Influence of phosphorus on physiology of a hair-forming blue-green alga (Calothrix parietina) from an upland stream

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Abstract
An axenic clonal strain of the blue-green alga Calothrix parietina, isolated from a stream where most of the soluble phosphate is known to be in the organic form, was used for physiological studies on the effects of phosphate deficiency and ability to use organic phosphates. Hairs were formed when the concentration of cellular phosphorus dropped to c. 10 μg P mg dry wt−1, a level well above the minimum (2.5 μg P mg dry wt−1) found in filaments which could still be regarded as relatively healthy. Inducible phosphatase activity commenced at about the same time as hair formation, and staining techniques showed that phosphomonoesterase activity occurred on the walls of hair cells and the adjacent chlorophyll-containing cells. The part of the sheath furthest from the heterocyst also showed marked activity. Tests with various substrates revealed both phosphodiesterase and phytase activity. The ability to use organic phosphorus substrates could be particularly important for this organism in its natural environment.