Models and approaches to dissect host–symbiont specificity

Animals are symbiotic superorganisms, composed of eukaryotic cells and specific microbial residents that perform essential functions for their host. As humans, we are beginning to appreciate the diversity and function of our own microbiota, but model systems are leading the field in illustrating the molecular mechanisms that allow specific relationships to be recapitulated during each host generation. This review focuses on models in which genetic screens, coupled with genomics, imaging, phylogenetics and population biology, have begun to allow a remarkably detailed investigation into the molecular dissection of the evolution of host specificity in animal symbionts.