GROWTH OF MICROCYSTIS AERUGINOSA KÜTZ. IN A PRECIPITATE-FREE MEDIUM BUFFERED WITH TRIS

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Abstract
A dilute precipitate-free medium has been developed for the culture of Microcystis aeruginosa Kütz. With this medium, maximum growth rates of approximately 1.5 divisions per day have been attained during the first 3 days. Buffering between pH 7.4 and 7.7 with 10 mM tris (hydroxymethyl) aminomethane (TRIS) caused no toxicity. TRIS increased the tolerance of the alga towards supraoptimal concentrations of monovalent but not divalent cations. High concentrations of magnesium were toxic, but toxicity disappeared when magnesium: calcium ratios of 33:1 or lower were provided. An increase in nitrogen concentration caused no increase in yield, but a decrease caused a reduction. Doubling or halving the concentration of all other salts had no effect on yields. Growth in this medium was apparently limited by factors other than mineral nutrients. This alga has a rather low tolerance for potassium and requires little, if any, sodium.