Lighting the way: how the squid– Vibrio model can inform thermal impacts on symbiotic dynamics

As global temperatures are shifting, so too is the landscape of organismal fitness and, by extension, the role of the symbiotic microbes they house. As these host-microbe partnerships grapple with changing environments, current research struggles to keep pace with the complexity of microbial symbioses acclimating, adapting and evolving as environmental conditions change around them. Wild-caught organisms have been used to test adaptation to extreme environments, but extrapolating and interpreting data on how separate partners within a symbiosis respond to detrimental conditions is difficult. The beneficial association between bobtail squids and bioluminescent Vibrio bacteria is a model that has been used for over three decades to uncover evolutionary and ecological mechanisms of symbiogenesis. The system is highly amenable to a broad range of physiological and molecular techniques and has been used to study many dimensions of symbiotic interactions. This beneficial association has demonstrated that host selection of environmentally available Vibrio symbionts can be influenced by various abiotic conditions, such as temperature. Complex biochemical communication has been charted extensively between host and symbiont, revealing universally conserved traits that are temperature sensitive. Additionally, temperature can influence co-evolution of the partners, and this system can be used to predict symbiotic cooperation over evolutionary time scales. While one model system cannot provide exhaustive insight, the bobtail squid-Vibrio mutualism has laid extensive, pioneering groundwork that can be used to develop targeted questions about symbioses under changing climates.