MEASUREMENT OF OXYGEN UPTAKE UNDER CONTROLLED PRESSURES OF CARBON DIOXIDE

QUANTITATIVE STUDIES OF THE EFFECT OF ORGANIC SUBSTRATES AND 2,4-DINITROPHENOL ON HETEROTROPHIC CARBON DIOXIDE FIXATION IN HYDROGENOMONAS FACILIS

McFadden, Bruce A. (Washington State University, Pullman), and H. Robert Homann. Quantitative studies of the effect of organic substrates and 2,4-dinitrophenol on heterotrophic carbon dioxide fixation in Hydrogenomonas facilis. J. Bacteriol. 86:971-977. 1963.-Whole cells of Hydrogenomonas facilis under heterotrophic conditions fixed levels of C(14)O(2) which depended upon the nature of the carbon source being oxidized. It was established that oxidative rates varied as a function of p(CO2). Therefore, all studies were conducted in the presence of 1.5 mole% CO(2) in the gas phase. With glucose-grown cells supplied with glucose as substrate, the heterotrophic fixation was curtailed 98% by the addition of 8.3 x 10(-4)m 2,4-dinitrophenol (DNP). A coupling between reductive fixation of CO(2) and heterotrophic oxidation of substrate is consistent with the observed effect of DNP. The efficiency of coupling of fixation with oxidation was studied for acetate, d-glucose, l-glutamate, d,l-lactate, d-ribose, and succinate as substrates. Kinetic studies showed that the efficiency of coupling (expressed as disintegrations per minute of C(14) per microliter of O(2)) was initially time-variable for all substrates; however, it approached a constant value after 30 to 45 min for acetate, glutamate, lactate, and succinate. The initial variation of the ratio with time was due primarily to C(14)O(2) uptake, which was nonlinear with time. Control studies in the absence of exogenous substrate indicated that CO(2) fixation may also be linked to oxidation of endogenous stores accumulated during heterotrophic growth. d-Ribose appears to be the most promising substrate for short-term fixation studies owing to the rapid incorporation of C(14) and the unusually low endogenous fixation rate by cells grown on ribose. Calculations reveal that, after isotopic equilibrium has occurred, the amount of CO(2) utilized during glucose oxidation is almost 50% of O(2) uptake during the same interval. Even during succinate oxidation, which was shown to be coupled much less effectively with CO(2) fixation, the CO(2) utilized during the same interval is 8% of O(2) uptake.

Radiorespirometric studies of carbohydrate metabolism by washed spermatozoa of various species

1. The patterns of 14CO2 evolution from specifically labeled glucose substrates by washed bull, ram, boar, rabbit, dog, rooster and turkey spermatozoa were similar and indicated the Embden-Meyerhof and Kreb's cycle pathways as the major route of energy metabolism. 2. Honey bee spermatozoa metabolized glucose-3,4-[14C], glucose-[U-14C] or fructose-[U-14C], but not glucose-1-[14C], glucose-2-[14C]or glucose-6-[14C], indicating the presence of the glycolytic pathway, but the absence of respiration via the Kreb's cycle. 3. The rate of glycolysis exceeded the rate of respiration in the spermatozoa of all the species studied. 4. A preferential utilization of glucose-1-[14C] over glucose-6-[14C] was evident in some sperm samples, but no consistent indication of pentose cycle metabolism was observed, due to considerable variability between samples within each group. 5. Fructose metabolism was greater than glucose metabolism in the rooster, less in the dog, boar and turkey, and similar in the spermatozoa from the other species examined. 6. Only ram and bull spermatozoa metabolized acetate-1-[14C] to any extent.

Revival of respiration and photosynthesis in dried leaves of Polypodium polypodioides

The leaves of the epiphytic fern Polypodium polypodioides, which lives on the branches of trees, are very similar to those of most higher plants except for the presence of scales on the dorsal side of the leaves. The structure of the cells of the chloroplasts and the mitochondria is the same as that of other higher plants. The only obvious difference found was that the contents of the central vacuole solidified when dehydrated. P. polypodioides was not damaged by loss of 97% of its normal water content and photosynthetic activity was found to be proportional to water content between 20 and 100% water content. When a dried leaf was immersed in liquid water, almost all of the original photosynthetic activity reappeared in the first 30 min of rehydration, provided incisions had been made into the leaf before drying.The rate of water uptake by intact (uncut) leaves was strongly inhibited by anaerobic conditions. This inhibition could be relieved by cutting the leaves, by supplying oxygen, or by removing the scales.Since in P. polypodioides the photosynthetic apparatus is not damaged by severe dehydration its quick revival does not depend on a special repair mechanism. Therefore, P. polypodioides should be a suitable object for a number of studies on the mechanism of photosynthesis.

[The light-induced synthesis of the NADP(+)-dependent glycerin-aldehyde-3-phosphate-dehydrogenase : III. The importance of chlorophyll and the influence of metabolic inhibitors]

1. A chlorophyll-less Pisum sativum mutant showed - in contrast to the normal form - no increase in the activity of the NADP(+)-dependent glycerinaldehyde-3-phosphate-dehydrogenase following illumination. 2. In both forms of Pisum the amount of the enzyme present in the dark was about equal. 3. DCMU, an inhibitor of the noncyclic electron flow in photosynthesis reduces the light-induced synthesis of the enzyme to about half in a concentration of 10(-6) m and inhibits it totally at higher concentrations. The dark values of enzyme activity were not influenced by the presence of the inhibitor. 4. Salicylaldoxime also blocks the enzyme synthesis in the light; this effect increases with increasing concentration of the inhibitor. The inhibition is complete at a concentration of 5 · 10(-4) m. 5. Sodium azide in a concentration of 10(-3) m inhibits the photosynthesis and the light-induced GPD-synthesis almost completely; respiration is diminished by more than 50% whereas the dark value of the GPD-activity remains unchanged. 6. 2,4-Dinitrophenol in a low concentration (10(-6) m) increased the oxygen consumption in the dark considerably, but the photosynthesis only slightly. The light synthesis of the enzyme was not affected, nor was the dark value influenced. At a concentration of 10(-5) m there was a slight decrease in respiration and a greater decrease in the photosynthesis. The dark value of the GPD was not different from that of the controls whereas the synthesis in the light was markedly diminished. A concentration of 10(-4) m completely blocks the respiration, the photosynthesis, and the light-induced GPD-synthesis; the dark value is decreased to about 50%. 7. It is concluded that the reversible synthesis of the NADP(+)-dependent GPD in light is dependent on chlorophyll and on an intact photosynthesis; the decisive reaction in this connection is the photoreaction II, the noncyclic electron flow.

Carbon Dioxide Effects on Glucose Catabolism by Mixed Microbial Cultures

Results have shown that, with mixed culture (sewage) inocula, the lag period in aerobic catabolism of glucose can be reduced by increased CO 2 tension. Conversely, removal of CO 2 from the air supply to the growth flasks and Warburg vessels may increase the lag period.

Respiration of Heart Muscle as Affected by Oxygen Tension

Isolated cat papillary muscles were exposed to gas mixtures containing carbon dioxide and oxygen. In muscles exposed during the second of three periods to 25 percent oxygen, the volume of oxygen consumed (Q(o2)) was depressed by 50 percent, but returned to the control level during a third period at 98 percent oxygen. The work capacity was not significantly altered if the partial pressure of oxygen was low.