This self-recognition behavior in P. mirabilis is similar to allorecognition in eukaryotic cells and is analogous to territoriality in larger organisms. Conspecific self recognition is widely found throughout biology, including Escherichia coli, plant roots, marine chordates, and vertebrate immune systems. Connecting these is a fundamental question: how does a cell recognize and differentiate self from non-self? We have identified multiple gene clusters in P. mirabilis that encodes components necessary for self recognition and for the definition of strain-specific identity. Our current model suggests that P. mirabilis detect the absence of self-identifying markers as the presence of non-self cells. In the Gibbs Lab, we employ experimental approaches from microbiology, cell biology, molecular biology, and biochemistry to further dissect the role of these gene clusters in self recognition, cell physiology, and population, dynamics, all leading to a more in-depth understanding of social behaviors.