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Open Access Research article

Genetic diversity among major endemic strains of Leptospira interrogans in China

Ping He1, Yue-Ying Sheng1, Yao-Zhou Shi2, Xiu-Gao Jiang3, Jin-Hong Qin1, Zhi-Ming Zhang2, Guo-Ping Zhao24* and Xiao-Kui Guo1*

Author Affiliations

1 Department of Microbiology and Parasitology, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China

2 National Engineering Center for Biochip at Shanghai, Zhangjiang High Tech Park, Shanghai 201203, China

3 National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention (ICDC, CCDC), Beijing 102206, China

4 State Key Laboratory for Disease and Health Genomics, Chinese National Human Genome Center at Shanghai, Zhangjiang High Tech Park, Shanghai 201203, China

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BMC Genomics 2007, 8:204  doi:10.1186/1471-2164-8-204

Published: 1 July 2007

Abstract

Background

Leptospirosis is a world-widely distributed zoonosis. Humans become infected via exposure to pathogenic Leptospira spp. from contaminated water or soil. The availability of genomic sequences of Leptospira interrogans serovar Lai and serovar Copenhageni opened up opportunities to identify genetic diversity among different pathogenic strains of L. interrogans representing various kinds of serotypes (serogroups and serovars).

Results

Comparative genomic hybridization (CGH) analysis was used to compare the gene content of L. interrogans serovar Lai strain Lai with that of other 10 L. interrogans strains prevailed in China and one identified from Brazil using a microarray spotted with 3,528 protein coding sequences (CDSs) of strain Lai. The cutoff ratio of sample/reference (S/R) hybridization for detecting the absence of genes from one tested strain was set by comparing the ratio of S/R hybridization and the in silico sequence similarities of strain Lai and serovar Copenhageni strain Fiocruz L1-130. Among the 11 strains tested, 275 CDSs were found absent from at least one strain. The common backbone of the L. interrogans genome was estimated to contain about 2,917 CDSs. The genes encoding fundamental cellular functions such as translation, energy production and conversion were conserved. While strain-specific genes include those that encode proteins related to either cell surface structures or carbohydrate transport and metabolism. We also found two genomic islands (GIs) in strain Lai containing genes divergently absent in other strains. Because genes encoding proteins with potential pathogenic functions are located within GIs, these elements might contribute to the variations in disease manifestation. Differences in genes involved in O-antigen biosynthesis were also identified for strains belonging to different serogroups, which offers an opportunity for future development of genomic typing tools for serological classification.

Conclusion

CGH analyses for pathogenic leptospiral strains prevailed in China against the L. interrogans serovar Lai strain Lai CDS-spotted microarrays revealed 2,917 common backbone CDSs and strain specific genes encoding proteins mainly related to cell surface structures and carbohydrated transport/metabolism. Of the 275 CDSs considered absent from at least one of the L. interrogans strains tested, most of them were clustered in the rfb gene cluster and two putative genomic islands (GI A and B) in strain Lai. The strain-specific genes detected via this work will provide a knowledge base for further investigating the pathogenesis of L interrogans and/or for the development of effective vaccines and/or diagnostic tools.