Project description:Differential gene expression of Dictyostelium discoideum after infection with Legionella pneumophila was investigated using DNA microarrays. A detailed analysis of the 24 h time point post infection was performed in comparison to three controls, uninfected cells and co-incubation with Legionella hackeliae and L. pneumophila DeltadotA. One hundred and thirty-one differentially expressed D. discoideum genes were identified as common to all three experiments and are thought to be involved in the pathogenic response. Functional annotation of the differentially regulated genes revealed that apart from triggering a stress response Legionella apparently not only interferes with intracellular vesicle fusion and destination but also profoundly influences and exploits the metabolism of its host. The results provide the basis for a better understanding of the complex host-pathogen interactions and for further studies on the Dictyostelium response to Legionella infection. The bacterial strains used in this study were L. pneumophila Philadelphia I JR32, L. pneumophila Philadelphia I JR32 LELA 3118 (dotA3118:Tn903 DLL LacZ) and L. hackeliae (ATCC 35250). The Legionella strains were grown on buffered charcoal yeast extract agar (BCYE) at 37M-BM-0C with 5% CO2 atmosphere for 3 days. The D. discoideum wild-type strain AX2 was grown at 23M-BM-0C in 75 cm2 cell-culture flasks with 10 ml HL5 medium. For infection, Dictyostelium cells were harvested, resuspended in a 1:1 solution of HL5 medium and Soerensen buffer. Fifteen millilitres of a 1M-CM-^W10e6 cells/ml suspension were seeded into a 75 square-cm cell culture flask and the amoebae were inoculated with 10e7 bacteria/ml. Three different pairs of infection were compared: 1. AX2 infected with L. pneumophila JR32 versus uninfected cells; 19 microarrays of seven independent infections; 2. AX2 infected with L. pneumophila JR32 versus AX2 infected with L. pneumophila JR32 delta DotA; 4 microarrays of two independent infections; 3. AX2 infected with L. pneumophila JR32 versus AX2 infected with L. hackeliae; 4 microarrays of two independent infections. 24h post infection the RNA was isolated from 1.5M-CM-^W10e7 Dictyostelium cells and microarray analysis was performed as described (Farbrother et al., 2006).

Project description:Differential gene expression of Dictyostelium discoideum after infection with Legionella pneumophila in comparison to uninfected cells was investigated using DNA microarrays. Investigation of a 48 h time course of infection revealed several clusters of co-regulated genes, an enrichment of preferentially up- or downregulated genes in distinct functional categories and also showed that most of the transcriptional changes occurred 24 h after infection. Functional annotation of the differentially regulated genes revealed that apart from triggering a stress response Legionella apparently not only interferes with intracellular vesicle fusion and destination but also profoundly influences and exploits the metabolism of its host. For some of the identified genes, e.g. rtoA involvement in the host response has been demonstrated in a recent study, for others such a role appears plausible. The results provide the basis for a better understanding of the complex host-pathogen interactions and for further studies on the Dictyostelium response to Legionella infection. The bacterial strain used in this study was L. Pneumophila Philadelphia I JR32. The strain was grown on buffered charcoal yeast extract agar (BCYE) at 37M-BM-0C with 5% CO2 atmosphere for 3 days. The D. discoideum wild-type strain AX2 was grown at 23M-BM-0C in 75 cm2 cell-culture flasks with 10 ml HL5 medium. For infection, Dictyostelium cells were harvested, resuspended in a 1:1 solution of HL5 medium and Soerensen buffer. Fifteen millilitres of a 1M-CM-^W10e6 cells/ml suspension were seeded into a 75 cme2 cell culture flask and the amoebae were inoculated with 10e7 bacteria/ml. After different time intervals of incubation (1, 3, 6, 24, and 48 h) the RNA was isolated from 1.5M-CM-^W10e7 Dictyostelium cells. Usually two or three parallel cultures for the experiment and the control were inoculated per infection. The percentage of infected cells was determined by in situ hybridization with Legionella-specific 16S rRNA probes. The average from three independent determinations was 34, 42, 42, 57 and 82% of infected Dictyostelium cells after 1, 3, 6, 24 and 48 h, respectively.

Dataset Information

Differential expression of Dictyostelium discoideum AX2 upon infection with wt L. pneumophila JR32 vs. uninfected 24h p.i. (comparison experiment)

Publications

Dictyostelium transcriptional host cell response upon infection with Legionella.

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