Studies on the Nutrition of Fungi. Iv. Factors Influencing the Growth of Some Thiamin‐requiring Fungi

Abstract

bined and dried at 100°C. to constant weight. Thus each figure given in the following tables, unless otherwise stated, represents the composite weight of five cultures. The actual weight of mycelium obtained under controlled conditions has been made the criterion for the evaluation of the comparative effectiveness of various factors. However, it should be emphasized that biological phenomena cannot be reduced to mathematical figures without making a generous allowance for the frequent and often disconcerting fluctuations that characterize the behavior of living things. No matter how rigidly one may control the environmental conditions and repeat a given experiment, one will always find some differences in the weight of the crop. Even the different cultures of the same experiment made at the same time and under identical conditions will continue to vary. We have found that such variations may be from 5 to 10 per cent; 'however, this is not great enough to be significant. P ART I. THE EFFECT OF THE AGAR FACTOR.-Allyn and Baldwin (1932) found that agar-agar exerted a decisive influence on the growth of certain bacteria. They ascribe this beneficial effect to the fact that agar is a mild reducing agent. The present writers (1938) observed that a number of fungi made better growth on solid media than on nutrient solutions and assumed that some chemical factor was the cause.The following experiments were made to test the effect of small amounts of agar upon the yield of mycelium of several organisms. The medium used consisted of 2.5 per cent dextrose, 0.3 per cent amino acids, the inorganic salts, and three concentrations of thiamin: 1/20th, 1/100th, and 1/500th ppm. One set of each solution received 0.05 per cent agar, while the other was without agar (table 1). Table 1 shows that the increase was greatest in the presence of 1/20th ppm. thiamin and that it disappeared in all cases except one when the vitamin was reduced to 1/500thppm. Thus, the yield of Ph,ycomyces blckesleeanus was increased by 84 per cent when thiamin was added at the rate of 1/20th TABLE 1. The effect of agar on the yield of mycelium in mg. b!/ five fungi.THE NECESSITY of an extraneous supply of thiamin for the growth of many fungi has been definitely established, but we know comparatively little concerning the influence of a number of contributory factors upon the growth of such organisms. The present investigation is an attempt to extend our knowledge concerning these factors. Part I of this paper concerns itself with the agar factor; Part II with the effect of organic acids upon nitrogen utilization; and Part III with nitrogen-dextrose-thiamin ratio.TECHNIQuE.-Unless otherwise stated, all cultures were grown on 25 ml. of nutrient solution in Erlenmeyer flasks of 250. ml. capacity. The basic medium consisted of 0.5 gram each of ammonium nitrate, potassium dihydrogen phosphate, magnesium sulfate, 5 grams of Bacto-Dextrose of highest purity, 0.5 gram of a mixture of amino acids (d-arginine, d-glutamic acid, l-aspartic acid, 2 parts each, and 1 pa...

Morphological and Physiological Studies of Helicostylum piriforme Bainier

“…Among the amino acids tested glycine, alanine, arginine and glutamic acid supported good growth of the present fungus. These acids have generally been reported to be good sources of nitrogen for Mucorales by a number of authors (LOCKWOOD 1936, LEONIAN andLILLY 1940;LILLY 1956, RAIZADA 1957). The only amino acid whidi failed to induce satisfactory growth was histidine.…”

The Production of Penicillin in Surface Culture, using Chemically Defined Media

“…The stimulation of growth of Phycomyces blakesleeanus by the addition of organic acids to the medium had already been described by several groups of workers (e.g. Leonian & Lilly, 1940), while the Wisconsin workers mentioned above had already described their use for submerged cultures of Penicillium. Marloth (1931) had also shown that the addition of citrate to media containing sucrose increased the growth of two species of Penicillium.…”

The Effect of Glutamic Acid, Aspartic Acid, and Related Compounds on the Growth of Certain Tricholoma Species

“…On the other hand the amide had only a slight, positive efteet, eqnal to that of fnmarie acid after 35 days. The stimulative elfect of tartarie acid on fungal growth (Leonian and Lilly 1940), may he dne to its relatively close connection with the acids of the Krehs cycle. Therefore, its pre.sence in the ba.sal medium may possibly diminish the positive effect of the compounds added.…”

“…It was suggested, that the beneficial effect of these two dicarboxylic amino acids is bound up with their effect on the initial stages of growtb, at which stage ibey would he superior to every other amino acid, providing they have no toxic-effect on the organism and that there exists no complete helerolrophy which could prevent the synthesis of any particular amitio acid.However, since several organisms are ahle readily to form ghttamic acid hy reductive aniination of a-ketoglntaric acid, the stimulative effect of the dicarboxylic amino acids should not, perhaps, he ascribed to the amino acids as such hut to their carbon skeleton. As estahlished by Leonian and Lilly (1940), organic acids have a stimulative effect on fungal growth, and it seems not nnreasonahic l<( suppose that in the preseut case a-ketoglutaric, oxaloacetic, and probably other acids involved in the Krebs tricarhoxylic acid cycle could he effective as substittttes. Thus, the present study was undertaken in order to compare the growth effects of the two amino acids concerned, as well as of their corresponding keto-acids and fumaric acid.[584]…”