Mechanism of replication and copy number control of plasmids in gram-positive bacteria.

Abstract

Ever since plasmids were first discovered, they have served as important model systems for the study of various biological processes, including DNA replication, gene expression, recombination and gene transfer. Most of the earlier intensive studies carried out with plasmids of Gram-negative bacteria, such as ColEl, R6K, RK2 and plasmids of the incFII family, revealed that they replicated by either a unidirectional or bidirectional theta-type mechanism. These studies also provided the first evidence of an antisense mechanism for the regulation of DNA replication in the case of the ColEl plasmid (1). Similarly, initiator-dependent “handcuffing” was shown to be responsible for the regulation of replication of R6K, RK2 and PI plasmids (2–4). Studies with E. coli plasmids also identified directly repeated sequences (iterons) as elements critical in the initiation and regulation of DNA replication (5–8). In recent years, significant progress has also been made in our understanding of the biology of plasmids in Gram-positive bacteria. These studies have revealed some similarities as well as significant differences in the mechanism of replication and copy number control of these plasmids as compared from those of the Gram-negative organisms. In this review, the replication and copy number control of plasmids in Gram-positive bacteria is discussed with emphasis on the molecular aspects.KeywordsPlasmid Copy NumberLeader RegionRolling CirclePlasmid ReplicationStreptococcus AgalactiaeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.