Detection and quantification of quinolone signalling molecule: A third quorum sensing molecule of Pseudomonas aeruginosa by high performance-thin layer chromatography

Sophisticated network of quorum sensing involves the production of chemical signals which regulate the combined expression of virulence genes and biofilm formation in Pseudomonas aeruginosa. Two well-characterized acyl homoserine lactone based las and rhl systems together with alkyl quinolone based Pseudomonas quinolone signalling (PQS) are fundamental components of this network. Third signalling molecule, 2-heptyl-3-hydroxy-4-quinolone (PQS) is of paramount importance because of its interconnecting role in quorum sensing hierarchy in P. aeruginosa. Accurate detection of PQS molecule is very important to understand the involvement of this system in infection process of P. aeruginosa. In this study, high performance-thin layer chromatography (HP-TLC) method was developed for detection as well as quantification of PQS signal molecules in P. aeruginosa, which combines conventional method like TLC with sophisticated instrumentation. This method was validated using parameters like linearity, accuracy, precision, reproducibility and sensitivity. Intra- and inter-day accuracy and precision values were determined which were found to be within acceptable level and hence showed reproducibility. Measurement of PQS in the range of 0.01 nmol indicated excellent sensitivity of this approach for quantifying PQS molecule. Automated sampling, rapid and simultaneous analysis of large number of samples and minimal errors make this method more suitable for analysis of PQS signalling molecules. Production of PQS was found to be strain dependent since variation in amount of PQS was observed among different P. aeruginosa isolates. Further, PQS production was also dependent on growth phase of P. aeruginosa with maximum production in late stationary phase.