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1.
Fermentative Metabolism of Chlamydomonas reinhardii: III. Photoassimilation of Acetate 总被引:2,自引:2,他引:0
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The anaerobic photodissimilation of acetate by Chlamydomonas reinhardii F-60 adapted to a hydrogen metabolism was studied utilizing manometric and isotopic techniques. The rate of photoanaerobic (N2) acetate uptake was approximately 20 μmoles per milligram chlorophyll per hour or one-half that of the photoaerobic (air) rate. Under N2, cells produced 1.7 moles H2 and 0.8 mole CO2 per mole of acetate consumed. Gas production and acetate uptake were inhibited by monofluoroacetic acid (MFA), 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) and by H2. Acetate uptake was inhibited about 50% by 5% H2 (95% N2). H2 in the presence of MFA or DCMU stimulated acetate uptake and the result was interpreted to indicate a transition from oxidative to reductive metabolism. Carbon-14 from both [1-14C]- and [2-14C]acetate was incorporated under N2 or H2 into CO2, lipids, and carbohydrates. The methyl carbon of acetate accumulated principally (75-80%) in the lipid and carbohydrate fractions, whereas the carboxyl carbon contributed isotope primarily to CO2 (56%) in N2. The presence of H2 caused a decrease in carbon lost from the cell as CO2 and a greater proportion of the acetate was incorporated into lipid. The results support the occurrence of anaerobic and light-dependent citric acid and glyoxylate cycles which affect the conversion of acetate to CO2 and H2 prior to its conversion to cellular material. 相似文献
2.
A Gram-positive bacterium which was isolated from a Finnish soil and identified as a Nocardia sp., was able to decompose lignin and to assimilate lignin degradation products as a carbon source. It could release 14CO2 from 14C-labelled methoxyl groups, side chains or ring carbons of coniferyl alcohol dehydropolymers (DHP) and from specifically 14C-labelled lignin of plant material. Furthermore, it could release 14CO2 from phenolcarboxylic and cinnamic acids and alcohols labelled in the OCH3, COOH groups, side chain or aromatic ring carbons.Non-Common Abbreviations Used DHP
dehydropolymers of coniferyl alcohol 相似文献
3.
Dissimilation of Carbon Monoxide to Acetic Acid by Glucose-Limited Cultures of Clostridium thermoaceticum 总被引:4,自引:1,他引:3
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Clostridium thermoaceticum was cultivated in glucose-limited media, and the dissimilation of CO to acetic acid was evaluated. We found that cultures catalyzed the rapid dissimilation of CO to acetic acid and CO2, with the stoichiometry obtained for conversion approximating that predicted from the following reaction: 4CO + 2H2O → CH3CO2H + 2CO2. Growing cultures formed approximately 50 mmol (3 g) of CO-derived acetic acid per liter of culture, with the rate of maximal consumption approximating 9.1 mmol of CO consumed/h per liter of culture. In contrast, resting cells were found not to dissimilate CO to acetic acid. 14CO was incorporated, with equal distribution between the carboxyl and methyl carbons of acetic acid when the initial cultivation gas phase was 100% CO, whereas 14CO2 preferentially entered the carboxyl carbon when the initial gas phase was 100% CO2. Significantly, in the presence of saturating levels of CO, 14CO2 preferentially entered the methyl carbon, whereas saturating levels of CO2 yielded 14CO-derived labeling predominantly in the carboxyl carbon. These findings are discussed in relation to the path of carbon flow to acetic acid. 相似文献
4.
d-Glycerate Transport by the Pea Chloroplast Glycolate Carrier : Studies on [1-C]d-Glycerate Uptake and d-Glycerate Dependent O(2) Evolution 总被引:11,自引:6,他引:5
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Rapid direct conversion of exogenously supplied [14C]aspartate to [14C] asparagine and to tricarboxylic cycle acids was observed in alfalfa (Medicago sativa L.) nodules. Aspartate aminotransferase activity readily converted carbon from exogenously applied [14C]aspartate into the tricarboxylic acid cycle with subsequent conversion to the organic acids malate, succinate, and fumarate. Aminooxyacetate, an inhibitor of aminotransferase activity, reduced the flow of carbon from [14C]aspartate into tricarboxylic cycle acids and decreased 14CO2 evolution by 99%. Concurrently, maximum conversion of aspartate to asparagine was observed in aminooxyacetate treated nodules (30 nanomoles asparagine per gram fresh weight per hour. Metabolism of [14C]aspartate and distribution of nodulefixed 14CO2 suggest that two pools of aspartate occur in alfalfa nodules: (a) one involved in asparagine biosynthesis, and (b) another supplying a malate/aspartate shuttle. Conversion of [14C]aspartate to [14C]asparagine was not inhibited by methionine sulfoximine, a glutamine synthetase inhibitor, or azaserine, a glutmate synthetase, inhibitor. The data did not indicate that asparagine biosynthesis in alfalfa nodules has an absolute requirement for glutamine. Radioactivity in the xylem sap, derived from nodule 14CO2 fixation, was markedly decreased by treating nodulated roots with aminooxyacetate, methionine sulfoximine, and azaserine. Inhibitors decreased the [14C]aspartate and [14]asparagine content of xylem sap by greater than 80% and reduced the total amino nitrogen content of xylem sap (including nonradiolabeled amino acids) by 50 to 80%. Asparagine biosynthesis in alfalfa nodules and transport in xylem sap are dependent upon continued aminotransferase activity and an uninterrupted assimilation of ammonia via the glutamine synthetase/glutamate synthase pathway. Continued assimilation of ammonia apparently appears crucial to continued root nodule CO2 fixation in alfalfa. 相似文献
5.
The binding of ethyl carbamate labelled with carbon-14 in the alkyl or carbonyl group, and of methyl, n-butyl and n-propyl carbamates labelled in the alkyl group, to the DNA of mouse liver, lung and kidney has been studied in male Crackenbush mice. Only ethyl carbamate bound to liver and kidney DNA to any significant extent.The binding of ethyl carbamate labelled with carbon-14 in the C1, C2 or the carbonyl position was examined and compared. The levels of binding of [1-14C]- and [2-14C]ethyl carbamate to liver DNA were not significantly different (328 ± 34 and 267 ± 24 dpm/mg DNA, respectively), but there was very little binding of the [carbonyl-14C]ethyl carbamate (26 ± 3 dpm/mg DNA). Furthermore, only 18% of the radioactivity was removed from the DNA labelled with the alkyl-labelled carbamates, whereas 65% of the radioactivity was removed from the DNA labelled with carbonyl-labelled ethyl carbamate on continuous ether extraction. It was concluded that the bound molecule does not contain the carbonyl carbon and is probably an ethyl group. 相似文献
6.
Methanogenesis and the anaerobic metabolism of acetate were examined in the sediment and water column of Knaack Lake, a small biogenic meromictic lake located in central Wisconsin. The lake was sharply stratified during the summer and was anaerobic below a depth of 3 m. Large concentrations (4,000 μmol/liter) of dissolved methane were detected in the bottom waters. A methane concentration maximum occurred at 4 m above the sediment. The production of 14CH4 from 14C-labeled HCOOH, HCO3−, and CH3OH and [2-14C]acetate demonstrated microbial methanogenesis in the water column of the lake. The maximum rate of methanogenesis calculated from reduction of H14CO3− by endogenous electron donors in the surface sediment (depth, 22 m) was 7.6 nmol/h per 10 ml and in the water column (depth, 21 m) was 0.6 nmol/h per 10 ml. The methyl group of acetate was simultaneously metabolized to CH4 and CO2 in the anaerobic portions of the lake. Acetate oxidation was greatest in surface waters and decreased with water depth. Acetate was metabolized primarily to methane in the sediments and water immediately above the sediment. Sulfide inhibition studies and temperature activity profiles demonstrated that acetate metabolism was performed by several microbial populations. Sulfide additions (less than 5 μg/ml) to water from 21.5 m stimulated methanogenesis from acetate, but inhibited CO2 production. Sulfate addition (1 mM) had no significant effect on acetate metabolism in water from 21.5 m, whereas nitrate additions (10 to 14,000 μg/liter) completely inhibited methanogenesis and stimulated CO2 formation. 相似文献
7.
R C Hart K E Stempel P D Boyer M J Cormier 《Biochemical and biophysical research communications》1978,81(3):980-986
The use of a fully active, synthetic analogue of coelenterate-type luciferin labeled in the carbonyl position with 14C and 18O was used to probe the mechanism of the luciferase catalyzed oxidative decarboxylation of this compound. In the presence of 17O2, the CO2 produced in this oxidation can be shown to contain approximately one 17O atom per CO2 molecule. This result is consistent with a cyclic peroxide or dioxetanone-type mechanism. In the presence of luciferase, the oxygen in the luciferin carbonyl group is rapidly exchanged with solvent water prior to the production of CO2. Thus, the CO2 contains considerable oxygen derived from water, via exchange with the carbonyl group, and about one oxygen from O2 via a cyclic peroxide. 相似文献
8.
A bacterium, tentatively identified as an Arthrobacter sp., was isolated from flooded soil that was incubated at 35°C and repeatedly treated with carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methylcarbamate). This bacterium exhibited an exceptional capacity to completely mineralize the ring-labeled 14C in carbofuran to 14CO2 within 72 to 120 h in a mineral salts medium as a sole source of carbon and nitrogen under aerobic conditions. Mineralization was more rapid at 35°C than at 20°C. No degradation of carbofuran occurred even after prolonged incubation under anaerobic conditions. The predicted metabolites of carbofuran, 7-phenol (2,3-dihydro-2,2-dimethyl-7-benzofuranol) and 3-hydroxycarbofuran, were also metabolized rapidly. 7-Phenol, although formed during carbofuran degradation, never accumulated in large amounts, evidently because of its further metabolism through ring cleavage. The bacterium readily hydrolyzed carbaryl (1-naphthyl N-methylcarbamate), but its hydrolysis product, 1-naphthol, resisted further degradation by this bacterium. 相似文献
9.
When Avena coleoptile segments are immersed in a solution containing H14CO3−, the appearance of label in the tissue is stimulated approximately 3-fold by fusicoccin application. This effect is rapid (1-2 minutes lag time), dependent upon respiratory energy, inhibited by carbonyl cyanide m-chlorophenylhydrazone, but not appreciably altered by cycloheximide treatment. A large percentage of the cellular radioactivity is found in the form of malate. Preliminary experiments indicate that CO2, as opposed to HCO3−, is the favored species of “CO2” taken up by the segments. These results are consistent with the notion that CO2, presumably by virtue of its fixation and conversion to malic acid, participates in the early events associated with fusicoccin-enhanced acidification of the cell wall region leading to the stimulation of cell extension growth. 相似文献
10.
Servaites JC 《Plant physiology》1977,60(4):461-466
Isolated soybean (Glycine max [L.] Merr.) leaf cells were treated with three inhibitors of the glycolate pathway in order to evaluate the potential of such inhibitors for increasing photosynthetic efficiency. Preincubation of cells under acid conditions in α-hydroxypyridinemethanesulfonic acid increased 14CO2 incorporation into glycolate, but severely inhibited photosynthesis. Isonicotinic acid hydrazide (INH) increased the incorporation of 14CO2 into glycine and reduced label in serine, glycerate, and starch. Butyl 2-hydroxy-3-butynoate (BHB) completely and irreversibly inhibited glycolate oxidase and increased the accumulation of 14C into glycolate. Concomitant with glycolate accumulation was the reduction of label in serine, glycerate, and starch, and the elimination of label in glycine. The inhibitors INH and BHB did not eliminate serine synthesis, suggesting that some serine is synthesized by an alternate pathway. The per cent incorporation of 14CO2 into glycolate by BHB-treated cells or glycine by INH-treated cells was determined by the O2/CO2 ratio present during assay. Photosynthesis rate was not affected by INH or BHB in the absence of O2, but these compounds increased the O2 inhibition of photosynthesis. This finding suggests that the function of the photorespiratory pathway is to recycle glycolate carbon back into the Calvin cycle, so if glycolate metabolism is inhibited, Calvin cycle intermediates become depleted and photosynthesis is decreased. Thus, chemicals which inhibit glycolate metabolism do not reduce photorespiration and increase photosynthetic efficiency, but rather exacerbate the problem of photorespiration. 相似文献
11.
Aerobic and anaerobic chloroplastic respiration was monitored by measuring 14CO2 evolution from [14C]glucose in the darkened spinach (Spinacia oleracea) chloroplast and by estimating the conversion of fructose 1,6-bisphosphate to glycerate 3-phosphate in the darkened spinach chloroplast in air with O2 or in N2 with nitrite or oxaloacetate as electron acceptors. The pathway of 14CO2 evolution from labeled glucose in the absence and presence of the inhibitors iodoacetamide and glycolate 2-phosphate under air or N2 were those expected from the oxidative pentose phosphate cycle and glycolysis. Of the electron acceptors, O2 was the best (2.4 nanomoles CO2 per milligram chlorophyll per hour), followed by nitrite and oxaloacetate. With respect to glycerate 3-phosphate formation from fructose 1,6-bisphosphate, methylene blue increased the aerobic rate from 3.7 to 5.4 micromoles per milligram chlorophyll per hour. A rate of 4.8 micromoles per milligram chlorophyll per hour was observed under N2 with nitrite and oxaloacetate. 相似文献
12.
Barley roots contain a CO2 sensitive respiratory fraction which is inhibited in 50 per cent CO2 and is partially restored upon subsequent exposure to air. The residual O2 consumption occurring at CO2 concentrations between 50 per cent and 95 per cent amounts to about 40 per cent of the O2 uptake in air and can support K+ uptake for a limited time at a rate equal to or higher than occurs in air. Above 95 per cent CO2 both O2 and K+ uptakes decrease rapidly. 2,4-dinitrophenol (DNP), in the range of 10?6 to 10?5M, stimulates O2 uptake by the roots in air. The stimulation is absent when roots are treated with DNP in 80 per cent CO2, presumably because of the reduced demand for inorganic phosphate and phosphate acceptor at the lower respiratory level in high CO2. In either air or CO2, K+ uptake is strongly inhibited by DNP. A comparison of the respiratory and K+ uptake data indicates that O2 consumption is a necessary requirement for the uptake process in high CO2. Protoplasmic streaming in the root cells is rapidly stopped by high CO2 although K+ uptake and O2 consumption continue. The cation uptake mechanism in high CO2 appears to be limited to the stationary cytoplasm. It is also possible that a similar mechanism may be involved in cation uptake in air. 相似文献
13.
Substrates for Sulfate Reduction and Methane Production in Intertidal Sediments 总被引:16,自引:12,他引:4
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The activity of and potential substrates for methane-producing bacteria and sulfate-reducing bacteria were examined in marsh, estuary, and beach intertidal sediments. Slow rates of methane production were detected in all sediments, although rates of sulfate reduction were 100- to 1,000-fold higher. After sulfate was depleted in sediments, the rates of methane production sharply increased. The addition of methylamine stimulated methanogenesis in the presence of sulfate, and [14C]methylamine was rapidly converted to 14CH4 and 14CO2 in freshly collected marsh sediment. Acetate, hydrogen, or methionine additions did not stimulate methanogenesis. [methyl-14C]methionine and [2-14C]acetate were converted to 14CO2 and not to 14CH4 in fresh sediment. No reduction of 14CO2 to 14CH4 occurred in fresh sediment. Molybdate, an inhibitor of sulfate reduction, inhibited [2-14C]acetate metabolism by 98.5%. Fluoracetate, an inhibitor of acetate metabolism, inhibited sulfate reduction by 61%. These results suggest that acetate is a major electron donor for sulfate reduction in marine sediments. In the presence of high concentrations of sulfate, methane may be derived from novel substrates such as methylamine. 相似文献
14.
Use of Carbon Isotopes to Estimate Incorporation of Added CO(2) by Greenhouse-Grown Tomato Plants
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A method is presented which uses the 13C and 14C isotope abundance in CO2-enriched greenhouse crops to determine the percentage of plant organic carbon derived from artificially added CO2. In a greenhouse experiment with CO2 concentrations elevated to 1100 ± 100 microliters per liter during part of the daylight hours and maintained at normal atmospheric concentrations (340 microliters per liter) during the rest of the time, it was shown by 14C analysis that between 41% and 42% of the carbon in tomato plants (Lycopersicon esculentum var 4884) came from the artificially added CO2. Similar results were obtained from 13C analyses when the CO2 pressure-dependent isotope separation was taken into account. 相似文献
15.
M. Megharaj H. W. Pearson K. Venkateswarlu 《Applied microbiology and biotechnology》1993,39(4-5):644-648
A microalga, Chlorella vulgaris, and two diazotrophic cyanobacteria, Nostoc linckia and N. muscorum, all isolated from a rice soil, were compared for their response in terms of growth and metabolic activities to the application of carbofuran. The toxicity criteria included cell constituents (chlorophyll a, total protein, carbohydrate), 14CO2 uptake and nitrate reductase, besides nitrogenase activity (acetylene reduction) in the cyanobacteria. C. vulgaris and N. muscorum were more sensitive to carbofuran than was N. linckia. The significant toxicity of the insecticide, observed with higher concentrations of 20 and 50 g ml–1, to nitrogenase activity in N. linckia was reversed by the addition of ATP at 10 M. Transmission electron microscopy of the cultures, exposed to 50 g carbofuran ml–1 showed certain cellular abnormalities, indicating interference of the insecticide with membrane properties.
Correspondence to: K. Venkateswarlu 相似文献
16.
Effect of silver ion, carbon dioxide, and oxygen on ethylene action and metabolism 总被引:5,自引:17,他引:5
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Beyer EM 《Plant physiology》1979,63(1):169-173
The relationship between ethylene action and metabolism was investigated in the etiolated pea seedling (Pisum sativum L. cv. Alaska) by inhibiting ethylene action with Ag+, high CO2, and low O2 and then determining if ethylene metabolism was inhibited in a similar manner. Ag+ (100 milligrams per liter) was clearly the most potent antiethylene treatment. Ag+ pretreatment inhibited the growth retarding action of 0.2 microliters per liter ethylene by 48% and it also inhibited the incorporation of 0.2 microliters per liter 14C2H4 into pea tips by the same amount. As the ethylene concentration was increased from 0.2 to 30 microliters per liter, the effectiveness of Ag+ in reducing ethylene action and metabolism declined in a similar fashion. Although Ag+ significantly inhibited the incorporation of 14C2H4 into tissue metabolites, the oxidation of 14C2H4 to 14CO2 was unaffected in the same tissue. 相似文献
17.
Acetyl transport mechanisms in the nervous system. The oxoglutarate shunt and fatty acid synthesis in the developing rat brain 总被引:8,自引:4,他引:4
Abstract Radioactive acetyl groups and lipids are produced from dl -[5-14C]glutamate. Degradation studies indicate that approximately 90 per cent of the radioactivity is localized in the original carboxyl groups of the two carbon unit. Since these results are shown not to be due to a 14CO2 fixation, it is concluded that the oxoglutarate shunt as an acetyl group transport system is functional in brain. The highest ratio of fatty’acid activity/CO2 activity in this pathway is found in the newborn rat brain and steadily decreases with development. This pattern is observed with incubations of brain slices with labelled glutamate or citrate and is similar to the changes observed in the activity of the citrate cleavage enzyme with brain maturation. In contrast to the previous studies with liver preparations, the conversion of [2-14C]- and [5-14C]glutamate to fatty acids is relatively small. This is particularly true during the period of maximal lipid synthesis. 相似文献
18.
M. Čerňáková 《Folia microbiologica》1993,38(4):331-334
The effect of the insecticide Nerametrine EK-15 (containing an active supercypermetrine component) on nitrification, nitrogen
fixation, CO2 production and cellulase activity of soil microorganisms was investigated. Four soil types were sampled from various localities.
Supercypermetrine at 31 pmol/kg soil affected remarkably the metabolic activity of all soil samples tested by producing CO2 after a 1-d exposure. After a 14-d exposure no difference in the metabolic activity related to CO2 production was noticed in the case of garden soil where the insecticide at 31 pmol/kg soil and the unaffected control were
used. As far as other samples are concerned, the supercypermetrine concentration amounting to 31 pmol/kg soil explicitly inhibited
the metabolic activity of soil microorganisms. On the other hand, concentrations of 0.61 and 6.1 pmol/kg soil stimulated the
metabolic activity of soil in the locality of Senica. The soil samples enriched with nutrients (organic nitrogen in urea)
manifested an evident inhibition at 31 pmol/kg soil. The nitrification activity of all soil types was interrupted at 61 pmol/kg
soil. Supercypermetrine 0.12 pmol/L stopped completely nitrogen fixation withA. chroococcum and that corresponding to 0.3 pmol/L stopped aerobic cellulase decomposition. 相似文献
19.
Beyer EM 《Plant physiology》1975,56(2):273-278
The effects of various treatments on the recently reported system in pea (Pisum sativum cv. Alaska), which results in (a) the incorporation of 14C2H4 into the tissue and (b) the conversion of 14C2H4 to 14CO2, was investigated using 2-day-old etiolated seedlings which exhibit a maximum response. Heat treatment (80 C, 1 min) completely inhibited both a and b, whereas homogenization completely inhibited b but only partially inhibited a. Detaching the cotyledons from the root-shoot axis immediately before exposing the detached cotyledons together with the root-shoot axis to 14C2H4 markedly reduced both a and b. Increasing the 14C2H4 concentration from 0.14 to over 100 μl/l progressively increased the rate of a and b with tissue incorporation being greater than 14C2H4 to 14CO2 conversion only below 0.3 μl/l 14C2H4. Reduction of the O2 concentration reduced both a and b, with over 99% inhibition occurring under anaerobic conditions. The addition of CO2 (5%) severely inhibited 14C2H4 to 14CO2 conversion without significantly affecting tissue incorporation. Exposure of etiolated seedlings to fluorescent light during 14C2H4 treatment was without effect. Similarly, indoleacetic acid, gibberellic acid, benzyladenine, abscisic acid, and dibutyryl cyclic adenosine monophosphate had no significant effect on either a or b. 相似文献
20.
Brain cortex slices from fed, 48 h and 120 h fasted rats were incubated and 14CO2 was measured from (a) [U-14C]glucose (5 mm ) either alone or in the presence of l -lcucine (0.1 or 1 mm ), and (b) [U-14C]leucine or [l-14C]leucine at 0.1 or 1 mm with or without glucose (5 mm ). In other experiments, sodium dl -3-hydroxybutyrate (3-OHB) or acetoacetate (AcAc) at 1 or 5 mm were added in the above incubation mixture. The rate of conversion of [U14C]glucose to CO2 was decreased 20% by leucine at 1 mm and 30–50% by 3-OHB at 1 or 5 mm but not by leucine at 0.1 mm . The effects of 3-OHB and of leucine (1 mm ) were not additive. The effects of leucine were similar in the fed and fasted rats. The rate of conversion of [U-14C]leucine or [l-,4C]leucine to 14CO2 at 0.1 mm and 1.0 mm was increased by glucose (35%) in the fed or fasted rats. Ketone bodies in the absence of glucose had no effect on leucine oxidation. However, the stimulatory effect of glucose on the rate of conversion of leucine to CO2 was inhibited by 3-OHB at 5 mm . These results suggest that (a) leucine in increased concentrations (1 mm ) may reduce glucose oxidation by brain cortex while itself becoming an oxidative fuel for brain, and (b) leucine oxidation by brain may be influenced by the prevailing glucose and ketone concentrations. 相似文献