津久井湖表層水におけるビタミンB12・チアミン・ビオチンの季節変化

概要

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Vitamin B12, thiamine and biotin concentrations in the surface water of Lake Tsukui have been determined over a period of two years, in 1970 and 1971, by the use of microbiollogical assay methods. The assay organism used for the determination of vitamin B12 was Lactobacillus leichmannii ATCC 7830, for thiamine was the marine yeast, Cryptococcus albidus, and for biotin the marine bacterium, Achromobacter sp. strain yH-51. Dissolved vitamin B12 concentration decreased remarkably and particulate portions increased considerably in the surface water at most times when diatoms, Cyclotella sp., Fragilaria crotonensis and Synedra acus, were dominant. Thiamine and biotin concetnrations increased very much in both dissolved and particulate forms in the surface water in such times when diatoms were dominant. From the results, the possible importance of vitamin B12 as one of the ecological factors in Lake Tsukui is suggested.