Investigating the Function of LuxT: A Quorum-Sensing Transcription Factor in Vibrio species

Abstract

Bacteria coordinate population-wide gene expression using a cell-cell communication process called quorum-sensing (QS). QS involves the production, release, and group-wide detection of small molecules called autoinducers. In the model marine bacterium Vibrio harveyi, the QS regulatory system relies on the production of five small regulatory RNAs (Qrr1-5) that are produced at low cell density when autoinducer concentrations are low. Recently, the Bassler group identified LuxT as a transcriptional repressor of qrr1, encoding one of the Qrr sRNAs. The possibility that LuxT regulates genes in addition to qrr1 has not been investigated. This thesis aims to further the understanding of the role of LuxT through primary literature research regarding QS and LuxT and analysis of transcriptomic studies. RNA-Sequencing data revealed that LuxT regulates 264 genes in V. harveyi, including genes necessary for type III secretion, type VI secretion, siderophore production, and production of the aerolysin pore-forming toxin, all of which are known virulence factors in Vibrio bacteria. These results demonstrate that LuxT is a global regulator in V. harveyi and the findings highlight the interconnected relationship between QS and virulence. Because LuxT is conserved among Vibrios, it is predicted that LuxT regulates the same behaviors in other species, including in the human pathogens Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus. Thus, this study is particularly relevant to public health initiatives that aim to develop novel therapies for combating bacterial diseases and address the antibiotic resistance crisis.