Short introduction to current research topic:

Dynamic Regulation of N-Acyl-homoserine Lactone Production and Degradation in Pseudomonas putida IsoF

The biocontrol strain Pseudomonas putida IsoF, which was isolated from a tomato rhizosphere, is a known N-acyl-homoserine lactone (AHL) producer with only one LuxI/LuxR like quorum sensing system. The production and degradation of AHLs was analysed in different growth phases of the bacterium. With the analytical tools of ultra performance liquid chromatography and high resolution mass spectrometry it was possible to determine not only the various AHLs synthesized over time but also their degradation products. 3-oxo-decanoyl-homoserine lactone was found to be the dominant AHL which reached its maximum already in the early logarithmic growth phase. Although the pH of the medium was neutral, the AHLs were degraded thereafter rapidly to the corresponding homoserines and other metabolites. The proposed lactonase gene of P. putida IsoF could not be identified, because it is apparently quite different to hitherto described lactonases. The analytical data were used to calculate rates and thresholds of AHL production by mathematical modelling allowing quantitative predictions and further understanding of the quorum sensing based regulations in this bacterium. This study combining microbiological, chemical and mathematical approaches suggests that AHL degradation is an integral part of the whole autoinducer circuit of P. putida IsoF.

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