Identification and characterization of a chromosomal virulence gene, vacJ, required for intercellular spreading of Shigella flexneri

Authors

  • T. Suzuki,

    1. Department of Bacteriology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan.
    Search for more papers by this author
  • T. Murai,

    1. Central Laboratory of Medical Science, Division of Electron Microscopy, School of Medicine, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113, Japan.
    Search for more papers by this author
  • I. Fukuda,

    1. Department of Bacteriology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan.
    Search for more papers by this author
  • T. Tobe,

    1. Department of Bacteriology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan.
    Search for more papers by this author
  • M. Yoshikawa,

    1. Department of Bacteriology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan.
    Search for more papers by this author
  • C. Sasakawa

    Corresponding author
    1. Department of Bacteriology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108, Japan.
    • * For correspondence. Tel.(3)3443 8111; Fax (3)3443 3893.

    Search for more papers by this author

Summary

Intercellular spreading of shigellae Is a prerequisite for shigellosis, although the molecular mechanisms underlying the phenomenon are still largely obscure. To elucidate some of these mechanisms, we performed random TniO insertion mutagenesis in Shigella flexneri YSH6000T and found a chromosomal locus in the Notl-J segment responsible for bacterial spreading. The locus affected in the mutant, designated vacJ, was neither involved in the invasion of epithelial cells nor in intracellular movement, but was required for intercellular spread. The vacJ mutant was capable of forming bacterium-containing membranous protrusions within the infected cell, but had diminished ability to move from the protrusions into the cytoplasm of the adjacent epithelial cells. Cloning and sequencing of the vacJ region Indicated that the vacJ gene encoded a 28.0 kDa protein possessing a signal peptide at the N-terminus, which contained the motif characteristic of lipoproteins. The analysis of the vacJ product indicated that VacJ was exposed on the bacterial surface. The vacJ gene was distributed among shigellae and enteroinvasive Escherichia coli, and the constructed vacJ mutants failed to spread intercellularly, indicating that vacJ is a chromosomal gene essential for the pathogenicity of shigeiiae.

Ancillary