Cloning and characterization of the gene encoding the z66 antigen of Salmonella enterica serovar Typhi

Authors

  • Xinxiang Huang,

    1. Department of Microbiology and Bioinformatics, Regeneration and Advanced Medical Science, Gifu University School of Medicine, 40 Tsukasa Machi, Gifu 500-8750, Japan
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  • Le V. Phung,

    1. Department of Microbiology, Hanoi Medical School, Ton Sthat Tung Str, Dongda, Hanoi, Viet Nam
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  • Surang Dejsirilert,

    1. Department of Medical Sciences, National Institute of Health, Tiwanond Road, Nonthaburi 11000, Thailand
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  • Prapawadee Tishyadhigama,

    1. Department of Medical Sciences, National Institute of Health, Tiwanond Road, Nonthaburi 11000, Thailand
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  • Ying Li,

    1. Department of Microbiology and Bioinformatics, Regeneration and Advanced Medical Science, Gifu University School of Medicine, 40 Tsukasa Machi, Gifu 500-8750, Japan
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  • Hongshen Liu,

    1. Department of Microbiology and Bioinformatics, Regeneration and Advanced Medical Science, Gifu University School of Medicine, 40 Tsukasa Machi, Gifu 500-8750, Japan
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  • Kenji Hirose,

    1. Department of Bacteriology, National Institute of Infectious Disease, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
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  • Yoshiaki Kawamura,

    1. Department of Microbiology and Bioinformatics, Regeneration and Advanced Medical Science, Gifu University School of Medicine, 40 Tsukasa Machi, Gifu 500-8750, Japan
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  • Takayuki Ezaki

    Corresponding author
    1. Department of Microbiology and Bioinformatics, Regeneration and Advanced Medical Science, Gifu University School of Medicine, 40 Tsukasa Machi, Gifu 500-8750, Japan
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Corresponding author. Tel.: +81-58-26-72-239; fax: +81-58-26-70-156, E-mail address: tezaki@cc.gifu-u.ac.jp

Abstract

Z66 antigen-positive strains of Salmonella enterica serovar Typhi change flagellin expression in only one direction from the z66 antigen to the d or j antigen, which is different from the phase variation of S. enterica serovar Typhimurium. In the present study, we identified a new flagellin gene in z66 antigen-positive strains of S. enterica serovar Typhi. The genomic structure of the region containing this new flagellin gene was similar to that of fljBA operon of biphasic S. enterica serovars. A fljA-like gene was present downstream of the new flagellin gene. A rho-independent terminator was located between the new flagellin gene and the fljA-like gene. Hin-like gene was not present upstream of the new flagellin gene. We generated a mutant strain of S. enterica serovar Typhi, which carries a deletion of the new flagellin gene. Western blotting revealed that the 51-kDa z66 antigen protein was absent from the population of proteins secreted by the mutant strain. Southern hybridization demonstrated that the z66 antigen-positive strains of S. enterica serovar Typhi carried the new flagellin gene and fliC on two different genomic EcoRI fragments. When z66 antigen-positive strains were incubated with anti-z66 antiserum, the flagellin expression by S. enterica serovar Typhi changed from z66 antigen to j antigen. The new flagellin gene and the fljA-like gene were absent in the strain with altered flagellin expression. These results suggested that the new flagellin gene is a fljB-like gene, which encodes the z66 antigen of S. enterica serovar Typhi, and that deletion of fljBA-like operon may explain why S. enterica serovar Typhi alters the flagellin expression in only one direction from the z66 antigen to the d or j antigen.

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