Charles Van der Henst
Swiss Federal Institute of Technology Laussane, Switzerland
Title: The interplay between the amoeba Acanthamoeba castellanii and the human pathogen Vibrio cholerae
Biography
Biography: Charles Van der Henst
Abstract
Vibrio cholerae is a Gram-negative bacterial pathogen, which is responsible for the severe diarrheal disease cholera. The occurrence of the bacterium in the aquatic environment represents a key epidemiological aspect of the disease as it increases the risks of cholera outbreaks. The current view about facultative bacterial pathogens suggests that virulence determinants evolved in the natural environment where they provide a fitness advantage. To better understand and potentially even predict cholera outbreaks, it is of prime importance to decipher the environmental life style of V. cholerae. Among eukaryotic predators, protists such as amoebae play major roles with respect to the regulation of bacterial populations. The amoeba Acanthamoeba castellanii represents an interesting model for the interplay with V. cholerae since both organisms occur in the same environmental niches. A. castellanii shows a biphasic life cycle between a metabolically active/feeding form (trophozoite) and a stress-induced dormant/resistant form (cyst). In this study, we tested the ability of V. cholerae to survive the predation exerted by A. castellanii and to use the amoeba as a host for intracellular proliferation. We monitored the A. castellanii-colonizing bacteria in real time using live-cell confocal microscopy. We observed that V. cholerae shows different survival strategies that are specific for either the trophozoite or the cyst stage. Based on our observations we proposed a model of the complex life cycle between V. cholerae and A. castellanii. Next, we tested diverse mutant strains in this host-pathogen interaction model and observed impairment at different steps of the V. cholerae life cycle. The data provided in this study redefines V. cholerae as a facultative intracellular pathogen. Moreover, the ability of V. cholerae to use a natural bacterial predator as a host might contribute to its environmental fitness and the maintenance of virulence determinants.