EXCEED THE SPACE PROVIDED. The long term goal of this research program is to uncover and understand mutational pathways, theDMA repair processes or avoidance mechanisms that counteract these pathways, and the consequences of defects in these systems. Our basic approach has often involved characterizing 'mutator strains' that have higher mutation rates than wild-type, and then determining the affected pathway or repair system. We have developed new approaches for the detection of mutators, and this has allowed us to define several new mutational pathways, including one that results from the overexpression of the EmrR represser of a multi- drug resistance efflux pump. Overexpressing a common represser is one way to detect mutational pathways that back each other up and thus require two knockouts to produce a mutator phenotype. We believe that this system acts to pump out mutagenic products of metabolism and represents the cell's first line of defense against mutagenesis. This proposal seeks to further character this novel system, and to characterizeother new mutaitonal pathways we have discovered. We will also utilize the just completed E. co//knockout collection, consisting of close to 4,300 strains, each carrying an in-frame deletion of one of the orfs in the E. co//genome, together with our own tools to screen for new mutational pathways. We will use genefusions to study the regulation of different repair genes and to characterizethe action of new mutators, and will use several pathogen or extremophile genomes (Bordetella pertussis, Campylobacterjejeuni, and Deinococcus radiodurans) as a source for genes that might provoke mutator pehnotypes in E. co//, and also that would complement different E. coli repair defects. We will also construct a system for studying mutagenesis in a pathogen such as B. pertussis. PERFORMANCE SITE ========================================Section End===========================================
