Second Chromosomes and Megaplasmids in Bacteria

This chapter reviews some aspects of the many major secondary DNA replicons that have been characterized from organisms that possess multireplicon genomes. Nonprimary replicons are often referred to as secondary chromosomes if they are essential for cell viability or as megaplasmids. A modern source of ambiguity in genomic biology is whether certain replicons represent megaplasmids or second chromosomes. Multircplicon genomes in bacteria could …