Isolation and characterization of a marine Anabaena sp. capable of rapid growth on molecular nitrogen |
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Authors: | Gary Stacey Chase Van Baalen F Robert Tabita |
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Institution: | (1) Department of Microbiology, University of Texas at Austin, 78712 Austin, Tx, USA;(2) University of Texas Marine Science Laboratory, University of Texas at Austin, 78373 Port Aransas, Tx, USA |
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Abstract: | A marine filamentous cyanobacterium capable of rapid growth under N2-fixing conditions has been isolated from the Texas Gulf Coast. This organism appears to be an Anabaena sp. and has been given the strain designation CA. Cultures grown on mineral salts medium bubbled with 1% CO2-enriched air at 42°C show a growth rate of 5.6±0.1 generations per day with molecular nitrogen as the sole nitrogen source. This growth rate is higher than any other reported in the literature to date for heterocystous cyanobacteria growing on N2. Under similar growth conditions, 7.5 mM NH4Cl yields a growth rate of 6.6±0.1 generations per day while 7.5 mM KNO3 allows for a growth rate of 5.8±0.4 generations-day. Nitrogen-fixation rates, as measured by acetylene reduction, show maximum activity values in the range of 50–100 nmoles ethylene produced/minxmg protein. These values compare favorably with those obtained from heterotrophic bacteria and are much higher than values reported for other cyanobacteria. Growth experiments indicate that the organism requires relatively high levels of sodium and grows maximally at 42°C. Because of its high growth rate on N2, this newly isolated organism appears ideal for studying nitrogen metabolism and heterocyst development among the cyanobacteria. |
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Keywords: | Anabaena sp Nitrogen fixation Heterocysts Cyanobacteria Marine |
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