Our primary research interests concern beneficial symbiotic interactions between bacteria and either invertebrates or plants. Symbiotic bacteria are fundamental to the survival of many multicellular organisms, yet we are only now beginning to fully appreciate the diversity and pervasiveness of microbial partnerships with higher organisms. These symbioses, at the heart of our research program, represent the extreme ways by which microbes have had a profound effect on their hosts, including changes in morphology, physiology, ecology, and even evolution. Many symbiotic partnerships have allowed organisms to exploit environments that are not generally available to most and have resulted in unusual adaptations by both partners. We study these associations, many of which remain largely unexplored, from different perspectives, including the evolution of unusual host structures, symbiont genome structure and content, novel physiological and biochemical capabilities of both partners, and unique ecological adaptations.