Research Project Personnic

Phenotypic heterogeneity of Legionella


Considering clonal bacterial populations as ensembles of identical individuals is biologically unrealistic, as non-genetic sources of phenotypic variation contribute to marked cell-to-cell differences within isogenic populations. Phenotypic noise (stochasticity) and bacterial cell context (determinism) are prime sources for variations in phenotypic traits among clonal bacteria.

Microbial cell individuality is an important topic to advance our understanding of the interaction of an organism with its environment. In this frame, the opportunistic human pathogen Legionella pneumophila, with its elaborated life cycle, is an excellent model organism. This ubiquitous environmental bacterium resides within biofilms and replicates within both the genetically tractable social protozoa Dictyostelium discoideum and the pathogenic amoeba Acanthamoeba castellanii. L. pneumophila colonizes our artificial water supply chains and upon inhalation of contaminated aerosols, the pathogen invades the lung alveolar macrophages where it replicates and causes a severe pneumonia termed Legionnaires’ disease.

Our research is embedded in ongoing research activities of the group led by Prof. Hubert Hilbi. We work at the single cell/subset level as it provides insight that cannot be obtained using the population level average analysis. We aim to investigate at benefits of phenotypic variations along bacterial life cycle and in fluctuating environments as well as to delineate the pathways governing heterogeneity. Identification of subpopulation specific biomarkers may ultimately shed light on new therapeutic targets and provide valuable insights to reduce environmental dissemination of Legionella pneumophila.


Our work relies on various techniques including fluorescent reporters design, classical microbiology, cell biology and infection assays, chemostats, confocal microscopy, real-time microscopy, FACS, sorting, proteomics.