The bacterial nucleoid: a highly organized and dynamic structure.

Recent advances in bacterial cell biology have revealed unanticipated structural and functional complexity, reminiscent of eukaryotic cells. Particular progress has been made in understanding the structure, replication, and segregation of the bacterial chromosome. It emerged that multiple mechanisms cooperate to establish a dynamic assembly of supercoiled domains, which are stacked in consecutive order to adopt a defined higher-level organization. The position of genetic loci on the chromosome is thereby linearly correlated with their position in the cell. SMC complexes and histone-like proteins continuously remodel the nucleoid to reconcile chromatin compaction with DNA replication and gene regulation. Moreover, active transport processes ensure the efficient segregation of sister chromosomes and the faithful restoration of nucleoid organization while DNA replication and condensation are in progress. (c) 2005 Wiley-Liss, Inc.