Sociomicrobiology, or study of bacterial social behaviors, has garnered significant attention over the last decade. It is now well established that bacteria exhibit many social activities coordinated by complex inter- and intra-species cell-cell signaling systems commonly referred to as quorum sensing systems. However, understanding of how quorum sensing mediates social behavior is still incompletely understood, particularly in regard to signal dissemination. One fundamental aspect of signal dissemination is the movement of signals into the extracellular milieu by active or passive means. Once in the extracellular environment, bacteria use these signals to communicate with each other and coordinate their activities.
The Gram-negative bacterium Pseudomonas aeruginosa serves as a model bacterium for studying bacterial cell-cell communication. Quorum sensing in P. aeruginosa involves multiple signals including 2-heptyl-3-hydroxy-4-quinolone (PQS). Dr. Whiteley recently discovered that PQS is packaged into P. aeruginosa outer membrane vesicles (MVs) and these MVs serve to disseminate this signal within a population. Not only is PQS packaged within MVs, but this molecule is also required for MV formation. There are three goals for this research project: i) elucidate the mechanism of MV formation in P. aeruginosa, ii) determine the role of MV-mediated signal dissemination in modulating P. aeruginosa group behavior in a biofilm, iii) examine the ubiquity of MV-signal packaging in prokaryotes.
As a broader impact of this study, Dr. Whiteley has established collaborations with Langston University to provide summer research opportunities for minority undergraduate students. Langston University is the only Historically Black College/University in Oklahoma. Each year 10-12 Langston students who are actively pursuing summer research opportunities cannot identify a laboratory to host them. Through collaborative efforts between Dr. Whiteley and Langston University, two Langston undergraduate students will be selected each summer for research in Dr. Whiteley's laboratory to participate on the proposed projects.
Over the last two decades, the field of bacterial communication has received significant attention, and it is clear that coordinating bacterial group behavior is an important and complex issue. The observation that bacteria mediate cell-cell signaling using MVs illustrates a novel mechanism for signal dissemination in a prokaryote and enhances the understanding of how prokaryotes coordinate group behavior. These results have important implications for communication biology as they significantly impact the quorum sensing paradigm of signal dissemination. This study will also provide minority students who are interested in pursuing graduate studies in the biological sciences with exposure to the most recent research in bacterial communication.
In summary, the ultimate goals of this proposal are two-fold: 1) to enhance our understanding of bacterial social behaviors through examination of the roles of PQS-mediated MV formation; 2) provide minority undergraduate and graduate students who are interested in microbiology and biochemistry with the opportunity to learn the kinds of skills necessary to develop testable hypotheses which will foster their natural curiosities.
