Fig. 5.

Plot of G + C contents of 209 plasmids and their host chromosomes. Each point represents a plasmid-chromosome pair from 209 prokaryotes. To minimize the bias in the numbers of sequenced organisms and replicons available in public databases (e.g., thousands of genome projects for Escherichia coli, and multireplicons for Borrelia species), RefSeq data for completely sequenced prokaryotes that consist of one chromosome and plasmid were retrieved on April 17, 2017 from a list of all selected representative prokaryotic genomes (ftp://ftp.ncbi.nlm.nih.gov/genomes/GENOME_REPORTS/prok_representative_genomes.txt). The G + C contents of plasmids tend to be lower than (and are correlated with) those of the host chromosomes.