共查询到20条相似文献,搜索用时 15 毫秒
1.
1. Chloroform in low concentration (0.25 per cent) causes an increase in the rate of production of CO 2 in Ulva; this is followed by a decrease. In higher concentration (0.5 per cent) only a decrease is observed. 2. Assuming that the normal oxidation depends on the action of peroxide and peroxidase, experiments were made by placing Ulva in 1.0 per cent H 2O 2 and in Fe 2(SO 4) 3 (which acts like a peroxidase). The former diminishes the rate, the latter increases and subsequently decreases it. 3. When Ulva is killed in such a manner as to destroy the oxidizing enzymes, no CO 2 is produced unless H 2O 2 and Fe 2(SO 4) 3 are present. If to this mixture chloroform is added, the effect depends on the concentration of the iron. If the concentration is low there is an increase in the production of CO 2 followed by a decrease. If the concentration is high the rate appears to decrease from the start. 相似文献
2.
By means of a modification of the technique of the Osterhout apparatus it is possible to follow the production of CO 2 from sodium lactate when acted upon by H 2O 2. The results of this process indicate that the reaction is not a simple one but is of an autocatalytic type. This conclusion is borne out by the fact that the determinations of H 2O 2 during the reaction show an increased amount of peroxide during the earlier stages of the reaction. This is considered to be due to the formation of a peroxide by the oxidation of the acetaldehyde (formed by the interaction of H 2O 2 and sodium lactate) with the oxygen of the air. When the reaction is carried out in an atmosphere of nitrogen no increase is observed. Further experiments in nitrogen tend to show that acetaldehyde is the end-product of the action of H 2O 2 alone. The effect of FeCl 3 upon the reaction depends upon the previous treatment of the iron salt. If the iron solution is added to the H 2O 2 before mixing with the lactate there is an increased amount of CO 2. If, however, the iron is added to the lactate before the addition of the peroxide, the action tends to inhibit the production of CO 2. The reaction of H 2O 2 with sodium lactate is comparable to the action of killed yeast and methylene blue as determined by Palladin and his coworkers. 相似文献
3.
1. Organic acids when treated with H 2O 2 and Fe 2(SO 4) 3 produce CO 2 at a rate that can be measured by the indicator method. 2. In the case of acids containing a double bond, the rate of production of CO 2 can be varied by the addition of an anesthetic. The changes in the rate of production of CO 2 under the influence of a typical anesthetic, such as chloroform, show a striking resemblance to the reaction of the organism. 相似文献
5.
To evaluate the relative significance of CO 2-fixing enzymes in the metabolism of rat brain, the subcellular distribution of pyruvate carboxylase, phosphoenolpyruvate carboxykinase, NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase, as well as the fixation of H 14CO 3? by the cytosol and the mitochondria was investigated. Pyruvate carboxylase and phosphoenol-pyruvate carboxykinase are mainly localized in the mitochondria whereas NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase are present in both the cytosol and the mitochondria. In the presence of pyruvate rat brain mitochondria fixed H 14CO 3? at a rate of about 170 nmol/g of tissue/min whereas these organelles fixed negligible amounts of H 14CO 3? in the presence of α-ketoglutarate or phosphoenolpyruvate. Rat brain cortex slices fixed H 14CO 3? at a rate of about 7 nmol/g of tissue/min and it was increased by two-fold when pyruvate was added to the incubation medium. The carboxylation of α-ketoglutarate and pyruvate by the reversal of the cytosolic NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase respectively was very low as compared to that by pyruvate carboxylase. The rate of carboxylation reaction of both NADP-isocitrate dehydrogenase and NADP-malate dehydrogenase was only about 1/10th of that of decarboxylation reaction of the same enzyme. It is suggested that under physiological conditions these two enzymes do not play a significant role in CO 2-fixation in the brain. In rat brain cytosol, citrate is largely metabolized to α-ketoglutarate by a sequential action of aconitate hydratase and NADP-isocitrate dehydrogenase. The operation of the citrate-cleavage pathway in rat brain cytosol is demonstrated. The data show that among four CO 2-fixing enzymes, pyruvate carboxylase, an anaplerotic enzyme, plays the major role in CO 2-fixation in the brain. 相似文献
6.
Helicobacter pylori uses natural competence and homologous recombination to adapt to the dynamic environment of the stomach mucosa and maintain chronic colonization. Although H. pylori competence is constitutive, its rate of transformation is variable, and little is known about factors that influence it. To examine this, we first determined the transformation efficiency of H. pylori strains under low O 2 (5% O 2, 7.6% CO 2, 7.6% H 2) and high O 2 (15% O 2, 2.9% CO 2, 2.9% H 2) conditions using DNA containing an antibiotic resistance marker. H. pylori transformation efficiency was 6- to 32-fold greater under high O 2 tension, which was robust across different H. pylori strains, genetic loci, and bacterial growth phases. Since changing the O 2 concentration for these initial experiments also changed the concentrations of CO 2 and H 2, transformations were repeated under conditions where O 2, CO 2, and H 2 were each varied individually. The results showed that the increase in transformation efficiency under high O 2 was largely due to a decrease in CO 2. An increase in pH similar to that caused by low CO 2 was also sufficient to increase transformation efficiency. These results have implications for the physiology of H. pylori in the gastric environment, and they provide optimized conditions for the laboratory construction of H. pylori mutants using natural transformation. 相似文献
7.
1. The effects of O 2, CO 2, and pressure were studied in two very different species of protozoa, a flagellate, Chilomonas paramecium, grown in acetate-ammonium solution and a ciliate, Tetrahymena geleii, grown in 2 per cent proteose-peptone solution. 2. Chilomonas and Tetrahymena live and reproduce in solutions exposed to a wide range of O 2 concentrations, but Chilomonas is killed at high O 2 tensions in which Tetrahymena grows best. The optimum O 2 concentration for Chilomonas is about 75 mm. pressure but it lives and reproduces in O 2 tensions as low as 0.5 mm. while Tetrahymena fails to grow in concentrations below 10 mm. O 2 pressure. 3. With a constant O 2 tension of 50 mm. pressure, it was found that there is no significant variation in growth in Chilomonas between 50 mm. and 740 mm. total pressure. In Tetrahymena, however, under the same conditions, an optimum total pressure was found at about 500 mm. and growth is comparatively poor at 50 mm. total pressure. 4. Tetrahymena does not live very long in CO 2 tensions over 122 mm., although Chilomonas grows as well at 400 mm. CO 2 as in air at atmospheric pressure (0.2 mm. CO 2). Tetrahymena grows best in an environment minus CO 2, but the optimum for Chilomonas is 100 mm. CO 2 at which pressure an average of 668,600 ± 30,000 organisms per ml. was produced (temperature, 25 ± 1° C.). 5. Chilomonads grown in high CO 2 concentrations ( e.g., 122 mm.) produce larger starch granules and more starch than those grown in ordinary air at atmospheric pressure. 6. In solutions exposed to 75 mm. O 2 tension (optimum) and 122 mm. CO 2 plus 540 mm. N 2 pressure, chilomonads contain very little, if any, fat. This phenomenon seems to be due to the action of CO 2 on the mechanisms concerned with fat production. 7. In Tetrahymena exposed to pure O 2, there is very little fat compared to those grown in atmospheric air. This may be due to the greater oxidation of fat in the higher O 2 concentrations. 8. Further evidence is presented in support of the contention that Chilomonas utilizes CO 2 in the production of starch. 相似文献
8.
A sensitive assay based upon fluorescence of scopoletin allowed continuous recording of H 2O 2 production in illuminated intact cells of Anacytis nidulans. Onset of illumination was followed by a 5 to 10 second lag, a burst of very rapid production continuing for up to 5 minutes, and finally a slow and continuing steady rate of H 2O 2 production. Size of the H 2O 2 burst was decreased by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, by low O 2, and by certain Calvin cycle intermediates; it was increased by high light intensity, CO 2 depletion, Calvin cycle inhibitors (as iodoacetamide), cold shock, carbonyl cyanide m-chlorophenylhydrazone, and certain organic acids as glycolate). The H 2O 2 burst was explained by the following hypothesis: a low potential reductant is produced more rapidly than it can be used in the normal pathway to CO 2 reduction and, instead, reacts with oxygen. H 2O 2 production is regarded as a metabolic defect observable in Anacystis most dramatically during the transition from a very low rate of oxidative dark metabolism to a high rate of photosynthetic metabolism. 相似文献
9.
The oxyhydrogen reaction in the presence and absence of CO 2 was studied in H 2-adapted Scenedesmus obliquus by monitoring the initial rates of H 2, O 2, and 14CO 2 uptake and the effect of inhibitors on these rates with gas-sensing electrodes and isotopic techniques. In the presence of 0.02 atmosphere O 2, the pH 2 was varied from 0 to 1 atmosphere. Whereas the rate of O 2 uptake increased by only 30%, the rate of H 2 uptake increased severalfold over the range of pH 2 values. At 0.1 atmosphere H 2 and 0.02 atmosphere O 2, rates for H 2 and O 2 uptake were between 15 and 25 micromoles per milligram chlorophyll per hour. As the pH 2 was changed from 0 to 1 atmosphere, the quotient H 2:O 2 changed from 0 to roughly 2. This change may reflect the competition between H 2 and the endogenous respiratory electron donors. Respiration in the presence of glucose and acetate was also competitive with H 2 uptake. KCN inhibited equally respiration (O 2 uptake in the absence of H 2) and the oxyhydrogen reaction in the presence and absence of CO 2. The uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone accelerated the rate of respiration and the oxyhydrogen reaction to a similar extent. It was concluded that the oxyhydrogen reaction both in the presence and absence of CO 2 has properties in common with components of respiration and photosynthesis. Participation of these two processes in the oxyhydrogen reaction would require a closely linked shuttle between mitochondrion and chloroplast. 相似文献
10.
Measurements of CO 2 exchange at varying O 2 concentrations in seven grass species of the Laxa group of Panicum and activities of five photosynthetic enzymes were compared to values obtained for these characters in a cool season C 3 grass, tall fescue ( Festuca arundinacea Schreb.) and a C 4 grass, P. maximum Jacq. Plants were divided into three groups on the basis of the inhibition of apparent photosynthesis by 21% O 2. Rates of apparent photosynthesis in P. prionitis Griseb. and P. maximum were virtually unaffected by changes in O 2 concentration. In another group consisting of P. hylaeicum Mez., P. rivulare Trin., P. laxum Sw., and tall fescue apparent photosynthesis was inhibited by 28.2 to 36.0% at 21% O 2. An intermediate inhibition of 20.6 to 23.3% at 21% O 2 was exhibited by P. milioides Nees ex Trin., P. schenckii Hack., and P. decipiens Nees ex Trin. The CO 2 compensation concentration for P. prionitis and P. maximum was low (≤6 microliters per liter CO 2 at 21% O 2) and affected little by O 2, whereas values for P. hylaeicum, P. rivulare, P. laxum, and tall fescue were much greater, and increased almost linearly from 2 to 48% O 2. Values for P. milioides, P. schenckii, and P. decipiens were intermediate to the other two groups. The effect of O 2 on total leaf conductance to CO 2 was similar to the C 3 grasses and the intermediate Panicums. However, estimates of photorespiration in the intermediate species were low and changed little with O 2 in comparison to estimates for the C 3 species which were higher and increased greatly with increased O 2. 相似文献
11.
When leaf discs of Xanthium strumarium L. and Salvia splendens L. are incubated in sealed flasks in the light, more C 2H 4 gas is released in the presence of added CO 2 (30-200 millimolar NaHCO 3) than without CO 2. In Salvia, the maximum rate of C 2H 4 release occurs when sufficient CO 2 (above 125 millimolar NaHCO 3) is added to saturate photosynthesis confirming previous studies. The maximum rate of C 2H 4 release from illuminated discs is similar to the rate in the dark with or without CO 2 in both species. Glycolate enhances a CO 2-dependent C 2H 4 evolution from illuminated leaf discs. However, the maximum rate of C 2H 4 release with glycolate is the same as that observed with saturating CO 2. When photosynthesis is inhibited by darkness or by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, glycolate has no effect. Studies with [2,3-14C]-1-aminocyclopropane-1-carboxylic acid (ACC) show that the pattern of C2H4 release and the specific activity of the 14C2H4 in the presence and absence of glycolate is similar to that described above, indicating that glycolate does not alter uptake of the exogenously supplied precursor (ACC) or stimulate C2H4 release from an endogenous source at appreciable rates. Glycolate oxidase in vitro generates H2O2 which stimulates a slow breakdown of ACC to C2H4, but since exogenous glycolate is oxidized to CO2 in both the light and the dark it is argued that the glycolate-dependent increase in C2H4 release from illuminated leaf discs is not mediated directly by the action of enzymes of glycolate catabolism. The effects of glycolate and CO2 are not easily explained by changes in stomatal resistance. The data support the view that glycolate decarboxylation at subsaturating levels of CO2 in the light stimulates C2H4 release by raising the CO2 level in the tissue. 相似文献
12.
CO 2 fixation by a hydrogen-oxidizing bacterium, Cupriavidus necator, was evaluated in a packed bed bioreactor under a constant flow rate of gas mixtures (H 2, O 2, CO 2). The overall energy efficiency depends on the efficiencies of CO 2 fixation into carbohydrate and the reduced carbon into biomass and bioproducts, respectively. The efficiencies varied with the limiting gas substrate. Under O 2 limitation, the efficiency (20–30%) of CO 2 fixation increased with time and was higher than the overall efficiency (12–18%). Under H 2 limitation, the efficiency of CO 2 fixation declined with time while the biomass yield was quite similar to that under O 2 limitation. A cellular metabolic model was suggested for the lithoautotrophic growth of C. necator, including CO 2 fixation into carbohydrate followed by the main metabolic pathway of reduced carbon. Under CO 2 limitation, most H 2 energy was wasted, resulting in a very low biomass yield. Under a dual limitation of O 2 and nitrogen, biosynthesis of poly(3-hydroxybutyrate) was triggered, and the energy efficiency or yield of biopolyester was lower than those of microbial cell mass. Compared with a green microalga Neochloris oleoabundans that produces lipid under nutrient limitation, C. necator exhibited a much higher (3–6 times) energy efficiency in producing biomass and bioproducts from CO 2. 相似文献
13.
1. The effect of H 2 tension, CO 2 tension, pH, time, light intensity, density of suspension, salt content of the medium, and certain spectral regions on the rate of photoassimilation of H 2 and CO 2 by Streptococcus varians has been studied. 2. The method of making light absorption measurements with thin suspensions of bacteria is described. 3. A light source, optical system, and filter for isolating 852 mµ with 894 mµ in sufficient intensity for photochemical work and an improved design of thermostat are given. 4. The photoassimilation of 2H 2 with 1CO 2 apparently involves little over all energy change but nevertheless requires 4 quanta. 相似文献
14.
Incorporation of 18O into CO 2 was measured under various buffer conditions when the bioluminescent oxidation of Cypridina luciferin, catalyzed by luciferase, was carried out either in H 216O medium with 18O 2 gas, or in H 218O medium with 16O 2 gas. The results indicate that (1) the exchange of oxygen between CO 2 and solvent H 2O is significantly influenced by the kind of buffer as well as by pH, (2) the exchange of oxygen between solvent H 2O and CO 2 produced from luciferin in a neutral buffer can be reasonably well estimated from the exchange that takes place when the same amount of CO 2 gas is introduced into the same buffer by the presently employed method, and (3) in the Cypridina bioluminescent reaction, one of two oxygens of O 2 is quantitatively incorporated into the product CO 2 prior to the exchange of oxygen between CO 2 and solvent H 2O. 相似文献
15.
The O-methyl substituents of aromatic compounds constitute a C 1 growth substrate for a number of taxonomically diverse anaerobic acetogens. In this study, strain TH-001, an O-demethylating obligate anaerobe, was chosen to represent this physiological group, and the carbon flow when cells were grown on O-methyl substituents as a C 1 substrate was determined by 14C radiotracer techniques. O-[ methyl- 14C]vanillate (4-hydroxy-3-methoxy-benzoate) was used as the labeled C 1 substrate. The data showed that for every O-methyl carbon converted to [ 14C]acetate, two were oxidized to 14CO 2. Quantitation of the carbon recovered in the two products, acetate and CO 2, indicated that acetate was formed in part by the fixation of unlabeled CO 2. The specific activity of 14C in acetate was 70% of that in the O-methyl substrate, suggesting that only one carbon of acetate was derived from the O-methyl group. Thus, it is postulated that the carboxyl carbon of the product acetate is derived from CO 2 and the methyl carbon is derived from the O-methyl substituent of vanillate. The metabolism of O-[ methyl- 14C]vanillate by strain TH-001 can be described as follows: 3 14CH 3OC 7H 5O 3 + CO 2 + 4H 2O → 14CH 3COOH + 2 14CO 2 + 10H + + 10e - + 3HOC 7H 5O 3. 相似文献
16.
The catalase activity of unwashed preparations containing intact spinach ( Spinacia oleracea L.) chloroplasts is inhibited both by cyanide and by azide at concentrations which also cause inhibition of photosynthetic CO 2- dependent O 2 evolution. Aminotriazole can also be used to inhibit this contaminant catalase, and in this case inhibition of catalase can be achieved at aminotriazole concentrations which have little effect on the rate of photosynthetic CO2 fixation. Aminotriazole may be used as a specific inhibitor of catalase in order to demonstrate inhibition of photosynthesis by added H2O2. It is therefore concluded that inhibition of photosynthesis by cyanide and azide does not necessarily result from inhibition of catalase in the chloroplast preparation, and that intact chloroplasts do not produce inhibitory concentrations of H2O2 under the best experimental conditions for CO2 fixation. 相似文献
17.
The effect of Ca on senescence was followed in detached cucumber ( Cucumis sativus L.) cotyledons floating on various solutions in the dark. Compared with those in water, cotyledons in 10 −4 molar CaCl 2 exhibited reduced chlorophyll loss and H 2O 2 production, reduced and delayed ethylene production, and did not undergo a burst in CO 2 production. In contrast, Mg had little effect on cotyledon senescence, whereas K stimulated chlorophyll loss but did not increase H 2O 2 accumulation of ethylene and CO 2 production. This reduction in the rate of senescence by Ca could also be achieved by increasing the endogenous levels of Ca in the cotyledons before excision, although the reduction was less than that with Ca in the external solution. The addition of H 2O 2 to the solutions on which cotyledons were floated stimulated chlorophyll breakdown, but effects on ethylene and CO 2 were not consistent. 相似文献
18.
1. Gradients of hydrogen ion concentration across Fucus eggs growing in sea water determine the developmental polarity of the embryo. 2. Gradients may determine polarity even if removed before the morphological response begins. 3. The rhizoid forms on the acid side of the egg unless this is too acid, in which case it develops on the basic side of the egg. 4. Since gradients of hydrogen ion concentration in sea water produce gradients of CO 2 tension, as a result of chemical action on the carbonate buffer system, it is not proven whether the physiological effects are due to the hydrogen ions, or to the CO 2 which they produce in the medium. 5. The developmental response of the eggs to gradients of hydrogen ion (or CO 2) concentration provides an adequate but not an exclusive explanation of the group effect in Fucus. 6. Hydrogen ions may exert their effect by activating growth substance. Hydrogen ions or CO 2 probably also affect the underlying rhizoid forming processes in other ways as well. 相似文献
19.
When 0.1 M NaI is added to the sea water surrounding Valonia iodide appears in the sap, presumably entering as NaI, KI, and HI. As the rate of entrance is not affected by changes in the external pH we conclude that the rate of entrance of HI is negligible in comparison with that of NaI, whose concentration is about 10 7 times that of HI (the entrance of KI may be neglected for reasons stated). This is in marked contrast with the behavior of sulfide which enters chiefly as H 2S. It would seem that permeability to H 2S is enormously greater than to Na 2S. Similar considerations apply to CO 2. In this respect the situation differs greatly from that found with iodide. NaI enters because its activity is greater outside than inside so that no energy need be supplied by the cell. The rate of entrance ( i.e. the amount of iodide entering the sap in a given time) is proportional to the external concentration of iodide, or to the external product [N +] o [I -l o, after a certain external concentration of iodide has been reached. At lower concentrations the rate is relatively rapid. The reasons for this are discussed. The rate of passage of NaI through protoplasm is about a million times slower than through water. As the protoplasm is mostly water we may suppose that the delay is due chiefly to the non-aqueous protoplasmic surface layers. It would seem that these must be more than one molecule thick to bring this about. There is no great difference between the rate of entrance in the dark and in the light. 相似文献
20.
1. Fusarium tricothecoides was selected for a study of the respiratory and fermentative activities of Fusaria. "Resting cell" suspensions were investigated by the Barcroft manometric technique. 2. The results of the investigation indicate clearly that the mechanism of endogenous metabolism (respiration) is distinct from the exogenous mechanism (fermentation). Anaerobically no significant CO 2 production is apparent without added substrate. In the presence of glucose the anaerobic CO 2 evolution is practically equal to the added CO 2 evolved aerobically in the presence of added glucose. Low concentrations of iodoacetate or fluoride selectively poison the exogenous mechanism but do not affect the endogenous mechanism. Alcohol is not produced in the course of endogenous metabolism, but is produced in the presence of added glucose. 3. A study of the metabolism of the organism throughout its entire growth phase from 1 to 7 days has been made. 4. The ability of suspensions of Fusarium sp. H., obtained by growth on a variety of common substrates, to attack a large number of carbon sources with the production of exogenous CO 2 was determined. It is found that organisms grown on glucose will attack only glucose, mannose, and fructose, but none of the common intermediary metabolites except pyruvic acid. Organisms grown on galactose attack galactose, as well as the other hexoses, indicating an adaptive mechanism. 5. An identical mechanism for the dissimilation of glucose, mannose, and galactose is indicated since no additive effects with these substrates were observed. Growths on non-hexose carbon sources attack glucose slightly under the experimental conditions with the evolution of CO 2, but do not attack any other substrate. This would indicate a residual glucose-dissimilating mechanism in all growths investigated. 6. Striking similarities between the general metabolism of resting suspensions of Fusarium sp. H. and resting suspensions of yeast cells are apparent. 相似文献
|