Identification and Characterization of the Replication Region of the Virulence Plasmid pEIB202 in.

Abstract

is the causative agent of edwardsiellosis, which has caused enormous economic losses worldwide. In our previous research, an attenuated live vaccine WED based on the virulent strainEIB202 can effectively protect turbots against edwardsiellosis via intraperitoneal injection, while vaccination by immersion exhibits a weaker effect. During the development of the immersion vaccine, we surprisingly found the counts of ΔpEIB202/ EIB202 colonized on zebrafish were 100 times lower than those of EIB202. However, pEIB202 carries 53 predicted ORFs and has several copies inEIB202, impeding the study of its function. Thus the replication region is located at a 1 980 bp fragment (from 18 837 to 20 816 bp), containing a transcriptional repressor and a replication protein. Moreover, the minimal replication plasmid, named pRep-q77, has low copies in bothand, but is more stable inthan in. This work lays a foundation for further examination of the function of the virulence plasmid pEIB202.