Examination of Pseudomonas aeruginosa lasI regulation and 3-oxo-C12-homoserine lactone production using a heterologous Escherichia coli system

Abstract

In Pseudomonas aeruginosa, the signaling molecule 3-oxo-C12-homoserine lactone (3OC12HSL) is synthesized by LasI, and lasI transcription is positively regulated by LasR. A heterologous model has been generated for the study of the LasRI/3OC12HSL regulatory network in Escherichia coli. Escherichia coli pAHL-BAC cultures produced LasI-synthesized acylhomoserine lactones (AHLs) at levels and with kinetics similar to what is observed in cultures of P. aeruginosa strain PAO1. Analysis of the lasI transcript also showed similar induction profiles in both the E. coli pAHL-BAC strain and P. aeruginosa. Transposon mutagenesis of pAHL-BAC confirmed that transcriptional regulation by LasR is necessary for 3OC12HSL production, and showed that artificially increasing lasI transcript levels leads to higher levels of 3OC12HSL. Previous studies have shown that P. aeruginosa 3OC12HSL inhibits hypha formation, but not growth, in Candida albicans, and the E. coli pAHL-BAC similarly inhibited filamentation when grown in coculture with the fungus. It is proposed that this system will be useful for the study of factors that impact lasI regulation and 3OC12HSL production, and for the examination of the role of LasI-produced AHLs in bacterial interactions with other organisms.