Most children are taught that germs (microbes) will make them sick, and indeed, some can. However, the more common natural relationship between animals and microbes is mutually beneficial (mutualistic) since microbes are absolutely necessary for normal animal development, nutrition, and immunity. In these associations microbes typically colonize discrete locations on or within the animal. Little is as yet understood regarding the distinct physical nature of such colonization sites, or how beneficial animal-microbe associations are formed and maintained. It is known that these processes rely on animal-microbe communication that can involve chemical signals exchanged from a distance, as well as signaling through direct physical contact. Still lacking is a fundamental understanding of the identities of signals, how and where they are produced, how they are recognized, and the effects they mediate in each partner. To begin to address these questions, the proposed research focuses on an emerging model of animal-microbe mutualism between a small, soil-dwelling nematode (roundworm) and the beneficial bacterium (symbiont) with which it associates. The bacterial symbiont lives in a specific vesicle (receptacle) within the intestine of the nematode, and is the only microbe capable of residing at this location and establishing a relationship with the nematode; in other words, it is the only microbe that can correctly communicate with the nematode to achieve a mutually beneficial relationship. In this study the morphological and developmental features of the nematode intestinal vesicle will be analyzed to better understand the colonization process. The proposed research will also explore new hypotheses regarding the chemical signals and the physical interactions that occur between the nematode and the symbiont and how these interactions might affect the physiology of each organism. Furthermore, the proposed research will address questions of how such intimate animal-microbe associations evolve.
The specific goal of this proposal is to characterize, using microscopy, biochemistry, and microbial genetics, the structure and development of the interaction between the nematode and the symbiont and how each partner contributes to this relationship. The model system being studied is easily studied in the laboratory. The three labs involved in this collaborative research are each contributing distinct expertise required for the proposed studies. Together these labs will:
1) Analyze, using microscopy and biochemistry, the physical aspects of the nematode intestinal region that interacts with the microbial symbiont; 2) Compare the intestinal structures of different nematodes to understand how the ability to specifically interact with the symbiont evolved; 3) Study how the intestinal region that interacts with the symbiont develops, and how the symbiont affects this development; and 4) Characterize, using biochemistry and genetics, the chemical signals exchanged between the nematode and the symbiont.
This model system is well suited for education because of its broad relevance to agricultural, medical, and basic research and multiple disciplinary perspectives. An underrepresented minority undergraduate has contributed to preliminary research, and each lab will continue to train and educate students from diverse backgrounds. A workshop will be held that includes data and techniques developed through this research. Finally, this study will enhance a K-12 teaching tool developed as part of the NSF-funded K through Infinity program at UW-Madison.
