Differences in protein synthesis between wild type and intracellular growth-deficient strains of Legionella pneumophila in U937 and Acanthamoeba polyphaga.
An important aspect of Legionnaires' disease is the growth of the causative agent, Legionella pneumophila, within infected host cells. Many proteins including stress proteins of L. pneumophila were strongly induced in a wild type strain that had been used to infect U937 human macrophage-like cells. In contrast, the expression of the proteins was much weaker within a protozoan host, Acanthamoeba polyphaga. The results suggested that active bacterial protein synthesis is required more within macrophages than within protozoa for adaptation of L. pneumophila to intracellular environments. The synthesis of these proteins was not observed in intracellular growth-deficient strains after infection in either type of host cells. The inability of protein synthesis in these strains is correlated with their inability of intracellular growth. Furthermore, on U937 infection, the synthesis of beta-galactosidase encoded in an inducible reporter construct immediately ceased in the in intracellular growth-deficient strains after infection, while the wild type strain was able to synthesize it during the course of infection. These results suggested that the intracellular growth of Legionella pneumophila within macrophages requires active protein synthesis from an earlier stage of bacterial infection.
Department of Microbiology and COE Program in the 21st Century, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka-shi, Shizuoka 422-8526, Japan. miyakem@ys7.u-shizuoka-ken.ac.jp
Masaki
M
Miyake
Takashi
T
Fukui
Yasuyuki
Y
Imai
D000048:Acanthamoeba / Q000382:microbiology*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D006801:Humans; D016952:Legionella pneumophila / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000472:pathogenicity*; D008264:Macrophages / Q000382:microbiology*; D009154:Mutation; D010587:Phagocytosis; D020298:U937 Cells / Q000382:microbiology
D001426:Bacterial Proteins; D006360:Heat-Shock Proteins