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The Legionella pneumophila response regulator LqsR promotes host cell interactions as an element of the virulence regulatory network controlled by RpoS and LetA.
- Source :
-
Cellular microbiology [Cell Microbiol] 2007 Dec; Vol. 9 (12), pp. 2903-20. Date of Electronic Publication: 2007 Jul 05. - Publication Year :
- 2007
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Abstract
- Legionella pneumophila is an opportunistic human pathogen that replicates within environmental amoebae including Acanthamoeba castellanii and Dictyostelium discoideum. The Icm/Dot type IV secretion system promotes phagocytosis and intracellular replication of L. pneumophila in an endoplasmic reticulum-derived 'Legionella-containing vacuole' (LCV). L. pneumophila adopts a biphasic life cycle consisting of a replicative growth phase and a transmissive (stationary) phase, the latter of which is characterized by the preferential expression of genes required for motility and virulence. A bioinformatic analysis of the L. pneumophila genome revealed a gene cluster homologous to the Vibrio cholerae cqsAS genes, encoding a putative quorum sensing autoinducer synthase (lqsA) and a sensor kinase (lqsS), which flank a novel response regulator (lqsR). We report here that an L. pneumophila lqsR deletion mutant grew in broth with the same rate as wild-type bacteria, but entered the replicative growth phase earlier. Overexpression of lqsR led to an elongated morphology of the bacteria. The lqsR mutant strain was found to be more salt-resistant and impaired for intracellular growth in A. castellanii, D. discoideum and macrophages, formation of the ER-derived LCV and toxicity. Moreover, L. pneumophila lacking LqsR, as well as strains lacking the stationary sigma factor RpoS or the two-component response regulator LetA, were phagocytosed less efficiently by A. castellanii, D. discoideum or macrophages. The expression of lqsR was dependent on RpoS and, to a lesser extent, also on LetA. DNA microarray experiments revealed that lqsR regulates the expression of genes involved in virulence, motility and cell division, consistent with a role for LqsR in the transition from the replicative to the transmissive (virulent) phase. Our findings indicate that LqsR is a novel pleiotropic regulator involved in RpoS- and LetA-controlled interactions of L. pneumophila with phagocytes.
- Subjects :
- Acanthamoeba castellanii microbiology
Animals
Cell Division genetics
Cell Line
Dictyostelium microbiology
Gene Deletion
Gene Dosage
Gene Expression Profiling
Gene Expression Regulation, Bacterial
Humans
Legionella pneumophila cytology
Legionella pneumophila genetics
Locomotion genetics
Macrophages microbiology
Oligonucleotide Array Sequence Analysis
Transcription Factors genetics
Virulence
Bacterial Proteins physiology
Legionella pneumophila growth & development
Sigma Factor physiology
Transcription Factors physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1462-5814
- Volume :
- 9
- Issue :
- 12
- Database :
- MEDLINE
- Journal :
- Cellular microbiology
- Publication Type :
- Academic Journal
- Accession number :
- 17614967
- Full Text :
- https://doi.org/10.1111/j.1462-5822.2007.01005.x