The biocontrol strain studied in this thesis is Pseudomonas chlororaphis strain PCL1391, which controls tomato foot and root rot caused by Fusarium oxysporum f. sp. radicis-licopersici (Chin-A... Show moreThe biocontrol strain studied in this thesis is Pseudomonas chlororaphis strain PCL1391, which controls tomato foot and root rot caused by Fusarium oxysporum f. sp. radicis-licopersici (Chin-A-Woeng et al., 1998). Production of the anti-fungal metabolite phenazine-1-carboxamide (PCN) and an efficient root colonizing ability (Chin-A-Woeng et al., 2000) are crucial for efficient biocontrol by P. chlororaphis strain PCL1391. This thesis aims at the identification and analysis of environmental conditions affecting the production of PCN and the identification of novel genes involved in the regulation of PCN production. Show less
A general overview of regulation of secondary metabolism in Pseudomonas species is given in Chapter 1. Several approaches were combined to identify novel genes involved in the regulation of PCN... Show moreA general overview of regulation of secondary metabolism in Pseudomonas species is given in Chapter 1. Several approaches were combined to identify novel genes involved in the regulation of PCN synthesis and to study their interactions with other regulators. Site-directed mutagenesis was used to test the hypothesis that rpoS is a regulatory gene of PCN synthesis (Chapter 2). To discover additional genes in the regulatory cascade, which already contains psrA and rpoS, a random DNA-fragment microarray of the PCL1391 genome was constructed and used for transcriptomics of the psrA and rpoS mutants (Chapter 3). A random mutagenesis approach resulted in the identification of pip, a novel gene that stimulates PCN production in PCL1391 (Chapter 4). Analyses on the role of Pip as a switch of PCN production depending on environmental conditions are described in Chapter 5. The results described in this thesis are summarized in Chapter 6, where in addition the regulatory network of PCN synthesis in P. chlororaphis PCL1391 is compared to regulatory networks of secondary metabolism in other Pseudomonas species. Show less
