The following nine mutant strains of Neurospora crassa were used in these studies: E5212, C86, B1312, 39401, 10575, C83,E5029, 4540, and 3416.Each of these nine mutants is able to utilize one or more of the following compounds: quinic acid, tyrosine, phenylalanine, anthranilic acid, indole, tryptophane, o-N-formylkynurenine,kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic acid, and nicotinic acid.
Metabolic accumulations by four of the strains have beenstudied. The accumulation of anthranilic acid by mutant 10575 has been recognized for some time. It is now clear that this strain accumulates other highly fluorescent substances and at least oneother biologically active substance. Mutant C83 accumulates relatively large quantities of anthranilic acid, and an unidentifiedderivative of indole.Strain E5029 accumulates a compound, apparently anthranilic acid, with biological activity for strain B1312; unidentified39401-active and E5212-active substances; and kynurenicacid, which isbiologically inactive. Mutant E5212 accumulates anthranilic acid, nicotinic acid, and also a substance which is active for E5212 itself.
Evidence has been obtained which indicates that in Neurospora antranilic acid is a precursor of tryptophane, with indole as anintermediate between the two compounds; and also that tryptophane is degraded to anthranilic acid, with kynurenine as an intermediate.Thus a metabolic cycle involving anthranilic acid, indole, tryptophane, and kynurenine is clearly indicated.
Crosses involving mutants 39401 and C86 have furnished evidence that the mutation which prevents the growth of 39401 on minimal medium is the same as that which prevents the growth of C86 on minimal,and that a numberofmodifiers affect this primary mutation in such a way that off spring are produced which differ qualitatively ingrowth requirements fr om both C86 and 39401. Six modifiers havebeen postulated to explain the observed ascus segregations. In addition a suppressor of the primary mutation has been found. Possible mechanisms by which the modifiers exert their effects are considered briefly.
