This volume looks at the evolution of the topo field over the last year and discusses how DNA topoisomerases are directly and indirectly involved in numerous cellular processes. The chapters in this book cover various topics, such as type 1 topos with an evolutionary perspective; antimicrobial agents targeting topos; experimental protocols related to DNA topology, including a basic technique to measure DNA supercoiling in bacteria; protocols for in vitro studies, including assays to detect RNA topo activity; topo inhibitors; and a study of plasmid-mediated quinolone resistance in bacteria. Written in the highly successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls. Cutting-edge and comprehensive, DNA Topoisomerases: Methods and Protoc ols is intended for specialists and non-specialists with an overview of selected hot topics in the field, and the latest protocols to study DNA topology, topoisomerases functions and inhibition by various compounds.