Legionella pneumophila mip gene potentiates intracellular infection of protozoa and human macrophages

Nicholas P. Cianciotto*, Barry S. Fields

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

235 Scopus citations


Legionella pneumophila is an intracellular parasite of freshwater protozoa and human macrophages. Recent studies determined that the macrophage infectivity potentiator (Mip) surface protein, a prokaryotic homolog of the FK506-binding proteins, is required for optimal infection of macrophages. To determine whether Mip is also involved in L. pneumophila infection of protozoa, we examined the ability of a strain lacking Mip to parasitize Hartmannetta amoebae and Tetrahymena ciliates. After 3 days of incubation, ≈1000-fold fewer bacteria were recovered from protozoan cocultures infected with the Mip- strain than from those cocultures infected with an isogenic Mip+ strain. The mip mutant was, however, not impaired in its ability to bind to amoebae cell surfaces, indicating that Mip is involved in bacterial resistance to intracellular killing and/or intracellular multiplication. These data suggest that L. pneumophila employs similar genes and mechanisms to infect human cells and protozoa. Furthermore, they support the hypothesis that the ability of L. pneumophila to parasitize macrophages and hence to cause human disease is a consequence of its prior adaptation to intracellular growth within protozoa.

Original languageEnglish (US)
Pages (from-to)5188-5191
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number11
StatePublished - 1992


  • Evolution
  • FK506-binding proteins
  • Hartmannella
  • Intracellular parasitism
  • Tetrahymena

ASJC Scopus subject areas

  • General


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