Promoter Identification and Optimization for the Response of Lactobacillus plantarum WCFS1 to the Gram-negative pathogen-associated molecule N-3-oxododecanoyl homoserine lactone

Quorum sensing (QS) in bacteria has been a well studied cellular communication phenomenon for decades. In recent years, such systems have been repurposed for the use of biosensors in both cellular and cell-free contexts as well as for inducible protein expression in non-traditional chassis organisms. Such biosensors are particularly intriguing when considering the association between the pathogenesis of some bacteria and the QS signaling intermediates. Considering this relationship, and considering the recent demonstration of the species L. plantarum WCFS1 as both a synthetic biology chassis and an organism capable of detecting a pathogen-associated QS molecule, we wanted to develop this organism as a QS sentinel. Using an approach combining techniques from both systems and synthetic biology, we identified a number of native QS response genes and altered associated promoter activity to tune the output of L. plantarum cultures exposed to N-3-oxododecanoyl homoserine lactone. The resulting engineered QS sentinel reinforces the potential of modified Lactic Acid Bacteria for use in human health promoting applications, and also demonstrates a simple rational workflow to engineer sentinel organisms to respond to any environmental or chemical stimuli. Overall design: L. plantarum was treated with 3OC12 at OD600 of 0.5 and RNA was extracted after one doubling for transcriptomic analysis.