Abstract
Analysis of neutral and acidic ethyl acetate extracts from culture medium of Azospirillum brasilense 703Ebc by high-performance liquid chromatography (HPLC) and combined gas chromatography-mass spectrometry demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol, indole-3-methanol, and indole-3-lactic acid. IAA in media of 20 strains of A. brasilense and Azospirillum lipoferum was analyzed quantitatively by both the colorimetric Salkowski assay and HPLC-based isotopic dilution procedures. There was little correlation between the estimates obtained with the two procedures. For instance, the Salkowski assay suggested that the culture medium from A. brasilense 703Ebc contained 26.1 μg of IAA ml−1, whereas HPLC revealed the presence of only 0.5 μg of IAA ml−1. Equivalent estimates with A. brasilense 204Ed were 10.5 and 0.01 μg of IAA ml−1, respectively. The data demonstrate that the Salkowski assay is not a reliable method for measuring the IAA content of Azospirillum culture medium and that estimates in excess of 10 μg of IAA ml−1 should be viewed with particular caution. Metabolism of [2′-14C]IAA by A. brasilense 703Ebc yielded radiolabeled indole-3-methanol, whereas roots of maize (Zea mays L.) seedlings gave rise to [14C]oxindole-3-acetic acid and an array of polar metabolites. Metabolism of [2′-14C]IAA by maize roots inoculated with A. brasilense 703Ebc produced a metabolic profile characteristic of maize rather than Azospirillum species.
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Selected References
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- Döbereiner J., Baldani V. L. Selective infection of maize roots by streptomycin-resistant Azospirillum lipoferum and other bacteria. Can J Microbiol. 1979 Nov;25(11):1264–1269. doi: 10.1139/m79-199. [DOI] [PubMed] [Google Scholar]
- Ehmann A. The van urk-Salkowski reagent--a sensitive and specific chromogenic reagent for silica gel thin-layer chromatographic detection and identification of indole derivatives. J Chromatogr. 1977 Feb 11;132(2):267–276. doi: 10.1016/s0021-9673(00)89300-0. [DOI] [PubMed] [Google Scholar]
- Steensgaard J., Hill R. J. Separation and analysis of soluble immune complexes by rate-zonal ultracentrifugation. Anal Biochem. 1970 Apr;34(2):485–493. doi: 10.1016/0003-2697(70)90133-8. [DOI] [PubMed] [Google Scholar]
- Tien T. M., Gaskins M. H., Hubbell D. H. Plant Growth Substances Produced by Azospirillum brasilense and Their Effect on the Growth of Pearl Millet (Pennisetum americanum L.). Appl Environ Microbiol. 1979 May;37(5):1016–1024. doi: 10.1128/aem.37.5.1016-1024.1979. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Von Bülow J. F., Döbereiner J. Potential for nitrogen fixation in maize genotypes in Brazil. Proc Natl Acad Sci U S A. 1975 Jun;72(6):2389–2393. doi: 10.1073/pnas.72.6.2389. [DOI] [PMC free article] [PubMed] [Google Scholar]