Mikrobielle Okologie N-Acyl-L-Homoserinlacton-produzierender Bakterien in der Rhizosphare von Tomatenpflanzen
b'N-Acylhomoserinlactones (AHL) are signalling molecules in gram-negative bacteria, which regulate, in a cell density dependent way, important interactive functions. This phenomenon is known as quorum-sensing.\\nThis work characterised the microbial ecology of the autoinducer (AHL) producing bacteria Serratia liquefaciens MG1 and Pseudomonas putida IsoF in the rhizosphere of tomato plants. Gfp- and rfp-tagged strains of the AHL producing wiltypes S. liquefaciens MG1 and P. putida IsoF were compared with its AHL-negative mutants, which were unable to produce AHL. Two kinds of plants cultivating systems were used: a defined axenic system and a complex soil system. The characterisation of the root colonisation behaviour was performed using confocal laserscanning microscopy (CLSM) and cell counting of bacteria. Fluorescence in situ hybridisation (FISH) and terminal restrictions fragment length polymorphism (t-RFLP)-techniques were used to examinate shifts of the bacterial population in the rhizosphere on tomato plants. The effective in situ production and spreading of AHL on tomato roots was demonstrated with P. putida IsoF using an AHL-sensor strain P. putida F117 pKR-C12. AHL was produced in effective concentrations in the rhizosphere of tomato plants and influenced the bacterial rhizosphere population. However, the AHL-production had no influence on the colonization behaviour of the AHL-producing strains S. liquefaciens MG1 and P. putida IsoF.'