Interference with Deposition of Minerals in a Coccolithophorid Protozoon

Laboratory studies with axenic culture of the coccolithophorid,Hymenomonas MP 156, in chemically defined media have establishedthat this primitive protist deposits its minerals in essentiallythe same manner as multicellular organisms. An appreciable numberof inhibitors and natural compounds prevent deposition of mineralsin laboratory experiments. Among these cations other than Ca⁺²,certain amino acids, select intermediates of carbohydrate metabolism,and inhibitors of enzymes occupy a prominent place. Interferencewith deposition of minerals does not necessarily abolish proliferationof the coccolithophorid. However, electron-microscopic, autoradiographic,histological, and analytical studies of the various modes ofinterference reveal a profound alteration of organelles andphysiological activities. The ability of the protist to useits own extracellular, mineralized, calcareous structures asa source of Ca⁺² for growth under conditions of reduced cationsin the environment suggests a possible role for these microorganismsin cation equilibria of natural waters.     

The Inverse Relationship Between Nutrient Nitrogen Concentration and Coccolith Calcification in Cultures of the Coccolithophorid Hymenomonas sp.*

SYNOPSIS Chemical analysis of axenic cultures of Hymenomonas sp. reveals that the degree of coccolith calcification is inversely proportional to the concentration of available nitrogen sources in the medium. This relationship makes possible a useful degree of control over the organism's calcifying activities. In addition, a possible selective advantage of such a relationship in nature is suggested.     

Separation of Cytokinins from Danish Cabbage by Column Chromatography on Insoluble Polyvinylpyrrolidone

Chromatography of partially purified extracts of Danish cabbage (Brassica oleracea var. capitata L.) heads on polyvinylpyrrolidone columns using a weak phosphate buffer indicated a cytokinin complex containing nine components active in the modified Amaranthus betacyanin bioassay. Similar elution patterns were obtained with extracts of four different cabbage varieties but varietal differences occurred in the biological activity from each component peak. Paper and thin-layer chromatography indicated the presence of both zeatin and zeatin riboside in the extracts but the other cytokinin-active components were not identified. Separation of sweet-corn extracts by this technique indicated that most of the cytokinin activity occurred in the elution volume where zeatin and zeatin riboside would normally occur.