COMPARATIVE STUDIES ON RESPIRATION : X. TOXIC AND ANTAGONISTIC EFFECTS OF MAGNESIUM IN RELATION TO THE RESPIRATION OF BACILLUS SUBTILIS.

1. Concentrations of MgCl₂ up to 0.01 M have little effect upon the rate or respiration of Bacillus subtilis; at 0.03 M there is an increase in the rate, while in the higher concentrations there is a gradual decrease. 2. There is a well marked antagonism between MgCl₂ and NaCl, and a very slight antagonism between MgCl₂ and CaCl₂.     

COMPARATIVE STUDIES ON RESPIRATION : VIII. THE RESPIRATION OF BACILLUS SUBTILIS IN RELATION TO ANTAGONISM.

1. In relatively low concentrations of NaCl, KCl, and CaCl₂ the rate of respiration of Bacillus subtilis remains fairly constant for a period of several hours, while in the higher concentrations, there is a gradual decrease in the rate. 2. NaCl and KCl increase the rate of respiration of Bacillus subtilis somewhat at concentrations of 0.15 M and 0.2 M respectively; in sufficiently high concentrations they decrease the rate. CaCl₂ increases the rate of respiration of Bacillus subtilis at a concentration of 0.05 M and decreases the rate at somewhat higher concentrations. 3. The effects of salts upon respiration show a well marked antagonism between NaCl and CaCl₂, and between KCl and CaCl₂. The antagonism between NaCl and KCl is slight and the antagonism curve shows two maxima.     

SPORE GERMINATION AND CARBON METABOLISM IN FUSARIUM SOLANI. II. ENDOGENOUS RESPIRATION IN RELATION TO GERMINATION

Cochrane , V. W., Jean C. Cochrane , C. b . Collins , and F. G. Serafin . (Wesleyan U., Middletown, Conn.) Spore germination and carbon metabolism in Fusarium solani. II. Endogenous respiration in relation to germination. Amer. Jour. Bot. 50(8): 806–814. Illus. 1963.—Endogenous oxygen uptake by ungerminated macroconidia of Fusarium solani f. phaseoli is more than doubled by exogenous ammonium ion and is increased about 7-fold by germination. The respiratory quotient is halved by the provision of ammonia, which has essentially no effect on the endogenous formation of carbon dioxide. Stimulation by azide and 2,4-dinitrophenol suggests that the supply of phosphate acceptors regulates the rate of endogenous respiration. Mercurials poison the endogenous respiration, cyanide accelerates it, and iodoacetate, arsenite, fluoride, and chelating agents have little effect. Respiration is little affected by changes in pH, external phosphate, oxygen concentration, and spore density, within the limits tested. Spore lipid concentration is increased by cultivation in a high-glucose medium, but this variation in lipid content of spores docs not affect the endogenous Qo₂, nor does a high lipid content abolish the requirement for exogenous carbon for germination. Lipid utilization during endogenous respiration accounts for 37% of the loss in dry weight; lipid is also utilized during germination, but such utilization amounts to only about 5% of the carbon requirement. Neither mannitol nor nitrogenous compounds are significant substrates of endogenous respiration. The oxidation of the exogenous substrates tested does not measurably affect the concomitant rate of endogenous respiration. It is proposed that endogenous respiration can contribute to the synthetic processes of spore germination, although quantitatively insufficient to support germination without exogenous carbon. It is also questioned whether the respiratory quotient is an adequate index of the substrate of endogenous respiration.     

COMPARATIVE STUDIES ON RESPIRATION : XXVII. THE MECHANISM OF OXIDATION IN RELATION TO CHLOROFORM ANESTHESIA.

A mathematical analysis of the effects of chloroform on the production of carbon dioxide by living Ulva, killed Ulva, and unsaturated organic acids indicates that the same process is taking place in all three cases. On the basis of this interpretation it is reasonable to conclude that the action of chloroform on the oxidative mechanism of the cell is chemical in nature and that it acts either by catalysis or by the formation of a loose compound with some portion of the system.     

INTERMEDIATES IN THE METABOLISM OF STEROIDS BY PENICILLIUM LILACINUM.

Sebek, Oldrich K. (The Upjohn Company, Kalamazoo, Mich.), Lester M. Reineke, and Durey H. Peterson. Intermediates in the metabolism of steroids by Penicillium lilacinum. J. Bacteriol. 83:1327-1331. 1962-Nonproliferating cells of Penicillium lilacinum (Thom) metabolized progesterone successively to 20-beta-hydroxy-4-pregnen-3-one, testosterone, androstenedione, and testololactone. Testosterone and androstenedione were readily interconvertible. 11-alpha-Hydroxyprogesterone was transformed in an analogous way and its intermediate, 11-alpha, 20-beta-dihydroxy-4-pregnen-3-one, was isolated and identified by a combination of microbiological and chemical methods.     

COMPARATIVE STUDIES ON RESPIRATION : XI. THE EFFECT OF HYDROGEN ION CONCENTRATION ON THE RESPIRATION OF PENICILLIUM CHRYSOGENUM.

1. Variations in pH value between 4 and 8 produce practically no effect on the normal rate of respiration (the rate at neutrality is called normal). 2. Increasing the pH value to 8.80 causes respiration to fall to 60 per cent of the normal, after which it remains stationary for the duration of the experiment. 3. Decreasing the pH value to 2.65 causes a gradual rise and a gradual return to normal; at pH 1.10 to 1.95 the preliminary rise amounts to 20 per cent and is followed by a fall to below the normal. 4. The decrease in respiration brought about by solutions of a pH value of 1.95 or less are irreversible, while a similar decrease which occurs at pH 8.80 is reversible, the rate coming back to practically normal after the material is replaced in a neutral solution. 5. Determinations by means of Winkler''s method showed an increase in the consumption of oxygen in acid solutions and a decrease in alkaline solutions.     

COMPARATIVE EFFECTS OF ORGANIC AND INORGANIC MERCURY ON BRAIN SLICE RESPIRATION AND METABOLISM

—Respiration and carbohydrate metabolism were measured in guinea-pig brain slices exposed to organic and inorganic mercury. Organic mercury decreased oxygen uptake and ¹⁴CO₂ production at consistently lower concentrations than inorganic mercury. Organic mercury also caused a striking elevation of pyruvate and lactate at low doses where inorganic mercury had no effect on respiration or metabolism. A unique inhibition of tricarboxylic acid cycle function is suggested and might partially explain the distinctive neurotoxicity of organic mercury.     

STUDIES ON THE METABOLISM OF AUTOTROPHIC BACTERIA : I. THE RESPIRATION OF THIOBACILLUS THIOOXIDANS ON SULFUR

The data of this paper indicate that: 1. The "energy of activation" (µ) of sulfur oxidation by the autotrophic bacterium, Thiobacillus thiooxidans, is similar to that of other respirations. 2. The pH of the menstruum does not influence the respiration on sulfur between the limits of pH 2 to 4.8 once contact between the bacterial cell and the sulfur particle has been established but it does influence the rate at which such contact occurs. 3. The pO₂ has little effect upon the respiration of this organism. 4. Most organic materials have no detectable effect upon the respiration of Thiobacillus thiooxidans, but the organic acids of terminal respiration seem to stimulate the respiration in the absence of oxidizable sulfur and certain of them inhibit sulfur oxidation. 5. In so far as inhibitor studies on intact cells are trustworthy, sulfur oxidation goes through iron-containing systems similar to cytochrome. It is possible that the oxygen contained in the sulfuric acid formed during sulfur oxidation is derived from the oxygen of the water.