ABSTRACT
Objective To study the differences of chromosomal structure among Yersinia pestis strains isolated from China,and to investigate the reasons of chromosomal rearrangement events occurred in Yersinia pestis as well as the possibility of strain identification and phylogenetic analysis based on the chromosomal rearrangement features.Methods According to the genome sequence data downloaded from web of National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/genome),alignment of all the coding sequences (CDSs) among five strains(American strain CO92 as reference and other four completely sequenced strains from Inner Mongolia,Jianchuan of Yunnan,Yulong of Yunnan,Naqu of Tibet in China named 91001,D182038,D106004 and Z176003 as comparison strains) was performed,and then the chromosome of Yersinia pestis was divided into several large DNA segments (named chromosomal plate in the text) according to the similarity of CDSs.Plate arrangement patterns in each strain' s chromosome and gene content of breakpoint regions were determined.Finally,genetic relationships among Yersinia pestis strains were analyzed on the basis of rearrangement diversity from paired-comparison.Results Yersinia pestis chromosomes of strains CO92,D182038,D106004,91001 were composed of 44 relatively independent plates,except strain Z176003.Gene order was very stable within each plate,while it was movable between the plates.Comparing with the reference strain CO92,13 rearrangement events occurred in the chromosomes of both strain D182038 and strain D106004,and 14 rearrangement events involved in Z176003,while 37 rearrangement events occurred in 91001.Paired-comparison data showed that only 8 plates order differences were existed between D106004 and Z176003.Forty-three breakpoint regions were identified on the chromosome of strain CO92,and 39 of them contained insertion sequences,and 25 of them were IS100.Conclusions Yersinia pestis genome represents a high degree of genetic flux,and chromosomal structures of strains are significantly different from each other.Chromosomal rearrangement events is closely related to the large number of insertion sequences in the Yersinia pestis chromosome.Rearrangement diversity among Yersinia pestis strains could reflect their genetic relationships.