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SIGNIFICANCE OF BACTERIAL‐ ANABAENA (CYANOPHYCEAE) ASSOCIATIONS WITH RESPECT TO N 2 FIXATION IN FRESHWATER 1, 2
Author(s) -
Paerl Hans W.,
Kellar Penelope E.
Publication year - 1978
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.1978.tb00295.x
Subject(s) - biology , heterocyst , bacteria , nitrogenase , axenic , anabaena , cyanobacteria , algae , nitrogen fixation , photosynthesis , botany , anabaena variabilis , microbiology and biotechnology , biochemistry , genetics
The functional aspects of specific associations between bluegreen algae and bacteria were investigated using both naturally occurring and cultured species of Anabaena. In take waters where bacteria were associated with Anabaena heterocysls, the bacteria exhibited a chemotactic response to a variety of amino acids and glucose. Earlier autoradiographic evidence that bacteria associated with heterocysts incorporate identical substrates indicates that associated bacteria probably benefit by utilizing algal excretion products. In return, the bacteria stimulate algal N 2 fixation. The most likely mechanism explaining such stimulation appeared to be bacterial oxygen removal in microzones (< 3 μm diam) bordering heterocysts during periods of high ambient oxygen concentrations. In the presence of bacteria, Anabaena rapidly overcame nitrogenase‐ inhibiting concentrations of oxygen. Axenic cullures had more extensive nitrogenase inhibition, and took longer to recover in response to oxygenation. Algal‐bacterial mutualism aids Anabaena in maintaining concurrent optimal N2 fixation and high photosynthetic rates in highly oxygenated surface waters.