Bacteria are notorious for causing disease and increasingly becoming appreciated for their beneficial roles in health. Bacteria can exist as free-swimming cells or as members of surface-attached communities called biofilms. Biofilms are particularly detrimental to human health. Transitions between these lifestyles are controlled by the cell-cell communication process called quorum sensing (QS). QS relies on the production, release, accumulation, and detection of extracellular signal molecules called autoinducers (AIs). QS enables bacteria to orchestrate collective behaviors including biofilm formation and dispersal. A bacteriophage was recently discovered that hijacks a bacterial QS AI and uses the information encoded in it to drive transitions between lysis and lysogeny, the first report of phage-bacterial QS-mediated inter-kingdom-communication. The phage QS receptor called VqmAPhage enables the phage to ?tune into? the accumulation of the cognate host QS AI, 3,5- dimethylpyrazin-2-ol (DPO). This eavesdropping mechanism allows the phage to execute its lytic cycle exclusively at high host cell density, presumably maximizing phage spread. Moreover, this mechanism enables the phage to drive the host bacterial biofilm dispersal program.
My aims are to understand the molecular basis and biological significance of this newly-discovered phage QS cross-communication process in contexts that mimic nature: non-uniform spatially structured phage-bacterial biofilm communities. I hypothesize that the phage QS receptor is produced immediately following infection providing incoming phages the first indication of host cell density, enabling the phage to appropriately launch either the lysis or the lysogeny program upon entry. I will define when this pathway is activated following infection. Second, I hypothesize that the natural, host-produced inducer of vqmAPhage expression primes a positive feedback loop that promotes the rapid transition of the phage to the lytic phase exclusively at high host cell density. I will identify the endogenous inducer of vqmAPhage transcription and explore the role of the inducer in phage and host biology. Finally, I predict that phage-mediated lysis occurs primarily at the highest cell density regions of biofilms, promoting both host dispersal and increased phage spread to new host cells. I will define the spatial and temporal dynamics of phage QS-mediated lysis in biofilms and I will monitor the consequences to the biofilm, to phage transmission, and to host cell dispersal. Collectively, my work will define phage-bacterial inter-kingdom interactions that occur through QS. My findings could also contribute to the development of new approaches to control bacterial infections, either through phage therapies, biofilm disruption strategies, or a combination of the two approaches. To accomplish the goals of this project, I will become expert in molecular biology, bacterial genetics, imaging technologies, scientific writing, seminar speaking, teaching, and mentoring. The skills I master as I make discoveries as a postdoctoral fellow will be crucial to prepare me to establish my own independent academic laboratory focused on investigations of phage-bacterial communities.
Biofilms are a predominant form of bacterial life on Earth with ramifications, both beneficial and harmful, in medicine, industry, and the environment. The newly discovered viral quorum-sensing-eavesdropping system that I am studying will reveal the mechanisms underlying bacterial-phage interactions in biofilms and their connections to quorum-sensing-mediated communication. Insights gained from this investigation could inform the development of phage therapies and/or biofilm disruption strategies for the treatment of biofilm-based human diseases.
