The Effect of Magnesium Concentration on Growth of Chlorella

Abstract

A study of chlorophyll synthesis in Chlorella vulgaris (3) revealed striking differences in the growth patterns of this alga when cultured in nutrient solutions containing different amounts of magnesium. The differences in growth patterns were so variable and of such magnitude as to make difficult the finding of a suitable basis of comparison for physiological studies. Since Chlorella species are often the subject of such studies, a more exact knowledge of their growth habits seems desirable. The detailed studies of Chlorella made by PEARSALL and LoOSE (7) and MYERS (6) and numerous papers contributed by other workers have done much to advance the understanding of algal growth under various modifications of the culture conditions. This paper limits itself to comparisons of Chlorella growth at different magnesium concentrations. Data on certain aspects of this problem have been previously reported by SAIZEVA (9) and by VAN HILLE (5). Materials and methodsConical 500-ml. Pyrex flasks with sealed-in aeration tubes were autoclaved. Each flask was then filled with 350 ml. of sterile culture medium from a transfer flask in which as much as three liters of medium could be autoclaved in one batch (2). The full nutrient solution was prepared with reagent grade chemicals and contained the following components per liter of solution: KNO3, 10 m.mol.; Ca(NO3)2, 3 m.mol.; MgSO4, 2 m.mol.; KH2PO4, 2 m.mol.; ferric tartrate, 1 ml. of 0.5% solution; the micronutrients B, Mn, Zn, Cu, and Mo, in the amounts used by ARNON (1); glucose, 10 gm.; and Pyrex-redistilled water, to volume. The pH value of the autoclaved solution was 4 to 4.5. This solution was found to give consistently high culture densities, of the order of 200,000 cells per cu. mm. after a growth period of three weeks. In the media with lower magnesium contents, equivalent amounts of K2SO4 were substituted for the deficit in MgSO4. Glucose was supplied in the media in order to maintain a source of sugar for all cultures, whether or not they developed a chlorosis, and hence minimize the influence of starvation effects on cell growth.The magnesium concentrations used in these experiments were: 49 p.p.m. (full-magnesium), 2.8, 1.0, 0.5, and 0.2 p.p.m. Triplicate cultures of the first three concentrations were made; the latter two concentrations were run in

The Effect of Magnesium Concentration on Chlorophyll and Catalase Development in Chlorella

“…The Chlorella vulgaris strain previously described was used, and the data of the present paper were derived froin the same flask cultures, in fact from the same periodic samplings, as were reported in the preceding paper (5). The culture media contained glucose, and magnesium was present in the concentrations 0.2, 0.5, 1.0, 2.8, and 49 p.p.m., in replicate.…”

“…In both sets of curves, the sharp leveling off in the lower-magnesium cultures at approximately day 10 is probably due to the same cause-depletion of magnesium, resulting in-cessation of the reactions of chlorophyll formation and cell multiplication at this time. Both of these processes showed a vigorous revival when magnesium was added to the cultures (illus-trated in (5) for cell population). It should be stressed, however, that at the time when magnesium became limiting to chlorophyll synthesis, and to population increase, the synthesis of cell substance was still progressing at a rapid rate in these cultures (5).…”

“…Both of these processes showed a vigorous revival when magnesium was added to the cultures (illus-trated in (5) for cell population). It should be stressed, however, that at the time when magnesium became limiting to chlorophyll synthesis, and to population increase, the synthesis of cell substance was still progressing at a rapid rate in these cultures (5).…”

“…), and still less is required for synthesis of protein and other cell material contributing to cell enlargement. This suggested sequence is based only on the data presented here and previously (5), which are subject to the following limitations: (a) Catalase activity is measured, not its content. Changes in activity may not accurately reflect increases and decreases in the catalase iron-porphyrin content.…”

Manganese as Substitute for Magnesium During Magnesium-limited Growth of the Cyanobacterium Anacystis nidulans

“…Cell division could be one of the events where Mn2+ might substitute for Mg2+. Deprivation of either Mn2+ (Alberts-Dietert, 1941) or Mg2+ (Finkle & Appleman, 1953) resulted in cell enlargement of Chlorella, and cell enlargement was also found when a diatom was deprived of Mn2+ (Von Stosch, 1942).…”