Eavesdropping on Marine Microbial Communication: Influence of Quorum Sensing on the Vibrio campbellii Exometabolome

摘要

Quorum sensing (QS) enables bacteria to communicate and sense their population density by using small molecules -- when a quorum is reached, these unicellular organisms can synchronize their behavior, acting like a multicellular organism. Due to our interest in marine microbial ecology, we sought to explore this small molecule chemical communication with LCMS-based metabolomics, using the QS model system Vibrio campbellii. We eavesdropped on the V. campbellii conversation by studying the molecular "words" between bacteria in the extracellular space (untargeted "exometabolomics" or "secreted metabolomics") as a function of population density. To determine conversation changes dependent on a known QS pathway, we compared exometabolites of wild-type (WT) V. campbellii to a deletion mutant lacking the QS transcriptional regulator LuxR (ΔluxR). Untargeted marine exometabolomics was found to be particularly challenging due to the under-exploration of marine microbial chemistry (and hence low abundance in metabolomics databases) and the relatively high levels of media salts and glycerol from which exometabolites had to be extracted. We found that potential signaling molecules indole-3-carboxaldehyde and several diketopiperazines, as well as serine-lipids from amphi-enterobactin siderophores, were differentially produced in WT versus ΔluxR V. campbellii.