Bacterial symbionts confer physiological effects on eukaryotic hosts. The strain of bacteria, as well as the species can impact these effects. Contact-dependent competitive  mechanisms determine which strains are able to establish and maintain symbiosis with a host. One competitive method the Type VI secretion system, a nano-machine that delivers toxins that cause lysis. The  project studies interactions between different Type VI+ strains using the squid-Vibrio symbiosis as a model for symbiosis establishment and strain diversity.