demonstrate that E. coli strains can respond very differently to stress imposed by urine. TBARS measurements revealed that many E. coli are exposed to ROS during exponential growth in urine. Surprisingly, this is the case of ABU strain 83972 that is very well adapted to growth in the urinary tract [11]. In contrast, two other ABU strains 38 and 62, as UTI89, Sakai and MG1655 showed a lower oxidative damage to lipid. No clear correlation between ROS level and the phylogroups or pathogenic group was apparent. ABU isolates form a heterogenous group. Individual ABU strains display many differences between them in their genome contents and in virulence-associated genes such as LPS, microcin, aerobactin, and mobility [11, 27]. Interestingly, our study shows that the two ABU strains (38 and 62) belonging to the group B1, differ from other by the low ROS production in urine. The commensal-like ABU 83972 strain and the pathogenic strain CFT073 are very closely related and belong to the same B2 subgroup II [25], or to the same sequence type 73 clonal group [4].

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