Identification and molecular characterization of an N-acetylmuramyl-l-alanine amidase Sle1 involved in cell separation of Staphylococcus aureus

Authors

  • Junko Kajimura,

    1. Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi Minami-ku, Hiroshima City, Hiroshima 734-8553, Japan.
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  • Tamaki Fujiwara,

    1. Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi Minami-ku, Hiroshima City, Hiroshima 734-8553, Japan.
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  • Sakuo Yamada,

    1. Department of Microbiology, Kawasaki Medical School, Matsushima 577, Kurashiki, Okayama 701-0192, Japan.
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  • Yoshika Suzawa,

    1. Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi Minami-ku, Hiroshima City, Hiroshima 734-8553, Japan.
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  • Tetsuya Nishida,

    1. Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi Minami-ku, Hiroshima City, Hiroshima 734-8553, Japan.
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  • Yoshihiro Oyamada,

    1. Microbiology Group, Pharmacology and Microbiology Research Laboratories, Dainippon Pharmaceutical, Enoki-Cho 33-94, Suita City, Osaka 564-0053, Japan.
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  • Ikue Hayashi,

    1. Research Facility, Hiroshima University Faculty of Dentistry, 1-2-3 Kasumi Minami-ku, Hiroshima City, Hiroshima 734-8553, Japan.
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  • Jun–ichi Yamagishi,

    1. Microbiology Group, Pharmacology and Microbiology Research Laboratories, Dainippon Pharmaceutical, Enoki-Cho 33-94, Suita City, Osaka 564-0053, Japan.
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  • Hitoshi Komatsuzawa,

    1. Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi Minami-ku, Hiroshima City, Hiroshima 734-8553, Japan.
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  • Motoyuki Sugai

    Corresponding author
    1. Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi Minami-ku, Hiroshima City, Hiroshima 734-8553, Japan.
      E-mail sugai@hiroshima-u.ac.jp; Tel. (+81) 82 257 5635; Fax (+81) 82 257 5639.
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E-mail sugai@hiroshima-u.ac.jp; Tel. (+81) 82 257 5635; Fax (+81) 82 257 5639.

Summary

We purified a peptidoglycan hydrolase involved in cell separation from a Staphylococcus aureus atl null mutant and identified its gene. Characterization of the gene product shows a 32 kDa N-acetylmuramyl-l-alanine amidase that we designated Sle1. Analysis of peptidoglycan digests showed Sle1 preferentially cleaved N-acetylmuramyl-l-Ala bonds in dimeric cross-bridges that interlink the two murein strands in the peptidoglycan. An insertion mutation of sle1 impaired cell separation and induced S. aureus to form clusters suggesting Sle1 is involved in cell separation of S. aureus. The Sle1 mutant revealed a significant decrease in pathogenesis using an acute infection mouse model. Atl is the major autolysin of S. aureus, which has been implicated in cell separation of S. aureus. Generation of an atl/sle1 double mutant revealed that the mutant cell separation was heavily impaired suggesting that S. aureus uses two peptidoglycan hydrolases, Atl and Sle1, for cell separation. Unlike Atl, Sle1 is not directly involved in autolysis of S. aureus.

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