In nature, bacteria often exist as members of complex communities called biofilms. Cells interact within biofilms, sending signals to each other and changing their behavior in response. Understanding how bacteria interact with each other and with their hosts is a fundamental challenge in biology. Molecular analysis of cell-cell interactions in mixed populations of bacteria is difficult. In contrast, certain bacteria like Myxococcus xanthus readily form biofilms in which cells interact extensively. When starved, M. xanthus cells move to aggregation centers and construct a nascent fruiting body. Within the fruiting body, rod-shaped cells differentiate into spherical, dormant spores. Studies of C-signaling during M. xanthus development are establishing a new paradigm for how bacterial cells can interact. C-signaling involves CsgA, a protein produced in the developing cells that becomes associated with the cell surface. It has been proposed that a proteolytic fragment of CsgA serves as a signal upon end-to-end contact between cells. C-signaling induces several responses in recipient cells. It regulates cell movements, gene expression, and sporulation. Intriguingly, the different responses to C-signaling require different levels of CsgA, and the level of CsgA rises during development. Therefore, C-signaling appears to dictate the order of events during the middle to late stages of development. The long-term goal of this project is to determine the molecular mechanisms of developmental gene expression in response to C-signaling. The broader impact of the research is that it will provide paradigms for how bacteria might interact in biofilms. The insights gained will find application in environmental cleanup, industrial processes, agricultural practices, and animal health. Also, the research will contribute to the development of human resources in science through the training of undergraduates, graduate, and postdoctoral students.
