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Utilization of carbon and nitrogen sources and acid/alkali production by cowpea rhizobia

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Sixteen slow-growing strains of rhizobia (15 cowpea rhizobia and oneR. japonicum) were examined to determine the effects of carbon and nitrogen sources on acid/alkali production in culture media. We found that the pH changes of the medium were more influenced by nitrogen sources than carbon sources (with the exception of ribose). When ammonium sulphate was used as a nitrogen source, all the cowpea rhizobia strains produced acid. When yeast-extract was used as a nitrogen source, however, a heterogenous pattern for acid/alkali production was found. The majority of the strains produced alkali from nitrate, glutamate and urea irrespective of carbon sources and acid from ribose irrespective of nitrogen sources.

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Correspondence to M. H. Ahmad.

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Ahmad, M.H., Smith, E. Utilization of carbon and nitrogen sources and acid/alkali production by cowpea rhizobia. Plant Soil 86, 279–282 (1985). https://doi.org/10.1007/BF02182904

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Key words

  • Cowpea rhizobia
  • Carbon source
  • Nitrogen source
  • Acid/alkali production
  • Ammonium sulphate
  • pH change