Possible evidence for novel metabolism of nitrogen gas by a green alga |
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Authors: | Pamela J Weathers James F Danielli Peter M Bradley Diane M Hebb Judith E Miller Rick L Pesano |
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Institution: | Dept of Biology and Biotechnology, Worcester Polytechnic Inst., Worcester, MA 01609, USA. |
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Abstract: | We report the isolation of a cukaryotic green alga ( Chlorella , strain WPI-2) which accumulates large stores of nitrogen (N) during growth in N-free medium and seems to incorporate14N2, yet does not reduce acetylene to ethylene. Total N accumulation during growth on N-free medium and in gases free of combined N was measured by three methods: Kjeldahl, oxidative pyrolysis via chemiluminescence (Antek N analyzer), and Dumas (Coleman N analyzer). Increases in N ranging from 22–64%± 1% were observed. Isotope dilution studies using cells labelled with 15NO 3- and then shifted to 14N2 in N-free medium showed dilution of the 15N isotope by 14N from 5.67 to 5.32%± 0.05%. Using a variety of conditions, we were unable to demonstrate the reduction of acctylene to ethylene by WPI-2, although diazotrophic cyanobacteria gave positive results. Although the data on WPI-2 are not conclusive in establishing this alga as a diazotroph, the data do suggest that within the Chlorophyceae there may exist a novel form of nitrogen gas metabolism. |
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Keywords: | Chlorella Chlorophyceae nitrogen metabolism |
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