microbioassay

mi·cro·bio·as·say .mī-krō-.bī-ō-'as-.ā, -a-'sā n bioassay in which the test organism is a microorganism

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mi·cro·bio·as·say (mi″kro-bi″o-asґa) the determination of minute quantities of an active substance or nutrient factor by a biologic method.