The Study On The Coding Sequence Of Yersinia Pestis And Pathogenic Genes Of Microtus Yersinia Pestis

Plague as a natural focus infection disease has ravaged human populations in three major pandemic waves, which have claimed hundreds of thousands of lives. There are twelve plague focus and eighteen ecological types in China. However, two special types of Yersinia pestis were found in our country, which have strong virulence to small animals as Mus musculus albus and have little virulence to large animals such as cony pig and rabbit. And in the epidemic focus it havn't been found the patient who infected Microtus Yersinia pestis.A pneumonic plague occurrenced in Yulong in 2005, which caused five patient and two dead of it. After the epidemiological investigation, Yersinia pestis was isolated from the rodents in the locality. Now in order to comprehend the new plague foci we sequenced the Yersinia pestis which were separated from the new foci and the neighborhood foci.After the analynis of the genome sequences of Yersinia pestis from different areas in the world, we had the homologisation relationship of coding sequence in comparing any two strains. On this basis, Yulong strain compared with control of plague bacteria in CDS, insertion sequences and genomic rearrangements. From the result of it, we found the Yulong strain and Tibet strain have the most similar strain relationship, CDS homology highest and rearrangement fragment least.As the differences in biochemical properties among the three genomes, we compare maltose-related genes in the whole genome sequences and find some genes mutated. After we have done experiments in seventy-two of Yersinia pestis in China, we found malt and malZ exist frameshift in the two genes.According to the comparison of the CDS, we have obtained 21 specific genes for the Microtus Yersinia pestis(91001) by screening in unique type of filter-related genes. Their COG functional classification showed that 7 genes associated with metabolism, five genes associated with cell signal transduction, and 7 genes can't found in the COG classification.Primers were designed in this 21-bit point mutation, and we validate the mutation in 131 strains which isolated in two types of Microtus foci and other focis in China, then we compare the actual distribution and changes of these genes in circumstances.The experimental results show that 1) 3 genes (T2, T18, T24 all gene mutation) haven't mutated in the Microtus Yersinia pestis. 2) a point mutation of T13 genes, some of Yersinia pestis isolated from Microtus Brandt are not mutant strains. 3) 2 genes (T30 point mutation, Q5 gene deletion) have different styles in the control strains.4) In these 21 genes, 3 genes (S1, T29 gene point mutation, T3 gene deletion) have mutatedn in the Brandt Microtus Yersinia pestis but not mutated in the Qinghai Microtus Yersinia pestis. These genes can be used in typing the two Microtus Yersinia pestis and can be used in the epidemiology for significance of traceability.5) There are 12 genes (9 point mutations, three gene deletion) have the true sense of the mutation in the two Microtus Yersinia pestis. And these 12 genes may be caused special virulence in Microtus Yersinia pestis. Among them, two genes belong to information storage-processing-related genes in COG functional classification, their expressions are the gene deletion mutation and the genes are in the type of rapid variation. One of them annotated for the DEAD-box protein family helicase, the other one annotated for the AraC protein family of transcription regulatory proteins, and both of them are related to the pathogenicity of bacteria, we will have the study on the function of these genes in the next step.The study also found that China's Microtus Yersinia pestis have obvious mutation as missing the 510bp fragment in T6 gene. In order to know the actual impact of the gene T6 in the Microtus Yersinia pestis, We have the study by using one-step inactivation method in Yersinia pestis.