Studies on the Growth factors of an Axenic Clone of the Cyanobacterium Microcystis aeruginosa K-3A.

Abstract

To reveal growth characteristics of the cyanobacterium Microcystis, a dominant organism of the water bloom occurring in eutrophicated lakes, a survey was conducted on nutritional factors to promote or inhibit the growth of an axenic strain of M. aeruginosa K-3A isolated from Lake Kasumigaura.
A number of compounds such as metals. B-group vitamins, amino acids, purine and pyrimidine bases, organic nutrients, monosaccharides and organic acids were tested for the effects on the growth of the cyanobacterium. Among compounds tested, iron and vitamin B₁₂ were found to be effective factors to promote growth. Iron was essentially required, and FeSO₄ was the most available form of iron compounds tested. Vitamin B₁₂ increased 3- to 5-fold the maximum growth added at the concentration of 100μg·1^-1 The promotive effect of vitamin B₁₂ was able to be replaced by cobaltous sulfate. EDTA, a chelating agent which is usually supplied to the culture medium to accelerate the uptake of metals, was unnecessary and rather inhibitory for the growth.
Most organic compounds such as casamino acid, peptone, amino acids and monosaccharides were inhibitory. Several amino acids suppressed remakably the growth at the low concentration of less than 10 mg·1^-1.