赤潮プランクトンのＢ群ビタミン要求に関する研究 ＩＩ Ｓｋｅｌｅｔｏｎｅｍａ ｃｏｓｔａｔｕｍ（ＧＲＥＶＩＬＬＥ）ＣＬＥＶＥ及びＥｕｔｒｅｐｔｉｅｌｌａ ｓｐ．のＢ群ビタミン要求に関する増殖生理

Abstract

The physiological growth characteristics of Skeletonema costatum (GREVILLE) CLEVE (Bacillario-phyeeae) and Eutreptieila sp. (Euglenophyceae), red tide phytoplanktons, were exzmined with special reference to B vitamin requirements in axenic batch cultures. S. costatum was found to be euryhaline, and its optimum growth was obtained at relatively low nitrate and phosphate concentrations. The maximum specific growth rate was 1.22 day-1. The alga required only vitamin B12 of Bvitamins tested for the growth:12ng/l to maintain maximum growth yields and 9.2×10-6pg to produce one cell. The vitamin B12 half-saturation wnstant was estinsated at 1.38ng/l. Eutreptiella sp. was found to be also euryhaline, and preferred relatively high concentrations of nutrient salts. The maximwn specific growth rates were 0.76-1.25 day-1. Vitamin B12 was essential for the growth and thiamine increased the peak population densities. Vitamin B12 half-saturation constants were 0.23ng/l (thiamine-added) and 1.05ng/l (thiamine-omitted). The vitamin B12 concentration necessary for maximization of growth yields was 10ng/l and that for production of one cell was 1.4×10-4pg. The peak population density grown without thiamine was 30% of the control level. The concentration of thiamine necessary for the normal growth was estimated at 0.2μg/l.