RT Journal Article
SR Electronic
T1 Neo-formation of chromosomes in bacteria
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 264945
DO 10.1101/264945
A1 Olivier Poirion
A1 Bénédicte Lafay
YR 2018
UL http://biorxiv.org/content/early/2018/02/13/264945.abstract
AB The genome of bacteria is classically separated into the essential, stable and slow evolving chromosomes and the accessory, mobile and rapidly evolving plasmids. This distinction was blurred with the characterization of multipartite genomes constituted of a “standard” chromosome and additional essential replicons integrated in the cell cycle. Although these (“megaplasmids”, “secondary chromosomes” or “chromids”) are considered to be adapted plasmids, their true nature and evolution are yet to be determined. We performed a global comparative genomic analysis using all available bacterial genomes using genes functionally related to the genomic information inheritance systems as parameters. We show that the bacterial replicons can be discriminated into chromosomes, plasmids, and another class of genomic elements that we tentatively name “neochromosomes” for their functioning as chromosomes and their coming into existence secondarily to the classical chromosome. Whereas some neochromosomes are clearly plasmidic in origin (most frequent case), a few might be deriving from the cleavage of an ancestral “true” chromosome.