Legionella dumoffii DjlA, a member of the DnaJ family, is required for intracellular growth.
Legionella dumoffii is one of the common causes of Legionnaires' disease and is capable of replicating in macrophages. To understand the mechanism of survival within macrophages, transposon mutagenesis was employed to isolate the genes necessary for intracellular growth. We identified four defective mutants after screening 790 transposon insertion mutants. Two transposon insertions were in genes homologous to icmB or dotC, within dot/icm loci, required for intracellular multiplication of L. pneumophila. The third was in a gene whose product is homologous to the 17-kDa antigen forming part of the VirB/VirD4 type IV secretion system of Bartonella henselae. The fourth was in the djlA (for "dnaj-like A") gene. DjlA is a member of the DnaJ/Hsp40 family. Transcomplementation of the djlA mutant restored the parental phenotype in J774 macrophages, A549 human alveolar epithelial cells, and the amoeba Acanthamoeba culbertsoni. Using confocal laser-scanning microscopy and transmission electron microscopy, we revealed that in contrast to the wild-type strain, L. dumoffii djlA mutant-containing phagosomes were unable to inhibit phagosome-lysosome fusion. Transmission electron microscopy also showed that in contrast to the virulent parental strain, the djlA mutant was not able to recruit host cell rough endoplasmic reticulum. Furthermore, the stationary-phase L. dumoffii djlA mutants were more susceptible to H2O2, high osmolarity, high temperature, and low pH than was their parental strain. These results indicate that DjlA is required for intracellular growth and organelle trafficking, as well as bacterial resistance to environmental stress. This is the first report demonstrating that a single DjlA-deficient mutant exhibits a distinct phenotype.
Ohnishi
Hiroko
H
Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Mizunoe
Yoshimitsu
Y
Takade
Akemi
A
Tanaka
Yoshitaka
Y
Miyamoto
Hiroshi
H
Harada
Mine
M
Yoshida
Shin-ichi
S
D000048:Acanthamoeba / Q000382:microbiology; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004251:DNA Transposable Elements; D004847:Epithelial Cells / Q000382:microbiology*; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018869:Heat-Shock Response; D006801:Humans; D007875:Legionella / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D008247:Lysosomes / Q000502:physiology; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D016254:Mutagenesis, Insertional; D010588:Phagosomes / Q000382:microbiology / Q000502:physiology
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; C494647:DNAJB1 protein, human; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins