Vibrio 2009, the third international conference on the biology of Vibrios, was held in Rio de Janeiro, Brazil, in November 2009. This conference united researchers studying various aspects of pathogenesis, symbiosis and environmental persistence of this diverse group of marine bacteria. Through many of the presentations, it became apparent how horizontal gene transfer and genetic flexibility has driven the incredible diversity of these microbes. Interestingly, unifying themes of behaviour could be seen in the interaction(s) of Vibrios with other organisms, such as with other bacteria, corals, invertebrates and humans. Presentations illuminated the idea that the path towards symbiosis is not that different from the path towards disease, and that alterations in environmental conditions, such as climate change, can tip the balance and change the Vibrio interactions from benign to pathogenic.