e. multi dimensional scaling, MDS). Such graphical analysis helped GS 1101 to identify exudate compounds and cultures which tended to cluster together and have high similarities. The cluster procedure was an average linking one, and all similarities used were based on Eucledian distances. Exudate compounds identified were scored ‘1’ for the presence, and ‘0’ for the absence of the compound. HPLC analysis of streptomycete secondary metabolites The chromatographic system consisted of a HP 1090 M liquid chromatograph equipped with a diode-array detector and HP Kayak XM 600 ChemStation (Agilent Technologies, Waldbronn, Germany). Multiple wavelength monitoring was performed at 210, 230, 260, 280, 310, 360, 435 and 500 nm, and UV-visible spectra
measured from 200 to 600 nm. Five-μl aliquots of the samples were injected onto a HPLC column (125×3 mm, guard column 20×3 mm) filled with 5-μm Nucleosil-100 C-18 (Maisch, Ammerbuch, Germany). The samples were analyzed by linear gradient elution using 0.1% ortho-phosphoric acid as solvent A and acetonitrile as solvent LY333531 mw B, at a flow rate of 0.85 ml min-1. The gradient was from 4.5% to 100% for solvent B in 15 min with a 3-min hold at 100% for solvent B. Evaluation was carried out by means of an in-house HPLC-UV–vis database which contains nearly 1000 reference compounds, mostly antibiotics . Electron microscopy The megagametophyte tissues were evaluated on those A. angustifolia seedlings, which showed interrupted cotyledon
connections. Samples were fixed in 0.05 M sodium phosphate buffer (pH 8.0) containing 2% glutaraldehyde. The samples were gradually dehydrated in acetone, critical-point dried, sputter-coated with gold and observed by scanning electron microscopy. Acknowledgements Sodium butyrate We gratefully acknowledge the help of Elisabeth Früh, Nadine Horlacher, Martin Galic, Martina Schmollinger, Kerri Hagemann, Sarah Bayer, and Silvia Schrey for help in sample acquisition, sample analysis, and helpful suggestions. We also appreciate the helpful suggestions by the reviewers. This work was supported by a DFG (Deutsche Forschungsgemeinschaft) grant to RH. References 1. Janzen DH: The future of tropical ecology. Ann Rev Ecol Syst 1988, 17:303–324.
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