Project description:Legionella pneumophila are important opportunistic pathogens for which environmental reservoirs such as protists are crucial for the infection of humans. Free-living amoebae are considered key hosts providing nutrients and shelter for highly efficient intracellular proliferation of L. pneumophila, which eventually leads to lysis of the amoeba host cell. Yet, the significance of other bacterial players for L. pneumophila ecology is poorly understood. In this study we used a ubiquitous amoeba and their bacterial endosymbiont to investigate the impact of this common association on L. pneumophila infection. We demonstrate that Acanthamoeba castellanii harboring the chlamydial symbiont Protochlamydia amoebophila were able to erase L. pneumophila and, in contrast to symbiont-free amoebae, survived the infection and were able to resume growth. Environmental amoeba isolates harboring P. amoebophila were equally well-protected, and fresh environmental isolates of L. pneumophila were equally well-erased, suggesting ecological relevance of this symbiont-mediated protection. We further show that protection was not mediated by impaired L. pneumophila uptake. Instead, we observed reduced virulence of L. pneumophila released from symbiont-containing amoebae that is strongly supported by transcriptome data. Interference with transition to the transmissive phase is thus likely the basis for this protection. Finally, our data indicate that the defensive response of amoebae harboring P. amoebophila leaves the amoebae with superior fitness reminiscent of immunological memory. Given that mutualistic associations between bacteria and amoebae are widely distributed, P. amoebophila and potentially other amoeba endosymbionts could be key elements in shaping environmental survival, abundance and virulence of this important pathogen thereby affecting frequency of human infection.
Project description:Legionella pneumophila is a Gram-negative facultative intracellular human pathogen with a distinct biphasic lifestyle. One of its primary environmental hosts in the free-living amoeba Acanthamoeba castellanii and its infection by L. pneumophila mimics that seen in human macrophages. Here we present analysis of strand specific sequencing of the transcriptional response of L. pneumophila in broth growth and in infection of A. castellanii.
Project description:Legionella pneumophila is a Gram-negative facultative intracellular human pathogen with a distinct biphasic lifestyle. One of its primary environmental hosts in the free-living amoeba Acanthamoeba castellanii and its infection by L. pneumophila mimics that seen in human macrophages. Here we present analysis of strand specific sequencing of the transcriptional response of L. pneumophila in broth growth and in infection of A. castellanii. Examination of 2 infection and 3 broth growth time points
Project description:This SuperSeries is composed of the following subset Series: GSE26473: Secreted bacterial effectors that inhibit host protein synthesis are critical for induction of the innate immune response to virulent Legionella pneumophila [exp1] GSE26490: Secreted bacterial effectors that inhibit host protein synthesis are critical for induction of the innate immune response to virulent Legionella pneumophila [exp2] Refer to individual Series
Project description:Legionnaire’s Disease is a growing concern for the United States and Europe, with disease incidences rising 6-fold since 2002. These recorded cases are increasingly associated with antibiotic resistant Legionella pneumophila, the causative agent of Legionnaire’s Disease and overall Legionellosis. With this, the need to study L. pneumophilainfections has never been greater. Current methodology for Legionella pneumophila infection studies often revolves around either artificial administration using intranasal or intratracheal delivery, semi-authentic delivery using bioaerosols and individual delivery systems (i.e. nose cones), or the burgeoning field of authentic exposure scenarios using aerosol generating showerhead devices. Here, we developed an alternative method using a Madison Aerosol Chamber as a means of generating and delivering bioaerosols in mice. We show that bioaerosol delivery using the Aerosol Exposure Chamber is very effective at exposing mice to various doses of L. pneumophila. RNASeq analyses revealed a robust immune response to bioaerosol delivered L. pneumophila comprising of activations of classical markers of infection and inflammation, including Cxcl and Ccl family genes and Il-1β. Similar gene expression profiles were observed when animals were intranasally exposed to L. pneumophila. Intranasal delivery resulted in a shorter duration of activation of several genes, indicating a lack of realistic infection response. Taken together, this evidence shows that our system delivers similar, if not better, results than intranasal inoculation while allowing researchers to study bioaerosol generation and delivery mechanisms simultaneously, critical factors for studying Legionella pneumophila infection. Such a new approach will allow for more accurate investigations to understand the effects of inhaling to Legionella contaminated drinking water.
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.
