In the Gibbs Lab, we utilize the bacterium Proteus mirabilis as a model system of self versus non-self recognition. We leverage its sophisticated synthesis of sensing, signaling, and motility to better understand the basic principles underpinning social behaviors; to identify and explore applications; and to bridge microbiology, cell biology, and biochemistry.

We aim to understand how cells and organisms distinguish between self and other. A Gram-negative bacterium, P. mirabilis is an opportunistic pathogen that causes urinary tract infections, most significantly in patients with long-term indwelling catheters. P. mirabilis populations display a remarkable phenomenon when migrating as a swarm across a surface: a visible boundary forms between swarms of different P. mirabilis strains. In contrast, swarms of the same strain do not give rise to a visible boundary and merge, indicating that P. mirabilis swarms are capable of territoriality and of self versus non-self recognition (see image).

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.

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