Role for the Ankyrin eukaryotic-like genes of Legionella pneumophila in parasitism of protozoan hosts and human macrophages

Legionella pneumophila is a ubiquitous organism in the aquatic environment where it is capable of invasion and intracellular proliferation within various protozoan species and is also capable of causing pneumonia in humans. In silico analysis showed that the three sequenced L. pneumophila genomes ea...

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Bibliographic Details
Published in:Environmental microbiology 2008-06, Vol.10 (6), p.1460-1474
Main Authors: Habyarimana, Fabien, Al-khodor, Souhaila, Kalia, Awdhesh, Graham, James E, Price, Christopher T, Garcia, Maria Teresa, Kwaik, Yousef Abu
Format: Article
Language:English
Subjects:
Animals
Ankyrins - genetics
Ankyrins - physiology
Bacterial Proteins - genetics
Bacterial Proteins - physiology
Cell Line
Cells, Cultured
Colony Count, Microbial
Eukaryota - microbiology
Gene Deletion
Gene Expression Profiling
Gene Expression Regulation, Bacterial
Gene Order
Genes, Bacterial
Humans
Legionella pneumophila - genetics
Legionella pneumophila - growth & development
Legionella pneumophila - pathogenicity
Macrophages - microbiology
Repetitive Sequences, Amino Acid
Sigma Factor - physiology
Virulence
Virulence Factors - genetics
Virulence Factors - physiology
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Summary:Legionella pneumophila is a ubiquitous organism in the aquatic environment where it is capable of invasion and intracellular proliferation within various protozoan species and is also capable of causing pneumonia in humans. In silico analysis showed that the three sequenced L. pneumophila genomes each contained a common multigene family of 11 ankyrin (ank) genes encoding proteins with ~30-35 amino acid tandem Ankyrin repeats that are involved in protein-protein interactions in eukaryotic cells. To examine whether the ank genes are involved in tropism of protozoan hosts, we have constructed isogenic mutants of L. pneumophila in ten of the ank genes. Among the mutants, the ΔankH and ΔankJ mutants exhibit significant defects in robust intracellular replication within A. polyphaga, Hartmanella vermiformis and Tetrahymena pyriformis. A similar defect is also exhibited in human macrophages. Most of the ank genes are upregulated by L. pneumophila upon growth transition into the post-exponential phase in vitro and within Acanthamoeba polyphaga, and this upregulation is mediated, at least in part, by RpoS. Single-cell analyses have shown that upon co-infection of the wild-type strain with the ankH or ankJ mutant, the replication defect of the mutant is rescued within communal phagosomes harbouring the wild-type strain, similar to dot/icm mutants. Therefore, at least two of the L. pneumophila eukaryotic-like Ank proteins play a role in intracellular replication of L. pneumophila within amoeba, ciliated protozoa and human macrophages. The Ank proteins may not be involved in host tropism in the aquatic environment. Many of the L. pneumophila eukaryotic-like ank genes are triggered upon growth transition into post-exponential phase in vitro as well as within A. polyphaga. Our data suggest a role for AnkH and AnkJ in modulation of phagosome biogenesis by L. pneumophila independent of evasion of lysosomal fusion and recruitment of the rough endoplasmic reticulum.
ISSN:1462-2912
1462-2920
DOI:10.1111/j.1462-2920.2007.01560.x