The Legionella pneumophila LidA protein: a translocated substrate of the Dot/Icm system associated with maintenance of bacterial integrity

Authors

  • Gloria M. Conover,

    1. Department of Molecular Biology and Microbiology and
    Search for more papers by this author
  • Isabelle Derré,

    1. Department of Molecular Biology and Microbiology and
    Search for more papers by this author
  • Joseph P. Vogel,

    1. Department of Molecular Biology and Microbiology and
    2. Howard Hughes Medical Institute, Tufts University School of Medicine,136 Harrison Ave M and V 409, Boston, MA, 02111, USA.
    Search for more papers by this author
    • Present address: Department of Molecular Microbiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO, 63110, USA.

  • Ralph R. Isberg

    Corresponding author
    1. Department of Molecular Biology and Microbiology and
    2. Howard Hughes Medical Institute, Tufts University School of Medicine,136 Harrison Ave M and V 409, Boston, MA, 02111, USA.
    Search for more papers by this author

Summary

Legionella pneumophila establishes a replication vacuole within phagocytes that requires the bacterial Dot/Icm apparatus for its formation. This apparatus is predicted to translocate effectors into host cells. We hypothesized that some translocated proteins also function to maintain the integrity of the Dot/Icm translocator. Mutations that destroy this function are predicted to result in a Dot/Icm complex that poisons the bacterium, resulting in reduced viability. To identify such mutants, strains were isolated (called lid ) that showed reduced viability on bacteriological medium in the presence of an intact Dot/Icm apparatus, but which had high viability in the absence of the translocator. Several such mutants were analysed in detail to identify candidate strains that may have lost the ability to synthesize a translocated substrate of Dot/Icm. Two such strains had mutations in the lidA gene. The LidA protein exhibits properties expected for a translocated substrate of Dot/Icm that is important for maintenance of bacterial cell integrity: it associates with the phagosomal surface, promotes replication vacuole formation, and is important for both efficient intracellular growth and high viability on bacteriological media after introduction of a plasmid that allows high level expression of the dotA gene.

Ancillary