Culture Medium for Enterobacteria

A new minimal medium for enterobacteria has been developed. It supports growth of Escherichia coli and Salmonella typhimurium at rates comparable to those of any of the traditional media that have high phosphate concentrations, but each of the macronutrients (phosphate, sulfate, and nitrogen) is present at a sufficiently low level to permit isotopic labeling. Buffering capacity is provided by an organic dipolar ion, morpholinopropane sulfonate, which has a desirable pK (7.2) and no apparent inhibitory effect on growth. The medium has been developed with the objectives of (i) providing reproducibility of chemical composition, (ii) meeting the experimentally determined nutritional needs of the cell, (iii) avoiding an unnecessary excess of the major ionic species, (iv) facilitating the adjustment of the levels of individual ionic species, both for isotopic labeling and for nutritional studies, (v) supplying a complete array of micronutrients, (vi) setting a particular ion as the crop-limiting factor when the carbon and energy source is in excess, and (vii) providing maximal convenience in the manufacture and storage of the medium.     

ISOLATION AND CHARACTERIZATION OF CHROMATIN FROM NEUROSPORA CRASSA

Different preparations of chromatin isolated from mycelia of Neurospora crassa were analyzed for DNA-associated RNA and proteins. The UV absorption spectra, the ultrastructure of chromatin, and the amino acid composition of the acid-extractable proteins were studied. The protein:DNA ratios range from 1.5 to 2.8; the RNA:DNA ratios range from 0.5 to 1.24. UV absorption shows a macimum at 259 mµ and a minimum at 238–239 mµ. The E280/E260 ranges from 0.59 to 0.70. Electron microscopy reveals a fibrous structure with individual fibers of 120–150 A average diameter. Attempts were made to study the protein by polyacrylamide gel electrophoresis and amino acid analysis. The results indicate that Neurospora chromatin does not contain basic proteins comparable to calf thymus histone. The ratios of basic to acidic amino acids range from 0.93 to 1.19. On electrophoresis, no bands are seen whose positions correspond to those of histones. Staining for basic proteins with fast green or eosin Y at pH 8.2 also shows a negative reaction, suggesting the absence of histones.     

Les tissus élaborateurs d'hormones stéroïdes chez les amphibiens urodèles

Résumé Les cellules du tissu glandulaire du testicule et de la glande interrénale de pleurodèle montrent les caractères généralement observés dans les cellules stéroïdogènes. Des différences existent entre les deux tissus. Le reticulum endoplasmique du tissu glandulaire est très développé et présent dans toutes les cellules qui sont d'aspect homogène. Au contraire, le tissu interrénal montre deux aspects cellulaires différents. Le premier se caractérise par un reticulum endoplasmique lisse relativement peu développé par rapport au tissu glandulaire, par des mitochondries petites et nombreuses, enfin par des liposomes denses et petits. Le deuxième aspect au contraire, se distingue par le petit nombre de mitochondries souvent géantes et à crêtes plus fréquemment organisées en faisceaux, par des liposomes nombreux de grandes dimensions et peu denses aux électrons.Le tissu glandulaire est très peu touché par l'hypophysectomie. Le reticulum persiste plusieurs mois comme d'ailleurs l'activité 5-3 -hydroxystéroïde deshydrogénase. Dans le tissu interrénal, la proportion des cellules d'aspects différents varie au profit des cellules à lipides abondants et à grandes mitochondries. L'activité 5-3 -hydroxystéroïde deshydrogénase est longtemps décelable.Le rôle du reticulum endoplasmique du tissu glandulaire est discuté en fonction des observations réalisées dans d'autres cellules stéroïdogènes à reticulum abondant. La signification des deux aspects cellulaires observés dans l'interrénale est discutée en relation avec les résultats expérimentaux obtenus en particulier chez le rat.Cette étude révèle que les critères d'activité d'une cellule stéroïdogène sont délicats à établir et doivent être différents d'un tissu à l'autre.

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Tissues secreting steroid hormones in urodele amphibians

Summary The fine structure of testis glandular tissue and interrenal gland cells of Pleurodeles shows the general features observed in other steroïdogenic cells. Certain differences exist between the two tissues. The agranular endoplasmic reticulum of the glandular tissue cells is well developed and present in all cells of similar appearance. On the contrary, the interrenal tissue cells show two different features. The first is characterised by a poorly developed smooth endoplasmic reticulum, compared with that of the glandular tissue, by small and numerous mitochondria, and finally by small electron dense lipid droplets. The second feature is the small number of mitochondria often giant and with fascicles of straight tubular cristae and numerous large lipid droplets of low electron density.The effect of hypophysectomy on the glandular tissue cells seem very slight. The endoplasmic reticulum and the 5-3 -hydroxysteroid dehydrogenase activity persists for several months. In the interrenal tissue, the proportions of the two different cellular features are modified. Cells rich in lipids and with large mitochondria are more abundant. It is possible to demonstrate a 5-3 -hydroxysteroid dehydrogenase activity for a long time after hypophysectomy. The functional significance of the agranular endoplasmic reticulum is discussed in relation to some other observations on different steroidogenic cells with a well developed agranular endoplasmic reticulum. The significance of the two cellular features observed in the interrenal gland is discussed in connection with experimental data obtained in the frog and the rat.This study shows that it is difficult to define criteria of cellular activity, which probably differ from one tissue to another.

Equipe de Recherche associée au C. N. R. S. Cytologie Ultrastructurale n 129.     

Isolation and characterization of glycolipids from some photosynthetic bacteria

Glycosyl glycerides have been found in substantial amounts in Chloropseudomonas ethylicum but could not be detected in two strains of Rhodopseudomonas palustris. Rhodospirillum molischianum possibly contains small amounts of monoglycosyl diglyceride. The glycolipids of C. ethylicum have been separated into two components. One of these, glycolipid I, is a monogalactosyl diglyceride. Glycolipid II, upon acid hydrolysis, yields galactose, rhamnose, and a third, unidentified sugar. The glycolipids or total lipids of the photosynthetic bacteria examined contained saturated and monounsaturated, but none of the more highly unsaturated, fatty acids.