Nucleoid organization and the maintenance of DNA integrity in E-coli, B-subtilis and D-radiodurans

For enzymatic activities to be effectively carried out, basic prerequisites must be met. Many enzymatic tasks require continuous consumption and dissipation of energy, sometimes in massive amounts. Some activities, such as DNA replication, transcription, and repair through homologous recombination rely upon templates that provide the information required for these transactions. Yet, circumstances where intracellular energy pools are severely depleted, or where intact templates are not available, frequently occur. Moreover, the fact that in order to reach their targets, enzymes must cope with an extremely crowded and viscous cellular milieu that drastically slows down their diffusion is often neglected. These impediments are particularly evident under stress conditions such as prolonged starvation or continuous exposure to DNA-damaging agents. Here we survey recent studies, which imply that when enzymatically-mediated DNA repair pathways are hindered, alternative strategies are deployed, whose common denominator is the reorganization of bacterial nucleoids into morphologies that promote DNA repair and protection. (c) 2006 Elsevier Inc. All rights reserved.