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.
One focus of the lab is the regulation and symbiotic role of bioluminescence. The lux genes responsible for bioluminescence are induced upon entering the symbiosis, and dark (lux) mutants are attenuated in colonizing the E. scolopes light organ. The lux genes are controlled in part by a cell-density dependent pheromone-mediated regulatory circuit often referred to as "quorum sensing". However, bioluminescence is not simply regulated by cell density. Environmentally responsive regulators, including ArcA/ArcB and others, also strongly influence bioluminescence and pheromone (autoinducer) production. This raises the intriguing possibility that in addition to reflecting cell density, bacterial pheromones may coordinate behaviors in response to the environment. The Stabb lab is elucidating the complexities of this regulatory web, the environmental factors that ultimately govern lux regulation, the significance of pheromone-mediated communication in these bacterial populations, and the physiological relevance of bioluminescence for the bacteria.
Other research is aimed at understanding the interspecies signaling by which the squid host recognizes and responds to V. fischeri. LPS and peptidoglycan can trigger changes in host development that parallel those seen during normal symbiotic infection. Our lab is interested in unique elements of the V. fischeri LPS and in understanding how and why V. fischeri releases peptidoglycan monomer.
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. We are also involved in outreach efforts to K-12 students, spreading the word of the power of microbes and the wonders of bioluminescence.