COMPARATIVE GENOME ARCHITECTURE AND DYNAMICS IN BACTERIA

This article reviews current knowledge about the organization of bacte rial genomes, of which a number of components (replicons), namely chro mosomes, plasmids and prophages, have been well characterized. The his torical position of the acceptance of the idea of circularity and unit copy number of replicons in bacterial cells has been readdressed by n ew methods of genome analysis, particularly pulsed-field gel electroph oresis, which have facilitated identification of variation in replicon number and distinction whether the replicons are circular or linear D NA structures. Much has also been learnt about the origins of DNA repl ication in replicons and how they function via the controlling role of specific proteins or RNA. A related aspect is the problem of how the replication products are stabilized, segregated and partitioned into d aughter cells at cell division. Our understanding. of replicons has al so been improved by application of state-of-the-art computer software methods of comparative DNA and protein sequence analysis. This knowled ge has provided insights into the fundamental nature of these processe s and their origin and evolution in single-cell and multicellular orga nisms.