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Leucothrix: Absence of Demonstrable Fixation of N2
Abstract
Summary: Leucothrix mucor Oersted is a common marine epiphyte, probably ubiquitous on shores around the world. The long, unbranched filaments, which are usually attached to algae, taper somewhat from 2 μm wide at the base to less than 1 μm wide at the distal end. Asexual reproduction is effected by the abstriction and detachment of terminal segments or single cells, which are capable of slow gliding on solid substrates until they re-attach. In liquid cultures, rosettes of shorter filaments are commonly formed. Although apochlorotic, and presumably an obligate heterotroph, Leucothrix shows certain resemblances to blue-green algae such as Calothrix. Unlike Calothrix, however, it apparently lacks heterocysts. In spite of this, its possible affinity with blue-green algae suggested that Leucothrix might be able to fix N2. This was tested by the acetylene reduction assay for nitrogenase activity (Stewart, Fitzgerald & Burris, 1967).
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© Society for General Microbiology, 1974