The sulfonamide-requiring mutant of Neurospora: threonine-methionine antagonism.
نویسنده
چکیده
It has previously been reported (Emerson and Cushing, 1946; Emerson, 1947) that the so-called sulfonamide-requiring mutant strain of Neurospora (strain E-15172, hereafter designated by the symbol "sfo") does not grow on minimal medium at 35 C, that the addition of sulfanilamide (SA) permits maximum growth at that temperature and augments the growth occurring at lower temperatures, and that the SA-dependent growth is competitively inhibited by p-aminobenzoic acid (PABA). It was further shown (Zalokar, 1948) that the failure of this strain to grow at higher temperatures is due to inhibition by the amounts of PABA normally produced and that the growth-stimulating action of SA results from an antagonism of this inhibition. The sfo mutant was combined with a mutant (1633, designated "pab") that is unable to synthesize PABA, so that the amount of this vitamin available to the mycelium could be controlled by adding known amounts to the medium. The double mutant (sfo, pab) grows maximally on low concentrations of PABA and is inhibited strongly by slightly higher concentrations, which are still 100,000-fold less than are required to inhibit the wild type. Growth inhibition by the higher concentrations of PABA is competitively antagonized by SA. The present paper reports experiments that partially identify the reaction responsible for the sulfonamide-requiring character. From studies previously reported it has been supposed that there is a gene-controlled deleterious reaction (in sfo strains) that requires relatively higher levels of PABA than are needed for other PABA-dependent metabolic reactions. The present studies show that the deleterious reaction also requires somewhat more methionine (or homocysteine) than the minimum required for normal growth and that the inhibition resulting from excess methionine is competitively antagonized by threonine (or homoserine).
منابع مشابه
Effect of canavanine on mutants of Neurospora and Bacillus subtilis.
The inhibition of microorganisms by canavanine, an amino acid whi -1 occurs in the jack and horse beans (1, 2), has recently been the subject of several investigations. Horowitz and Srb (3) studied the effect of canavanine on three wild type strains of Neurospora, one sensitive, one of intermediate sensitivity, and one resistant to canavanine inhibition. They found that arginine and, to a lesse...
متن کاملMethionine synthesis in Neurospora crassa.
Horowitz and co-workers (Horowitz, 1947; Teas, Horowitz & Fling, 1948; Fling & Horowitz, 1951) have determined the pathway of methionine synthesis in Neurospora crassa, from genetic analysis of methionine-requiring mutant strains; it involves conversion of cysteine, via cystathionine, into homocysteine, which is methylated to methionine. A similar scheme has been suggested for methionine synthe...
متن کاملThe effects of canavanine, arginine, and related compounds on the growth of bacteria.
The physiological properties of canavanine, a naturally occurring, structural analogue of arginine, have not been extensively investigated. Recently, Horowitz and Srb (1) found that canavanine inhibited growth of wild type Neurospora, and that the inhibition was competitively alleviated by arginine. Lysine and methionine were also effective in alleviating canavanine inhibition for certain strai...
متن کاملStudies on the Nature of Resistance of Gram-negative Bacilli to Penicillin
The susceptibility of E. coli and Salmonella to penicillin is highest in a basal medium devoid of amino acids. Blood serum in certain concentrations, meat infusion broth, yeast extract, and casein hydrolysate interfere with the penicillin activity. The effect is apparently due to the antagonism of certain amino acids in the materials. Dicarboxyl-monoamino acids (i.e. aspartic, glutamic, and hyd...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Journal of bacteriology
دوره 60 2 شماره
صفحات -
تاریخ انتشار 1950