Size comparison of the Gram-negative plasmids with and without NAP gene homologs. (a) A total of 136 Gram-negative plasmids with one or more NAP gene homologs and 1246 Gram-negative plasmids without NAP gene homologs are shown by black and white bars, respectively. (b) Gram-negative plasmids with each NAP gene homolog are as follows: H-NS, red; HU, blue; IHF, green; Lrp, purple; MvaT, yellow; and NdpA, orange.