Comparative Genomics Study Of Yersinia Pestis And Yersinia Pseudotuberculosis

Plague is a strong infectious disease that is caused by Y. pestis, and Y. pestis is also a kind of biological warfare agent. In the past, the prevalence of plague had ever brought tremendous disaster to human beings. At present, although plague is under the effective control, but WHO has considered the plague as recurrent infectious disease, and the possibility of Y. pestis used as biological warfare agent and biological terrorism is still existent. Therefore, it is significant to provide insight into the Y. pestis.Genus Yersinia consists of eleven species of Yersinia, three of which Y. pestis, Y. pseudotuberculosis and Y. enterocolitica are pathogenic for humans, and other species are non-pathogenic for humans. Y. pestis recently evolved from Y. pseudotuberculosis O:lb just 1,500-20,000 years ago. However, Y. pestis cause terrible plague, whereas Y. pseudotuberculosis merely cause gastroenteritis. Y. pestis compared with Y. pseudotuberculosis carry two additional virulence plasmids, which can explain the difference of transmission mode between both of them to some extent. However, two virulence plasmids are insufficient to explain the specific virulence of Y. pestis. The comparative genomics is a promising method to elucidate the molecular mechanism of the different phenotype between Y. pestis and Y. pseudotuberculosis. At present, the methods of comparative genomics include sequencing, DNA microarray and suppression subtractive hybridization, etc. The comparative genomics study by sequencing is undoubtedly optimal choice, but is also a laborious method. There are some genome difference between the different biovars and different isolates of bacteria. In order to find the difference among bacteria, it is impossible to determine the sequence of all isolates. At present, three strains of Y. pestis and one strain of Y. pseudotuberculosis have been sequenced, which provides a great deal of information tocompare the genome of Y. pestis with that of Y. pseudotuberculosis. Another comparative genomics method is whole genome DNA microarray, but it is also a laborious method. Suppression subtractive hybridization is a recently comparative genomics method, and can identify the difference region between the genomes of bacteria, and costs less. Therefore, the aim of this study is to screen the difference products specific to Y. pseudotuberculosis by suppression subtractive hybridization, and to print the specific fragments on a slide, and to use DNA microarray to identify typical difference fragments specific to Y. pseudotuberculosis.We found 108 DNA fragments specific to Y. pseudotuberculosis Yps33 by suppression subtractive hybridization and blast analysis. 91 DNA fragments are present in Y. pseudotuberculosis IP32953 which has been sequenced, and 17 DNA fragments is specific to K pseudotuberculosis Yps33. Six strains of Y. pseudotuberculosis and twenty-seven strains of Y. pestis were analyzed by DNA microarry, and twelve conserved DNA fragments in seven strains of Y. pseudotuberculosis, standing for 15 genes, were found. Y. pseudotuberculosis and Y. pestis have high identity, Y. pestis can be identified based on its specific genes, but these specific fragments specific to Y. pseudotuberculosis can help us to distinguish Y. pseudotuberculosis and Y. pestis correctly. In addition, these specific fragments can be used as specific marker to identify Y. pseudotuberculosis to avoid pseudopositive. It seems to be that these specific fragments have been lost in Y. pestis during the evolution of Y. pestis. This conclusion is based on 27 strains of Y. pestis and 7 strains of Y. pseudotuberculosis, so a number of strains are needed to validate this conclusion.Ninety-one fragments in Y. pseudotuberculosis Yps33 have equivalent genes in IP32953, and represent one hundred and six genes. The results show that suppression subtractive hybridization is a ideal comparative genomics method.Microarray hybridization results show that all 108 fragments are present in Yps33 and Yps28 which belong to serotype I, and other four strains of Y. pseudotuberculosis lost some fragments to some extent. Serotype I Y. pseudotuberculosis carry nine specific fragments compared with other serotypes. The results indicate that there are some...