SOME FACTORS AFFECTING SEXUAL REPRODUCTION OF APHANOMYCES EUTEICHES

Papavizas , G. C, and C. B. Davey . (USDA, ARS, Crops Res. Div., Beltsville, Maryland.) Some factors affecting sexual reproduction of Aphanomyces euteiches. Amer. Jour. Bot. 47(10) : 884–889. Illus. 1960.—Oospores of Aphanomyces euteiches Drechsler were consistently formed in abundance on a medium (SM–2) consisting of mineral salts, D-glucose, thioglycolic acid, Difco “Special Agar-Noble,” and a mixture of amino acids added in proportions found in powdered yeast extract. The isolates of A. euteiches studied differed in their nutritional requirements for sexual reproduction. Isolates 4 and 7 formed oospores abundantly on SM–1 which was smiliar to SM–2 except that DL-glutamic acid was substituted for the amino acid mixture. Isolate 572 did not form oospores on medium SM–1 except when DL-methionine was substituted for thioglycolic acid. Sexual reproduction of isolates 4 and 7 was observed at a wider concentration range of reduced-sulfur-containing compounds than that of isolate 572. Sexual reproduction of the 3 isolates studied was influenced in a dissimilar way by varying concentrations of D-glucose and DL-glutamic acid, or by varying concentrations of D-glucose and of the amino acid mixture. The optimal sugar carbon/amino nitrogen ratio range for sexual reproduction of isolate 572 was about 5–22, whereas that of isolates 4 and 7 was 15–180. The pH range for sexual reproduction was as wide as that for growth. An acid reaction was more favorable than a neutral or alkaline one. The optimal pH range was 4.9–5.4. Vitamins were not essential.     

Ion transfer across lipid membranes in the presence of gramicidin A: I. Studies of the unit conductance channel

The conductance induced by gramicidin A in lipid bilayer membranes has been shown to be made up of discrete, well-defined units. In 0.1 M NaCl, and for 100 mV applied, the integral conductance of the unit channel at 20 °C is 5.8·10⁻¹² Ω⁻¹.     

Letter: crystallographic data fro lysoxyme from bacteriophage T4

The lysozyme of bacteriophage T4 has been crystallized in a form suitable for X-ray diffraction analysis. The space group is P3₁21 or enantiomorph, and the cell dimensions are $\text{a = b = 61.1}\text{A}\text{?}$, $\text{c = 96.3}\text{A}\text{?}$.