Identification of Bacterial Molecules in Interkingdom Signaling using a Novel High-throughput Screening Platform

Abstract

The coexistence of prokaryotes and eukaryotes in symbiotic and pathogenic relationships depends on the ability of both groups to detect and respond to one another’s secreted molecules. This process is known as interkingdom signaling, and was first used to describe eukaryotic detection of bacterial signaling molecules. However, few of these molecules have been identified, leaving the mechanisms of interkingdom interactions largely unclear. In a process called quorum sensing (QS), bacteria communicate within populations through the secretion and detection of molecules known as autoinducers (AIs). Caenorhabditis elegans, a well-characterized eukaryote with a sophisticated chemosensory system, detects and chemotax to a wide range of bacterial molecules, including bacterial AIs. C. elegans also chemotax to the pathogenic bacterium Vibrio cholerae and the primary V. cholerae AI CAI-1. In this study, we screen the V. cholerae genome to identify additional bacterial molecules that signal to C. elegans. Additionally, we demonstrate the development and use of a novel high-throughput screening platform that results in a 15-fold increase in mutant screening rate. In V. cholerae, we identified 34 candidate mutants that demonstrated altered ability to elicit C. elegans chemotaxis. 23 of the candidate genes are involved in QS, suggesting that bacterial QS may also regulate production and secretion of signals in interkingdom signaling. Additionally, we identified genes involved in toxin biosynthesis, secretion systems, and biofilm formation. These findings elucidate potential molecules and pathways through which bacteria communicate with eukaryotes, and provide insight on the mechanisms of interkingdom signaling and its roles in pathogenicity.