RESEARCH PAPER Analysis of N-acylhomoserine lactone dynamics in continuous cultures of Pseudomonas putida IsoF by use of ELISA and UHPLC/qTOF-MS-derived measurements and mathematical models Katharina Buddrus-Schiemann & Martin Rieger & Marlene Mühlbauer & Maria Vittoria Barbarossa & Christina Kuttler & Burkhard A. Hense & Michael Rothballer & Jenny Uhl & Juliano R. Fonseca & Philippe Schmitt-Kopplin & Michael Schmid & Anton Hartmann Received: 26 March 2014 /Revised: 24 June 2014 /Accepted: 24 July 2014 /Published online: 13 August 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract In this interdisciplinary approach, the dynamics of production and degradation of the quorum sensing signal 3- oxo-decanoylhomoserine lactone were studied for continuous cultures of Pseudomonas putida IsoF. The signal concentra- tions were quantified over time by use of monoclonal antibodies and ELISA. The results were verified by use of ultra-high-performance liquid chromatography. By use of a mathematical model we derived quantitative values for non- induced and induced signal production rate per cell. It is worthy of note that we found rather constant values for dif- ferent rates of dilution in the chemostat, and the values seemed close to those reported for batch cultures. Thus, the quorum- sensing system in P. putida IsoF is remarkably stable under different environmental conditions. In all chemostat experi- ments, the signal concentration decreased strongly after a peak, because emerging lactonase activity led to a lower concentration under steady-state conditions. This lactonase activity probably is quorum sensing-regulated. The potential ecological implication of such unique regulation is discussed. Keywords Pseudomonas putida IsoF . Continuous culture . N-acylhomoserine lactones . Mathematical modelling . ELISA . Quorum sensing Introduction For an increasing number of bacterial strains, cell-to-cell communication, called quorum sensing (QS) [1], has been reported to be of fundamental importance in adapting to environmental changes. These bacteria regulate gene expres- sion via small diffusible signal molecules, called autoinducers (AI), which are released into the environment [2, 3]. The concentration of signaling molecules in the cell environment increases when the bacterial population density increases. As soon as a specific cell density threshold has been reached, AI molecules bind to a transcriptional regulator that activates Electronic supplementary material The online version of this article (doi:10.1007/s00216-014-8063-6) contains supplementary material, which is available to authorized users. K. Buddrus-Schiemann : M. Rieger : M. Mühlbauer : M. Rothballer : M. Schmid : A. Hartmann (*) Research Unit Microbe-Plant Interactions, Helmholtz Zentrum München, German Research Centre for Environmental Health (GmbH), Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany e-mail: anton.hartmann@helmholtz-muenchen.de M. V. Barbarossa Bolyai Institute, University of Szeged, Aradi vértanúk tere 1, 6720 Szeged, Hungary C. Kuttler Centre for Mathematical Sciences, Technische Universität München, Boltzmannstrasse 3, 85748 Garching, Germany B. A. Hense Institute of Computational Biology, Helmholtz Zentrum München, German Research Centre for Environmental Health (GmbH), Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany J. Uhl : J. R. Fonseca : P. Schmitt-Kopplin Research Unit Analytical BioGeoChemistry, Helmholtz Zentrum München, German Research Centre for Environmental Health (GmbH), Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany P. Schmitt-Kopplin Analytical Food Chemistry, Technische Universität München, Alte Akademie 10, 85354 Freising-Weihenstephan, Germany Anal Bioanal Chem (2014) 406:6373–6383 DOI 10.1007/s00216-014-8063-6