The digestive-tract community of animals has been hypothesized to play important roles for the well-being of the host. The inherent complexity of most of these communities has hindered progress in understanding the molecular mechanisms that are critical for bacterium-host and bacterium-bacterium interactions. A CAREER grant has been awarded to Dr. Joerg Graf of the University of Connecticut to lay the foundation for using the medicinal leech as a model for digestive-tract associations. This leech houses two simple, multispecies digestive-tract communities. The microbial community of the crop, which is the largest compartment of the digestive tract, is dominated by Aeromonas veronii biovar sobria and a presently uncultured symbiont related to Bacteroides. The community of the intestinum is more complex with five species accounting for over 88% of the detected 16S rRNA genes. Dr. Graf will use a state-of-art technique, signature-tagged transposon mutagenesis, to identify genes that Aeromonas veronii requires for successful colonization. This analysis will provide new insights into the molecular mechanisms and physiological adaptation critical for establishing and maintaining a successful symbiosis. The location of the symbionts in the crop and intestinum will be determined using fluorescent in situ hybridizations. Fundamental questions will be investigated, including the function of the symbionts and the way the symbionts are transmitted between generations. This research program will be closely integrated with two educational components. A workshop in genetic engineering will be developed for high school students that participate in the Mentor Connection, a summer program at the University of Connecticut for talented juniors and senior of diverse backgrounds. In addition, a bacterial genetics laboratory class for undergraduate students will be developed that uses organisms and techniques used in this research program. Dr. Graf's work will provide important information that is applicable to more complex digestive-tract associations and train the next generation of scientists.
