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Enzymatic, lectin, and morphological characterization and classification of presumptive cyanobionts from Azolla Lam

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Summary

A number of cyanobacterial strains from the Azolla Lam. symbiosis, all independently isolated by different researchers, were simultaneously evaluated in order to document distinguishing traits. Ten presumptive secondary (minor) cyanobionts from Azolla were identified by genus and compared by morphology, binding to FITC-conjugated lectins, and enzyme electrophoresis. Identification of allozymes was particularly helpful in differentiating among strains. Anabaena variabilis ATCC 24413 and Anabaena sp. PCC 7120 served as the free-living control taxa. Based on morphological features, six strains identified as Anabaena and four as Nostoc. Those identified as Anabaena closely resembled one another morphologically and in general did not bind to lectins. In their banding patterns of 12 enzymes, five of the Anabaena cultures were identical to each other and to A. variabilis. No correlation was found between this group of cyanobaionts and any single Azolla host species. The Nostoc strains were each distinctive in appearance, and unrelated enzymatically. Cells of only one Nostoc, from India and judged to be an epiphyte rather than a symbiont, reacted with certain lectins (Canavalia, Erythrina, Phytolacca and Triticum). Culturable cyanobacteria from Azolla, previously asserted to be either Anabaena or Nostoc exclusively, have now been observed to belong to both genera.

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