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Abstract
The worst epidemic of cholera in recent history between 2010 and 2013 in Haiti caused the
death of more than 8,000 Haitians. While Vibrio cholera is mainly considered as the
responsible pathogenic agent, the actual pathogen is a temperate phage that upon
successful infection of its Vibrio host turns the bacterium into a fatal disease. By integrating
their DNA into the bacterial genome bacteriophages can transform an apparently stable
commensalism between Vibrio spp. and animal hosts into a highly virulent infection making
phages one of the most important drivers of virulence evolution across the animal kingdom.
However, such three-way interactions are often very complex and still poorly investigated.
Here I present first results from a three-way species interaction using a well-established
model system consisting of pipefish, Vibrio spp. and their temperate phages. In a crossinfection matrix of 75 Vibrio and 75 temperate phages three distinct groups of Vibrio bacteria
were found, i.e. (1) Vibrio that are susceptible to generalist and specialist phages, (2) Vibrio
that are only susceptible to specialist phages and (3) Vibrio that are resistant against any
phage infection. To further gain an integrative view across all three levels within this threeway interaction, we infected juvenile pipefish with bacteria stemming from one of the three
groups. By measuring gene expression, mortality and infection intensity first results show
that Vibrio, which are resistant to phages have a reduced infection intensity on pipefish. This
indicates that bacteria virulence towards pipefish is significantly dependent on Vibrio
susceptibility to phages, which emphasize the great importance of bacteriophages in
determining Vibrio virulence.