Detection of Quorum-Sensing Molecules in the Mutualistic Bacteria Vibrio fischeri Exposed to Simulated Microgravity Using Cell-Based Biosensors.

Bacteria flourish in multiple environments when communicating with each other in a process known as Quorum Sensing. This process is accomplished by the production of small signaling molecules referred to as Autoinducers (AI). This communication allows the bacteria to alter their gene expression in an effort to regulate their cell number, behavior, community formation and virulence. The space environment provides stressful conditions for bacteria as they are exposed to radiation and Microgravity (µG or MG) altering synthesis and concentration of Autoinducers. The purpose of this research was to expose the model system Vibrio fischeri to simulated microgravity using the recently developed analog EagleStat, and measure production of AI via three cell-based biosensors (genetically modified microorganisms) that are able to detect long, medium and short chain Autoinducers after activation of gene expression of fluorescent markers. Our results show selective expression of Autoinducers after 24 or 48 hours of incubation. Medium and Short chain AIs are detected in higher quantities after 24 hours whereas long chain AIs are detected in higher quantity after both 24 and 48 hours of incubation. Although there is an observed tendency of a higher synthesis of AIs under Microgravity, our findings show that there is not a significant difference between Gravity and Microgravity conditions. These data are of great significance to decipher bacterial communication under stress conditions, and sheds light into future studies in an effort to elucidate bacterial responses to Microgravity.