Second Chromosomes and Megaplasmids in Bacteria

摘要: This chapter reviews some aspects of the many major secondary DNA replicons that have been characterized from organisms possess multireplicon genomes. Nonprimary are often referred to as chromosomes if they essential for cell viability or megaplasmids. A modern source ambiguity in genomic biology is whether certain represent megaplasmids second chromosomes. Multircplicon genomes bacteria could conceivably arise by a number mechanisms, but two general mechanisms seem most plausible. replicon may derive an ancestral chromosome via excision event where excised possesses origin replication either duplicated copy oriC region second, redundant was previously resident on part chromosome. Chromosome I has typical other bacterial chromosomes, and encodes dnaA, dnaN, recF, gyrA genes. greater proportion II also devoted genes encoding transporters solute binding proteins enzymes required central intermediary metabolism. The linear exoC synthesis several surface polysaccharides cellulose host attachment. Copies amino acids enzyme cofactors carried uniquely megaplasmid flagellar