The influence of culture conditions on growth and sheath development of calcifying cyanobacteria

Calcifying cyanobacteria from the Everglades, Florida, USA, have been cultured in the laboratory. Nutrient concentration of the culture medium and illumination are of special importance for filaments physiologically and morphologically similar to the forms occurring in the natural habitat. High irradiance leads to a good development of an inner, pigmented, uncalcified sheath layer. When the cyano-bacteria grow in water supersaturated with respect to calcite, the outer sheath layers can be impregnated by carbonate crystals. The internal diameter of the resulting tube, however, depends on the-environmentally controlled-thickness of the uncalcified inner sheath.