a mate-family efflux pump rescues the escherichia coli 8-oxoguanine-repair-deficient mutator phenotype and protects against h2o2 killing一个mate-family射流泵救援大肠杆菌8-oxoguanine-repair-deficient突变表型和防止过氧化氢.pdfVIP

A MATE-Family Efflux Pump Rescues the Escherichia coli 8-Oxoguanine-Repair-Deficient Mutator Phenotype and Protects Against H2O2 Killing 1 ´ 1 2 ´ ´ 1 Javier R. Guelfo , Alexandro Rodrıguez-Rojas , Ivan Matic , Jesus Blazquez * ´ ´ ´ 1 Departamento de Biotecnologıa Microbiana, Centro Nacional de Biotecnologıa-Consejo Superior de Investigaciones Cientıficas (CSIC), Madrid, Spain, 2 INSERM, 1001, ´ ´ ´ Faculte de Medicine, Universite Paris Descartes, Paris, France Abstract Hypermutation may accelerate bacterial evolution in the short-term. In the long-term, however, hypermutators (cells with an increased rate of mutation) can be expected to be at a disadvantage due to the accumulation of deleterious mutations. Therefore, in theory, hypermutators are doomed to extinction unless they compensate the elevated mutational burden (deleterious load). Different mechanisms capable of restoring a low mutation rate to hypermutators have been proposed. By choosing an 8-oxoguanine-repair-deficient (GO-deficient) Escherichia coli strain as a hypermutator model, we investigated the existence of genes able to rescue the hypermutable phenotype by multicopy suppression. Using an in vivo-generated mini-MudII4042 genomic library and a mutator screen, we obtained chromosomal fragments that decrease the rate of mutation in a mutT-deficient strain. Analysis of a selected clone showed that the expression of NorM is responsible for the decreased mutation rate in 8-oxoguanine-repair-deficient (mutT, mutY, and mutM mutY) strains. NorM is a member of the multidrug and toxin extrusion (MATE) family of efflux pumps whose role in E.