The Stabb Lab:     Researchers in Dr. Eric Stabb's lab study the light-organ symbiosis between the bioluminescent bacterium Vibrio fischeri and the squid Euprymna scolopes, as a model for natural bacteria-animal interactions. E. scolopes hatchlings lack V. fischeri, which they must obtain from their surroundings.  After infection, the squid carry V. fischeri, and only this bacterium, in epithelium-lined crypts of a specialized light-emitting organ. Several features make this symbiosis uniquely tractable. Notably, this natural infection can be reconstituted in the lab, so we are able to observe the bacteria and their gene expression in an ecologically relevant context inside its host.

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One focus of the lab is how V. fischeri cells communicate using pheromone signals.  Such bacterial signaling is often termed "quorum sensing" and is typically depicted as regulation in response to high cell density or "quorum".  However, it is now clear that the pheromones are not simply census-taking molecules and can perform more complicated social roles.  The pheromones in V. fischeri control the lux genes responsible for bioluminescence, and the pheromones are controlled by themselves in positive-feedback loops and by environmentally responsive regulators, including ArcA/ArcB, Crp, Fur, and others.  This raises the intriguing possibility that in addition to reflecting cell density, bacterial pheromones may coordinate behaviors, such as the group decision to bioluminesce, in response to local environmental cues.  Interestingly, bioluminescence is induced upon entering the symbiosis, and dark (lux) mutants are attenuated in colonizing the E. scolopes light organ; however, the symbiotic role of bioluminescence remains unclear.   Studying pheromone-mediated regulation may help shed light on the purpose of bioluminescence.  We have embarked on a collaborative project to model and understand how V. fischeri uses multiple pheromones to underpin its cell-cell communication.

A second major focus of the lab is aimed at understanding the interspecies signaling by which the squid host recognizes and responds to V. fischeri.  Peptidoglycan and LPS can trigger changes in host development that parallel those seen during normal symbiotic infection.  We are interested in how and why V. fischeri releases peptidoglycan monomer, which acts as a morphogen on the host.  Currently, a project in the lab is using V. fischeri as a model to understand how new peptidoglycan structures can evolve in bacteria.

Many projects in the lab are underpinned by genetic approaches, and we are often developing genetic and genomic tools for V. fischeri.  For example, characterizing the small V. fischeri plasmid pES213 led to an array of shuttle vectors that is still expanding.  We have also pioneered improved methods for mutagenesis with mini-Tn5 in V. fischeri.

Finally, everyone in the Stabb lab contributes to the teaching mission at the University of Georgia, and we are involved in outreach efforts to K-12 students, spreading the word of the power of microbes and the wonders of bioluminescence.  Three Stabb labbers [Noreen Lyell, Richard M. (Mark) Jones, and Julie Stoudenmire] have earned the prestigious UGA Excellence in Teaching Award, which is given to only five teaching assistants across the entire university each year.  

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