Sensory Regulation of Bacterial Behaviors

Photo sensing in non-photosynthetic bacteria

Light is detected by photoreceptors in all domains of life. Surprisingly, photosystems in non-photosynthetic bacteria are mostly undefined. We have identified an entire photo-sensing signaling cascade in the human pathogen Pseudomonas aeruginosa —light as the input, BphP as the detector, AlgB as the signal transducer, and biofilm formation and virulence factor production as the outputs — enabling crucial insight into light-driven control of bacterial behaviors. We are characterizing the photo-sensing system and its regulon in P. aeruginosa and exploring the role of photo sensing in P. aeruginosa-host interactions. Going forward, we will test the generality/specificity of our findings in P. aeruginosa by expanding our research to include other bacteria that possess the BphP-AlgB photo-sensing system.

Nutrient sensing in biofilms

Nutrient availability is a key sensory cue that governs different stages of the biofilm development cycle. The CbrA/CbrB two-component system is involved in nutritional adaptation in P. aeruginosa and modulates biofilm development by mechanisms that are poorly defined. In this project, we are delineating the molecular players downstream of the CbrA-CbrB cascade to gain a better understanding of how nutrient status influence key steps of biofilm development.

Quorum sensing and biofilm development

Quorum sensing, a cell-to-cell chemical communication process mediated by the production and detection of small molecules called autoinducers, allows bacteria to coordinate their behaviors. We have discovered that the RhlR-dependent quorum sensing system in P. aeruginosa represses biofilm formation. However, we found that RhlR controls over 300 genes in biofilms and represses biofilms in multiple ways. In this project, we seek to define these mechanisms.

Sensing other bacteria

Bacteria rarely exist in isolation. Rather they live in polymicrobial communities in which they interact, and these interactions are relevant in the environment and during disease. In this project, we want to understand how a particular bacterium senses the presence of other bacteria, whether the interactions are synergistic or competitive, and what signaling molecules are used to communicate with one another,

Convergence of sensory signaling pathways

It is imperative that bacteria decode and integrate varied sensory inputs to make key transitions such as whether to launch a virulence program or remain in a stealth mode to avoid host immune factors. However, how bacteria integrate diverse sensory information is poorly understood. Our goal is to identify the components that connect different signaling pathways. To pursue this goal, we will define how information from photo sensing, nutrient sensing and quorum sensing is combined at the molecular and cellular scales to control bacterial behaviors.