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Introduction interfere with salicylic acid-depending defense mechanisms. An induction of plant defense can not be excluded in general, even though no role for bacterially produced salicylic acid could be demonstrated in rhizobacterial induction of systemic resistance in Arabidopsis (Ran et al., 2005). Finally, the type of siderophores produced by a bacterium influence the damage caused by oxidative burst. The ROS formation during oxidative burst favors occurrence of the Fenton reaction, yet not only free iron interacts, but also iron-ligand complexes. Structural features of the ligand as well as the ligand : iron ratio varies the reaction characteristics of the radical formation (Engelmann et al., 2003). For example, Dikeya chrysanthemi produces the high-affinity siderophore chrysobactin. This catechol-type siderophore can form radicals during oxidative burst (Hirai et al., 2005). In addition D. chrysanthemi produces a low-affinity siderophore called achromobactin, which does not form radicals (Expert, 1999). So, siderophores are supposed to be involved in induction as well as in survival of plant defense reactions. 2.3 Biological control of bacterial blight of soybean The plant-microbe interaction between soybean (Glycine max) and the bacterial blight pathogen P. syringae pv. glycinea (Psg) has been used extensively as a model system to investigate plant pathogen relationships. Virulence factors of the pathogen have been elucidated and detailed studies on their regulation are available (Bender, 1999; Smirnova & Ullrich, 2004; Weingart et al., 2004). Furthermore, the defense response of soybean toward compatible and incompatible strains of the pathogen has been studied and the impact of pathogen signaling was examined (Cui et al., 2005; Zou et al., 2005). All this luxuriant background information makes this pathosystem an especially feasible model for investigation of biological control. Even the third player is already known: The antagonist Pseudomonas syringae pv. syringae strain 22d/93 (Pss22d) has been identified as an efficient biocontrol agent against Psg in vitro, in planta and - most importantly - under field conditions (May et al., 13
Introduction 1997a; May et al., 1997b; Völksch et al., 1996; Völksch & May, 2001a). What is lacking for our understanding of this biocontrol system is the determination of the control principles involved. In the following, a review of the available information is given. Pseudomonas syringae is a plant associated bacterial species belonging to the γ -subgroup of proteobacteria. It stains Gram-negative. Different strains can by either saprophytic or plant-pathogenic and are divided into more than 50 different pathovars (pv.) according to their host range (Doudoroff & Palleroni, 1974). The pathogen Psg has been discovered in 1919 as a leaf spot pathogen causing necrotic spots surrounded by chlorotic halos (Fig.4) that are developed Fig. 4. Bacterial blight of soybean. Typical symptoms of Pseudomonas syringae pv. glycinea infected soybean leafs: Leaf spots surrounded by chlorotic halos that develop into lesions later on. The picture is taken from the first publication describing this disease. The title page shown on the right. Source: Coerper, 1919) 14
Page 1 and 2: Siderophore production of Pseudomon
Page 3 and 4: Acknowledgements This project was s
Page 5 and 6: Abbreviations Ach achromobactin-lik
Page 7 and 8: Contents 4.1.2 Pseudomonas syringae
Page 9 and 10: Contents 5.3 Influence of sideropho
Page 11 and 12: Introduction 2 Introduction Like hu
Page 13 and 14: Introduction In contrast to the rhi
Page 15 and 16: Introduction 2.1.2 Host, pathogen a
Page 17 and 18: Introduction The relationship betwe
Page 19 and 20: Introduction developement of resist
Page 21: Introduction Fe 2+ + H 2 O 2 → Fe
Page 25 and 26: Introduction Pss22d demonstrated a
Page 27 and 28: Introduction 2.4 Aim of this study
Page 29 and 30: Material and Methods Tab. 4. Antibi
Page 31 and 32: Material and Methods Iron-free 5b m
Page 33 and 34: Material and Methods Solution3, car
Page 35 and 36: Material and Methods 3.6 Plasmids T
Page 37 and 38: Material and Methods PCR-Screening
Page 39 and 40: Material and Methods on ice for 10
Page 41 and 42: Material and Methods stained in eth
Page 43 and 44: Material and Methods 4.2.5.3 Conver
Page 45 and 46: Material and Methods 4.2.5.9 Ligati
Page 47 and 48: Material and Methods strains were s
Page 49 and 50: Material and Methods 9.5). For sign
Page 51 and 52: Material and Methods gentle shaking
Page 53 and 54: Material and Methods columns were w
Page 55 and 56: Results 5 Results 5.1 Analysis of s
Page 57 and 58: Results The 13-kb open reading fram
Page 59 and 60: Results If integration is due to a
Page 61 and 62: Results Yersiniabactin is a siderop
Page 63 and 64: Results Next, a large number of tra
Page 65 and 66: Results Nevertheless the site of tr
Page 67 and 68: Results Achr2_KpnI_rev binding site
Page 69 and 70: Results Interestingly the mutant Ps
Page 71 and 72: Results XAD4-purification yielded i
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Results After changing the mobile p
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Results P P A Fig. 21. Isoelectic f
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Results reduced in comparison to th
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Results A-E represents single inocu
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Results Tab. 10. Development of pop
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Results Tab. 11. Distribution of th
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Discussion bacteria with redundande
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Discussion 6.2 Possible regulation
Page 89 and 90:
Discussion stationary phase transit
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Discussion and bacterium (Loper et
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Literature Bultreys, A., Gheysen, I
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Literature Galperin, M. Y. (2006).
Page 97 and 98:
Literature Mazzola, M. (2002). Mech
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Literature Schubert, S., Rakin, A.,
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Literature Zou, J., Rodriguez-Zas,
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