DNA Repair Systems

Abstract

Escherichia coli has served as the principal model for investigations into DNA repair mechanisms. The DNA repair systems identified in this paradigm have also been discovered in most other organisms studied. This chapter attempts to look at these repair systems with respect to differentiation processes and developmental biology as studied in the gram-positive bacterium Bacillus subtilis. Originally, DNA repair systems were considered integral parts of an organism's ability to survive the effects of environmental insults and metabolic processes. However, as the molecular characterization of these repair systems proceeded it became obvious that in addition to determining mutation frequency and cell survival, DNA repair systems also play important roles in viral activation, DNA replication, genetic recombination, metabolism, and cancer. In order to investigate systematically the interrelationship(s) between DNA repair systems and these other phenomena, an appropriate model system must be identified. These systems are generally linked in their expression and activity with one or more of the developmental states that have been identified for the bacterium. It is in the elucidation of this linkage that B. subtilis becomes a critical model for the understanding of how organisms respond at the molecular level to stressful situations. Similar characterizations of these repair systems in other gram-positive bacteria, especially among the extremely resistant bacteria, will determine whether or not B. subtilis represents a paradigm for gram-positive bacteria or for bacteria that have distinct developmental cycles.