Observations on the Vitamin Requirements of Stereum frustulosum (Pers.) Fr.

Abstract

In a previous publication the senior author (1938) reported that Stereum frustulosum requires thiamin as an accessory growth substance. The present paper concerns further studies on the vitamin nutrition of this fungus. This investigation deals with the optimal dosage of thiamin, the action of the thiamin components (pyrimidine and thiazole), and the effects of the vitamins riboflavin, pyridoxine, and biotin. In addition, the effect of yeast extract and that of small amounts of a!gar was studied. The procedure and the basal medium employed in this investigation were essentially the same as those used by Fries (1938) in his extensive studies on the nutrition of wood destroying fungi. The ingredients of the medium were as follows: ammonium tartrate, M/10; sucrose, M!5; potassium phosphate, M/20; magnesium sulphate, M/100; ferric chloride, trace; distilled water was used to obtain the desired dilutions. The basal medium was used alone and with various vitamins or vitamin containing supplements. The culture medium was dispensed in 125 ml. Erlenmeyer flasks at the rate of 25 ml. per flask, sterilized in an autoclave, cooled and inoculated by mycelial transfer through the use of small (2 mm. x 2 mm.) hyphae-containing agar cylinders cut from the matgin of inoculum cultures grown in Petri dishes. The experimental cultures were then incubated for four weeks at 250C, collected on weighed filters, and the dry weights of the cultures were then determined in accordance with the usual gravimetric procedure. The production of dry matter was used as the criterion for the response to the vitamin supplements. The mean weight for each series of ten replicates was determined and the probable error was then calculated according to the directions given by Sherman (1941). The significance of differences between various means was ascertained by calculating the ratio between the difference between means and the probable error of the difference. The difference between two means was considered highly significant when the above ratio equaled or exceeded 3.5. This value means that the chances are 100:1 that the difference between the means is a real one and not one due to sampling error. The mean dry weights of the cultures together with the probable errors are presented in Table 1. The ritios of the differences between certain means divided by the probable error of the difference are presented in Table 2. The data in these tables show that thiamin brings about a significant increase in dry matter production (compare series 1 and 3 in Table 1). The difference between the two means is four times greater than the probable error of the difference, and the chances are therefore 142 to 1 that the observed dif-