Genetyping And Adaptive Microevolutionary Analysis Of Yersinia Pestis

Aim: The principal molecular strategies for bacterial microevolution include mutation, rearrangement and lateral gene transfer. Based on this fact, we systematically studied genomic diversities caused by these three evolutionary tactics of Y. pestis in order to provide fundamental data for revealing microevolution of Y. pestis during expansion of natural plague foci and develop a genotying system for Chinese Y. pestis.Methods: In order to find biovar Antiqua-specific sequences, suppression subtractive hybridization (SSH) was performed between the Antiqua strain and strains of other biovars; The genome sequences of Y. pestis CO92, KIM, 91001 and Y. pseudotuberculosis IP32953 were retrieved from GenBank for comparing IS-mediated rearrangement. Forty IS loci were selected for investigating IS-mediated rearrangement profiles among Y. pestis strains isolated from different plague loci in China. Two pairs of primers, one (F-L/F-R) specific to flanking regions and another (IS-c-L/IS-c-R) specific to two termini of IS element, were designed in order to analyze the topology of each IS location in 260 strains of Y. pestis and 7 strains of Y. pseudotuberculosis.Results: (1) Only a 383bp fragment, specific to the strains of Y. pestis (biovar Antiqua) from Marmota baibacina-Spermophilus undulates Plague Focus of the Tianshan Mountains was found by SSH. The 383bp fragment is a new kind of different regions (DFRs). (2) On the basis of rearrangement profiles of 40 loci in 260 strains of Y. pestis, 33 genotypes were identified. Among them, 13 genotypes were dominating, including 89.2% (232/260) of strains analyzed. It was found that the thirteen genotypes correlated well with the plague foci and biovars. (3) According to DFR profiles, pseudogene profiles and rearrangement profiles of 260 strains of Y. pestis isolated from China, a genotying system for Chinese Y. pestis was developed. (4) Fifty-nine genomovars were identified in 902 strains of Y. pestis isolated from China by using this genotying system. Conclusion: It is further demonstrated that Y. pestis was evolved from Y. pseudotuberculosis and Y. pestis strains from Marmota baibacina-Spermophilus undulates Plague Focus of the Tianshan Mountains may be ancient and one of the origins of plague transmission in China. As an ancient and special lineage, Y. pestis strains of biovar Microtus have unique virulence and transmission features. The genotying system for Chinese Y. pestis is simple and reliable. It can separate strains of Y. pestis isolated from different plague foci in China. We firstly propose the concept of primary genomovars and subordinary genomovars. Only the primary ones play key roles in microevolution of Y. pestis during expansion of plague foci in China, and hence the possible adaptive microevolution of Y. pestis in China is proposed based on our genotying analysis.