1,

with outer wells filled with sterile H2O to minimize evaporation. Replicate plates were then covered but not sealed and incubated for 24 h at 28°C or 22°C with shaking. The next day cells were pelleted by centrifugation (4000 g, 15 min) and 150 μl of supernatant was transferred to fresh wells in a flat bottomed 96-well plate. To each well 30 μl of CAS dye (prepared as described above) was added using a multi channel pipette. Plates were immediately placed into the plate reader and OD 655 values recorded every 5 min for 50 min, then again at 65 min and 125 min. EDDHA Inhibitory Concentration (IC50) assays A 2-fold serial dilution series of KB media containing from 200-0.195 μg/ml of the iron chelator EDDHA (ethylene-diamine-di(o-hydroxyphenylacetic acid); STA-9090 a generous gift from Dr Iain Lamont) was established in 96 well plates. Strains were inoculated in quadruplicate to an initial OD 600 of 0.1 from cultures

synchronized by sub-inoculation over two nights, giving a final volume of 125 μl per well. Unsealed plates were then incubated for 24 h at 28°C or 22°C with shaking. Wells were diluted 1:1 with KB in order to be within the linear range of the plate reader, and OD KU-57788 in vitro 600 values were measured. For each temperature the assay was repeated twice with consistent results. Errors are presented as ± 1 standard deviation. P. syringae 1448a pathogenicity tests in Phaseolus vulgaris Single colonies from fresh 48 h KB agar plates were picked using a sterile hypodermic needle. Strains were then inoculated into snap bean pods (Phaseolus vulgaris) by piercing the surface of the bean approximately 5 mm. Each strain was inoculated in triplicate together with a WT positive control. Bean pods were then placed in a sealed humid containers or alternatively, for on plant assessment, pods were left attached to parental plants growing indoors at 20-25°C. Results were recorded every 24 h. Development of water soaked lesions similar to those of WT strain was taken as a positive result. The assay was repeated in triplicate. Acknowledgements

We are grateful to Professor John Mansfield (Imperial College, Fenbendazole London) for providing us with the strain of P. syringae 1448a that was the subject of this study as well as for his many helpful suggestions for working with this strain. We also thank Professor Iain Lamont (University of Otago, New Zealand) for his generous gift of EDDHA and for sharing his valuable time and advice. This work was supported by the Royal Society of New Zealand Marsden Fund [contract number VUW0901] and Victoria University of Wellington New Researcher and University Research Fund Grants to DFA. JGO was supported by a Victoria University of Wellington PhD Scholarship and subsequently by Marsden postdoctoral funding.