Vibrio cholerae, the causative agent of cholera, is considered to be an important model organism for studying infectious diseases. However, compared to its pathogenic potential, much less is known about the bacterium’s lifestyle in its primary habitat, the aquatic environment. Such environmental habitats often contribute to pathogen emergence, which is frequently accomplished through the acquisition of novel genetic information by means of horizontal gene transfer (HGT). Natural competence for transformation as a mode of HGT plays a key role in bacterial evolution and V. cholerae enters the competence state upon growth on chitinous surfaces.
In this talk, I will show imaging- and genetics-based data that illustrate that pandemic V. cholerae strains induce two nanomachines simultaneously upon growth on chitin: the DNA-uptake complex and the type VI secretion system (T6SS). T6SS is a molecular killing device, and it fosters HGT by the deliberate killing of neighboring bacteria followed by the absorption of large stretches of preyreleased DNA. Clonal siblings are immune to T6SS attacks and therefore contribute at much lower levels to HGT events. I will also explain mechanistic aspects of the DNA uptake process, which involves a type IV pilus. This pilus is highly dynamic, as demonstrated by real-time fluorescence microscopy imaging, and significantly contributes to the colonization of chitinous surfaces under flow conditions. This imaging approach also led to the discovery that V. cholerae engages in a major pilin-specific aggregation phenotype, which is kin-specific.
I will end my presentation by speculating how this aggregation phenotype might contribute to the success of V. cholerae in nature as well as for its transmission to humans.