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Abstract
SUMMARY: Rubratoxin A or B can be assayed by overnight incubation at 25 °C of a standard inoculum of Tetrahymena pyriformis (Ehrenburg) strain w in nutrient medium containing differing toxin concentrations. Growth is estimated by measuring the extinction of the organism suspension after inactivation with Hayem’s fluid. The values obtained are expressed as a percentage of a normal control. Dose/res-ponse curves of percentage inactivation against log concentration of rubratoxin had linear ranges of 2·6 to 23 μg/ml for rubratoxin A and 8·5 to 30 μg/ml for rubratoxin B. The concentrations of toxin required to produce 50 % inhibition of growth in standard suspensions of T. pyriformis strain w were 8·75 μg/ml and 20·5 μg/ml respectively.
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© Society for General Microbiology, 1974