Legionella-protozoa-nematode interactions in aquatic biofilms and influence of Mip on Caenorhabditis elegans colonization.
Legionella pneumophila, the causative agent of Legionnaireś disease, is naturally found in aquatic habitats. The intracellular life cycle within protozoa pre-adapted the "accidental" human pathogen to also infect human professional phagocytes like alveolar macrophages. Previous studies employing the model organism Caenorhabditis elegans suggest that also nematodes might serve as a natural host for L. pneumophila. Here, we report for the first time from a natural co-habitation of L. pneumophila and environmental nematode species within biofilms of a warm water spring. In addition, we identified the protozoan species Oxytricha bifaria, Stylonychia mytilus, Ciliophrya sp. which have never been described as potential interaction partners of L. pneumophila before. Modeling and dissection of the Legionella-protozoa-nematode interaction revealed that C. elegans ruptures Legionella-infected amoebal cells and by this means incorporate the pathogen. Further infection studies revealed that the macrophage infectivity potentiator (Mip) protein of L. pneumophila, which is known to bind collagen IV during human lung infection, promotes the colonization of the intestinal tract of L4 larvae of C. elegans and negatively influences the life span of the worms. The Mip-negative L. pneumophila mutant exhibited a 32-fold reduced colonization rate of the nematodes after 48h when compared to the wild-type strain. Taken together, these studies suggest that nematodes may serve as natural hosts for L. pneumophila, promote their persistence and dissemination in the environment, and co-evolutionarily pre-adapt the pathogen for interactions with extracellular constituents of human lung tissue.
Institut für Mikrobiologie, Technische Universität Braunschweig, Germany.
Janine
J
Rasch
Institut für Mikrobiologie, Technische Universität Braunschweig, Germany.
Stefanie
S
Krüger
UMR CARRTEL, Universite de Savoie-INRA, Le Bourget du Lac, France.
Dominique
D
Fontvieille
Institut für Mikrobiologie, Technische Universität Braunschweig, Germany.
Can M
CM
Ünal
Central Institute of the Federal Armed Forces Medical Services, Koblenz, Germany.
Rolf
R
Michel
Thermes Nationaux dAix-les Bains, Aix-les Bains, France.
Aurélie
A
Labrosse
Institut für Mikrobiologie, Technische Universität Braunschweig, Germany; Helmholtz Center for Infection Research, Braunschweig, Germany. Electronic address: m.steinert@tu-bs.de.
Michael
M
Steinert
D000818:Animals; D018441:Biofilms / Q000254:growth & development*; D016798:Ciliophora / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*; D006790:Host-Parasite Interactions; D045482:Hot Springs / Q000382:microbiology* / Q000469:parasitology*; D007875:Legionella / Q000254:growth & development / Q000502:physiology*; D056265:Microbial Interactions; D009348:Nematoda / Q000254:growth & development / Q000382:microbiology / Q000502:physiology*
Biofilms; Caenorhabditis elegans; Legionella pneumophila; Macrophage infectivity potentiator (Mip); Mematodes; Protozoa