The goal of our research is to understand how cells and organisms distinguish between self and other. Specifically, we are investigating the molecular mechanisms underlying the ability of cells to discriminate self from non-self in the uropathogen Proteus mirabilis. The 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 can form crystalline biofilms and can cause the formation of kidney stones in patients. 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.
This self vs non-self recognition behavior in P. mirabilis is similar to allorecognition in eukaryotic cells and is analogous to territoriality in larger organisms. Conspecific self vs non-self recognition is widely found throughout biology, including E. coli, Plasmodium, 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?
Recently we have identified a genetic locus in P. mirabilis that encodes components necessary for self vs non-self recognition and for the definition of strain-specific identity. We utilize approaches to microbiology, cell biology, molecular biology, and biochemistry to further dissect the role of these identified genes in self vs non-self recognition and moreover to understand the molecular mechanisms of social behaviors in bacteria.