Statistical Measurement of Biotin, Thiamine, and Zinc Concentrations Required for Maximal Growth of Arthrobotrys conoides1

Abstract

Brunswick, N.J.), WALDIMERO COSCARELLI, AND DAVID PRAMER. Statistical measurement of biotin, thiamine, and zinc concentrations required for maximal growth of Arthrobotrys conoides. Appl. Microbiol. 10:413-417. 1962.-An experiment of central composite design was performed to determine simultaneously the most suitable concentration of each of three nutrients essential for proliferation of the nematode-trapping fungus, Arthrobotrys conoides, and to detect any significant interaction that occurred when they were supplied at different levels. Regression analyses of the results obtained revealed that for maximal growth of A. conoides in a glucose-inorganic salts medium, biotin, thiamine, and zinc were required at concentrations of 5, 100, and 400 ,ug/liter, respectively. No interaction of significance was detected. The analytical procedures are presented in detail, and the benefits that accrue from a statistical approach are discussed. Elucidation of the nutritive requirements of a biological system consists of two principal aspects. These can be categorized as: identification of those factors essential for growth, and determination of concentrations necessary for maximal development. The present paper is concerned with the latter aspect only: specifically, the optimal concentrations of biotin, thiamine, and zinc which were demonstrated as required for growth of the nematodetrapping fungus, Arthrobotrys conoides, in a glucoseinorganic salts medium (Coscarelli and Pramer, 1962). Traditionally, in a study of this type, a series of experiments is conducted and each factor is varied in turn while holding all others constant. Although this is a valid method of investigation, too frequently it is not realized that the results obtained are applicable only under the specific conditions employed in the tests. Use of designed experiments, involving the simultaneous variation of more than