FUNGI AS TEST ORGANISMS 223 



test substance present in the medium. Among the substances for which 

 quantitative assay procedures have been developed are the vitamins, 

 amino acids, and essential elements. Microorganisms have also been 

 used to discover pathways of biochemical synthesis and degradation, to 

 separate isomers, and for other analytical purposes. 



The essential features of a microbiological assay are (1) a suitable test 

 organism, (2) a suitable basal medium essentially free from the substance 

 under test, (3) preparation of the sample, (4) a reference standard (a 

 pure compound where possible), (5) two series of cultures to which a 

 known range of concentrations of the standard and unknown have been 

 added, (6) uniform inoculation, (7) incubation under uniform conditions, 

 (8) measuring the response of the test organisms, (9) construction of a 

 standard curve, and (10) calculating the results. 



When microbiological assay procedures are used, it is unnecessary to 

 isolate the compound being assayed from the other constituents present 

 in the sample. The preparation of the sample for assay is usually simple 

 and ordinarily involves hydrolysis. Microbiological procedures usually 

 require a short time to complete. The amount of sample needed is small, 

 which is an important consideration in some problems. Microbiological 

 assays are invaluable, provided that suitable test organisms are available, 

 in devising chemical procedures for the isolation of new vitamins and 

 other physiologically active compounds. 



Biochemical mutants of Neurospora and other fungi are particularly 

 useful in determining the pathways of synthesis of amino acids and other 

 compounds. 



REFERENCES 



Abrams, E.: Microbiological deterioration of organic materials, its prevention and 

 methods of test, Natl. Bur. Standards (U.S.), Misc. Pub. 188, 1948. 



Appling, J. W., E. K. Ratcliff, and L. E. Wise: Chemical and microbiological 

 differentiation of enantiomorphs of galactose and xylose, Anal. Chem. 19 : 496- 

 497, 1947. 



Atkin, L., W. L. Williams, A. S. Schultz, and C. N. Frey: Yeast microbiological 

 methods for determination of vitamins. Pantothenic acid, Ind. Eng. Chem., 

 Anal. Ed. 16: 67-71, 1944. 



AuERNHEiMER, A. H., L. J. WicKERHAM, and L. E. Schniepp: Quantitative deter- 

 mination of hemicellulose constituents by fermentation, Anal. Chem. 20: 

 876-877, 1948. 



Beadle, G. W. : An inositoUess mutant strain of Neurospora and its use in bioassays, 

 Joiir. Biol. Chem. 156 : 683-689, 1944. 



Beadle, G. W. : Biochemical genetics, Chem. Revs. 37 : 15-96, 1945. 



Beadle, G. W. : Genetics and metabolism in Neurospora, Physiol. Revs. 25 : 643-663, 

 1945a. 



Bonner, D.: Biochemical mutations in Neurospora, Cold Spring Harbor Symposia 

 Quant. Biol. 11 : 14-24, 1946. 



Brand, E., F. J. Ryan, and E. M. Diskant: Leucine content of proteins and food- 

 stuffs, Jour. Am. Chem. Soc. 67: 1532-1534, 1945. 



