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Association of flagellum expression and intracellular growth of Legionella pneumophila

J M Pruckler1, R F Benson, M Moyenuddin

  • 1Division of Bacterial and Mycotic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.

Infection and Immunity
|December 1, 1995
PubMed

Insights

Legionella pneumophila flagellar expression is crucial for infecting amoebae and human cells. While not essential for virulence, flagella significantly impact bacterial infectivity and multiplication in host cells.

Area of Science:

  • Microbiology
  • Cell Biology
  • Infectious Diseases

Background:

  • Legionella pneumophila is an opportunistic pathogen that infects amoebae and human phagocytic cells.
  • The role of bacterial flagella in host cell infection is a key area of research.

Purpose of the Study:

  • To investigate the function of Legionella pneumophila flagella in the infection of amoebae (Hartmannella vermiformis) and human monocyte-like cells (U937).
  • To determine if flagellar expression is essential for bacterial virulence and infectivity.

Main Methods:

  • Construction of insertional mutants using mini-Tn10 transposon.
  • Identification of flagellar-deficient (F-) and flagellar-positive (F+) mutants based on reactivity with antiflagellar antisera.
  • Characterization of the infectivity and intracellular multiplication of 20 mutants in H. vermiformis and U937 cells.

Main Results:

  • Seven out of ten F- mutants showed attenuated multiplication in amoebae and failed to multiply in U937 cells.
  • Three F- mutants exhibited wild-type-like multiplication in amoebae and limited multiplication in U937 cells.
  • All ten F+ mutants displayed infectivity comparable to the wild-type strain in both cell types.

Conclusions:

  • Flagellar expression, rather than the flagellar structure itself, is linked to the ability of Legionella pneumophila to infect amoebae and human phagocytic cells.
  • Mutations in genes critical for flagellum expression also impair the infection process, suggesting a dual role in virulence.

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