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1.
Summary High pressure/high temperature investigations on thermophilic methanogens require specific precautions to provide well-defined pH conditions in their culture media. Applying CO 2 as carbon source, sufficient buffering capacity of the culture medium is of crucial importance in investigations involving elevated pressures. In order to separate pressure effects on the growth and reproduction of thermophilic methanogens from pressure-induced protonation/deprotonation and increased solubility of gaseous components, direct pH measurements in common culture media in the absence and in the presence of CO 2 were performed at elevated temperature (65° C), and at pressures up to 100 MPa. Neutral phosphate buffer at high pressure shows a significant downward shift of its pH which is strongly enhanced in the presence of CO 2. In minimal media containing acetate, carbonate, formate and phosphate in 100 mM concentrations, 120 mM HEPES is found to provide optimum pH stability: near neutrality the pH change upon CO 2 saturation in the absence and in the presence of HEPES amounts to pH=2.10 and 0.41, respectively; the corresponding pressure dependences are pH/100 MPa=-0.26 and -0.07. As taken from these results, the apparent pressure dependence of the optimum growth of Methanococcus thermolithotrophicus at 65° C in minimal medium reflects the pH shift below the cutoff point of growth (pH 5.5), rather than pressure-induced growth inhibition. At constant pH, elevated pressure up to 400 MPa is found to increase the rate and yield of growth; at the same time, alterations in the phenotype of the bacterium are observed. 相似文献
2.
Summary The rate of glycolate excretion by Coccochloris peniocystis Kütz. cells incubated under conditions of low bicarbonate concentration and high light intensity was linear for only the initial 15 min of incubation and no additional glycolate accumulated in the medium after 20 min. Excretion was maximal in cells grown on 5% CO 2 in air when transferred to an incubation medium containing no added bicarbonate. The inhibitor INH (isonicotinyl hydrazide) had no measurable effect on the amount of glycolate released whereas HPMS (-hydroxy-2-pyridyl methanesulfonate) stimulated excretion 3-fold. Cells transferred to air from growth on 5% CO 2 in air increased in carbonic anhydrase activity, while a decrease occurred in the cells' ability to excrete glycolate. Cells grown on air and switched to 5% CO 2 in air showed an increase in their ability to excrete glycolate with a concomitant decrease in carbonic anhydrase activity. Diamox, a specific inhibitor of carbonic anhydrase, was found to stimulate excretion with both airgrown and 5% CO 2-grown cells which had been off 5% CO 2 for approximately 30 min. The rate of carbon fixation by 5% CO 2-grown cells put on air was found to rise over a 110 min period, corresponding to both the induction period of carbonic anhydrase and the period of decline in the ability of the cells to excrete glycolic acid. These results suggest that the absence of carbonic anhydrase in 5% CO 2-grown cells causes a stimulation of glycolate excretion when these cells are transferred to a low bicarbonate medium, because of an increased rate of glycolate formation due to the oxidation of ribulose diphosphate by molecular oxygen at low internal CO 2 concentrations.Abbreviations INH
isonicotinyl bydrazide
- HPMS
-hydroxy-2-pyridyl methanesulfonate 相似文献
3.
Cupric ion (Cu ++) inhibits the rate of photosystem II electron transport and the intensity of the variable part of chl a fluorescence in isolated chloroplast thylakoids. The inhibition is markedly dependent on the nature of the buffer used in the assay medium. In MES and HEPES buffers, complete inhibition of photosystem II occurs at 30 M of Cu ++, while in Tricine no inhibition occurred even at 200 M Cu ++. In other buffers used (TES, Phosphate, Tris), the efficacy of Cu ++ inhibition is intermediate. The calculated binding constants are found to correspond to the observed I 50 values for the six buffers used. It is concluded that the previous reports on copper inhibition, where buffers have been used indiscriminately should be reconsidered. Certain reagents such as hydroxylamine, ascorbate and diphenyl carbazide, which react with Cu ++, should be avoided.Abbreviations Chl
chlorophyll
- DCIP
2,6-dichlorophenol indophenol
- DCMU
3-(3,4 dichlorophenyl)-1,1-dimethyl urea
- DAD
diaminodurene
- DPC
diphenyl carbazide
- Fv
variable chl fluorescence
- HEPES
N-2-hydroxyethyl piperazine sulfonic acid
-
I
30
inhibitor concentration causing 30% inhibition of Fv
- MES
2-(N-morpholino) ethane sulfonic acid
- MV
Methyl viologen
- PS II
Photosystem II
- PS I
Photosystem I
- TES
N-tris(hydroxymethyl)-methyl-2-amino sulfonic acid
- TMPD
N,N,N,N-tetramethyl-p-phenylenediamine
- Tricine
N-tris(hydroxymethyl) ethylglycine
- Tris
N-tris(hydroxymethyl)amino ethane 相似文献
4.
A procedure is described for the rapid establishment of photoautotrophic protoplast-derived cultures of Nicotiana plumbaginifolia. Photoautotrophic growth was induced by lowering the glucose concentration to 2.5 g.l –1 in the protoplast culture medium and by omitting glucose from the subsequent dilution medium. Four week-old highly viable suspensions were plated on an agar-medium without glucose in unsealed Petri dishes and kept in illuminated chambers flushed with 0.05 % or 2 % CO 2. Air-grown calli had net photosynthesis rates of 1.8 and 17 moles CO 2.g –1 fresh wt.h –1 in air at 0.034 % CO 2 and in air enriched with 1 % CO 2, respectively. Calli grown in 2 % CO 2 exhibited lower rates of net photosynthesis at the two CO 2 concentrations tested (0 and 7.5 moles CO 2.g –1 fresh wt.h –1, respectively). The contribution of photosynthesis to growth was estimated to be 80 % in air-grown calli and more than 90 % in calli grown in 2 % CO 2. The suitability of this photoautotrophic culture procedure is discussed with regard to the screening of photosynthetic mutants or transformants from protoplasts.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- BAP
6-benzylaminopurine
- IAA
indoleacetic acid
- Rubisco
ribulose 1,5-bisphosphate carboxylase/oxygenase 相似文献
5.
The photoautotrophic micropropagation of potato cv. Russet Burbank was investigated. Single node microcuttings were grown for four weeks on Murashige and Skoog (MS) medium with or without sucrose (30 g l –1) in the growth room at 21/19 °C day/night temperature, with 16-h photoperiod at 150 mol m –2 s –1, with or without supplemental CO 2 at 1500 l l –1. A 20% increase in the number of nodes per stem (from 7.5 to 9.4) and a 50% increase in stem dry weight were observed in cultures grown on media with sucrose and in CO 2 enriched atmosphere comparing to the conventionally micropropagated cultures or the cultures grown photoautotrophically on media without sucrose but in air supplemented with 1500 l l –1CO 2. Stems of these cultures (from media with sucrose in CO 2 enriched air) almost doubled in length the stems of cultures from the other two treatments. No significant differences were observed between Control (MS medium supplemented with sucrose, 30 g l –1) and photoautotrophic cultures coming from MS medium with no sucrose grown under 1500 l l –1 of CO 2. Photoautotrophic cultures produced stems averaging 43.3 mm, with 7 nodes and weighing 9.2 mg (dry weight), similar to conventionally grown in vitro cultures (47.9 mm with 7.5 nodes, 9.7 mg dry weight). Growers may consider photoautotrophic culturing of potato in areas where the high sterility levels are difficult to maintain. Supplementing air in the growth room with 1500 l l –1 of CO 2 could be beneficial for potato plantlet production even on media containing sucrose since it significantly improved quality, size and biomass of produced plantlets, speeding up the multiplication. 相似文献
6.
The effects of nitrate and silicate levels, and carbon source on growth, biochemical composition and fatty acid composition of Nitzschia inconspicua were investigated using batch cultures. Within the range of silicate levels supplied (8.8–176 M), no marked variations in growth trend, biochemical composition or fatty acid composition were shown. Biomass at stationary phase, ranging from 64–66 mg ash-free dry weight (AFDW) L –1, and specific growth rate () based on chlorophyll a (0.41–0.50 d –1) of the cultures grown within 0.3–3.0 mM NaNO 3 were not significantly different. Cultures supplemented with glucose (0.1 % w/v), acetate (0.1 % w/v) or 5% CO 2 attained higher biomass (85, 85, 97 mg AFDW L –1) than the control which was grown in synthetic seawater and agitated by magnetic stirring. Cells grown at <3.0 mM NaNO 3 contained higher carbohydrate contents (14.8–21.5% AFDW) than those grown at 3.0 mM (4.0% AFDW). Lipid content increased at the expense of proteins in cells aerated with 5% CO 2. The dominant fatty acids, 16:0 and 16:1, ranged from 35.7–45.0% and 36.4–45.4% total fatty acids (TFA), respectively, while the relative proportions of 20:4 (n-6) and 20:5 (n-3) ranged from 1.7–5.4% and 3.4–5.9% TFA respectively. Cultures aerated with 5% CO 2 attained the highest biomass (97 mg AFDW L –1) and yield of 20:5 (n-3) (0.34 mg L –1). 相似文献
7.
Chlorobium limicola has been proposed to assimilate CO 2 autotrophically via a reductive tricarboxylic acid cycle rather than via the Calvin cycle. This proposal has been a matter of considerable controversy. In order to determine which pathway is operative, the bacterium was grown on a mineral salts medium with CO 2 as the main carbon source supplemented with specifically labeled 14C-pyruvate, and the incorporation of 14C into alanine (intracellular pyruvate), aspartate (oxaloacetate), glutamate (-ketoglutarate), and glucose (hexosephosphate) was measured in exponentially growing cells in long term labeling experiments. During growth in presence of pyruvate, 20% of the cell carbon were derived from pyruvate in the medium, 80% from CO 2. Since pyruvate was not oxidized to CO 2, only those compounds should become labeled which were synthesized from CO 2 via pyruvate.The three amino acids and glucose were found to be labeled. Alanine had one fifth the specific radioactivity of the extracellular pyruvate, indicating that 20% of the intracellular pyruvate pool were derived from pyruvate in the medium, 80% were synthesized from CO 2. Glucose had twice the specific radioactivity of alanine, showing that hexosephosphate synthesis from CO 2 proceeded via the pyruvate pool. The latter finding is not consistent with the operation of the Calvin cycle, in which pyruvate is not an intermediate. The specific radioactivities of aspartate (oxaloacetate) and of glutamate (-ketoglutarate) were practically identical but considerably lower than that of alanine ( intracellular pyruvate). These findings are compatible with the operation of a reductive tricarboxylic acid cycle as mechanism of autotrophic CO 2 fixation. Degradation studies of the cell components support this interpretation.
Offprint requests to: G. Fuchs 相似文献
8.
Experiments were designed to determine the significance of dark CO 2 fixation in excised maize roots, carrot slices and excised tomato roots grown in tissue culture. Bicarbonate- 14C was used to determine the pathway and amounts of CO 2 fixation, while leucine- 14C was used to estimate protein synthesis in tissues aerated with various levels of CO 2. Organic acids were labeled from bicarbonate-14C, with malate being the major labeled acid. Only glutamate and aspartate were labeled in the amino acid fraction and these 2 amino acids comprised over 90% of the 14C label in the ethanol-water insoluble residue. Studies with leucine-14C as an indicator of protein synthesis in carrot slices and tomato roots showed that those tissues aerated with air incorporated 33% more leucine-14C into protein than those aerated with CO2-free air. Growth of excised tomato roots aerated with air was 50% more than growth of tissue aerated with CO2-free air. These studies are consistent with the suggestion that dark fixation of CO2 is involved in the growth of plant tissues. 相似文献
9.
The photosynthetic characteristics of the Cymbidium plantlet in vitro cultured on Hyponex-agar medium with 2% sucrose were determined based on the measurements of CO 2 concentration inside and outside of the culture vessels. The CO 2 measurements were made with a gas chromatograph at a PPF (photosynthetic photon flux) of 35, 102 and 226 mol m -2 s -1, a chamber air temperature of 15, 25 and 35°C and a CO 2 concentration outside the vessel of approximately 350, 1100 and 3000 ppm. The net photosynthetic rates were determined on individual plantlets and were expressed on a dry weight basis. The steady-state CO 2 concentration during the photoperiod was lower inside the vessel than outside the vessel at any PPF greater than 35 mol m -2s -1 and at any chamber air temperature. The photosynthetic response curves relating the net photosynthetic rate, PPF, and CO 2 concentration in the vessel and chamber air temperature were similar to those for Cymbidium plants grown outside and other C 3 plants grown outside under shade. The results indicate that CO 2 enrichment for the plantlets in vitro at a relatively high PPF would promote photosynthesis and hence the growth of chlorophyllous shoots/plantlets in vitro and that the plantlets in vitro would make photoautotrophic growth under environmental conditions favorable for photosynthesis.Abbreviations C in
CO 2 concentration in the culture vessel
- C out
CO 2 concentration outside the vessel (in the culture room)
- PPF
photosynthetic photon flux 相似文献
10.
Summary A flask, designed for direct gassing of batch cultures of bacteria, was evaluated for its use in studying oxygen absorption rates (OAR) and suitability for physiological studies under various controlled atmospheres. Such flasks, aerated directly without shaking, yielded an OAR (up to 1.2 mmol O 2/l/min) that was comparable to or higher than those obtained in conventional flasks aerated by shaking. Direct aeration in combination with shaking resulted in OAR values that were elevated and most favorable for growth of oxygen demanding bacteria (5 mmol O 2/l/min). In comparison with controls, the direct method of aeration in combination with shaking proved most efficient and least dependent on the surface to volume ratio of the aerated solution. In experiments with the facultative anaerobe Streptococcus faecalis 10Cl, grown in controlled aerobic, anaerobic, and mixed gas (CO 2-free air, air-plus-CO 2, N 2-plus-CO 2) environments, a specific anaerobic requirement for CO 2 could be established. The wide range of gaseous environments possible renders the newly tested flask useful for comparative biochemical studies, especially when the gaseous condition of culture is a factor of critical importance. 相似文献
11.
Growth of Thermoproteus neutrophilus at 85°C was studied using an improved mineral medium with CO 2, CO 2 plus acetate, CO 2 plus propionate, or CO 2 plus succinate as carbon sources; sulfur reduction with H 2 to H 2S was the sole source of energy. None of the carbon compounds added was oxidized to CO 2. The organism grew autotrophically with a generation time of 9–14 h, up to a cell density of 0.5 g dry weight per liter (2×10 9 cells/ml). Propionate did not stimulate, succinate slightly stimulated the growth rate. Acetate, even at low concentrations (0.5 mM), stimulated the growth rate, the generation time being shortened to 3–4 h. Acetate provided 70% of the cell carbon, which shows that Thermoproteus neutrophilus is a facultative autotroph. The path of these carbon precursors into cell compounds was studied by 14C long-term labelling and investigation of enzyme activities. Propionate could not be used as a major carbon source and was incorporated only into isoleucine, probably via the citramalate pathway. Acetate was a preferred carbon source which suppressed autotrophic CO 2 fixation: acetate grown cells exhibited an incomplete citric acid cycle in which 2-oxoglutarate dehydrogenase was present, but fumarate reductase was repressed. The succinate incorporation pattern and enzyme pattern indicated that autotrophic CO 2 fixation proceeded via a yet to be defined reductive citric acid cycle. 相似文献
12.
To determine enzymatic activities in the thermotolerant strain K1 (formerly Sulfobacillus thermosulfidooxidans subsp. thermotolerans), it was grown in a mineral medium with (1) thiosulfate and Fe 2+ or pyrite (autotrophic conditions), (2) Fe 2+, thiosulfate, and yeast extract or glucose (mixotrophic conditions), and (3) yeast extract (heterotrophic conditions). Cells grown mixo-, hetero-, and autotrophically were found to contain enzymes of the tricarboxylic acid (TCA) cycle, as well as malate synthase, an enzyme of the glyoxylate cycle. Cells grown organotrophically in a medium with yeast extract exhibited the activity of the key enzymes of the Embden–Meyerhof–Parnas and Entner–Doudoroff pathways. The increased content of carbon dioxide (up to 5 vol %) in the auto- and mixotrophic media enhanced the activity of the enzymes involved in the terminal reactions of the TCA cycle and the enzymes of the pentose phosphate pathway. Carbon dioxide is fixed in the Calvin cycle. The highest activity of ribulose bisphosphate carboxylase was detected in cells grown autotrophically at the atmospheric content of CO 2 in the air used for aeration of the growth medium. The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and phospho-enolpyruvate carboxytransphosphorylase decreased with increasing content of CO 2 in the medium. 相似文献
13.
The apparent photosynthetic affinity of A. variabilis to CO 2 is greatly affected by the CO 2 concentration in the medium during growth. Halfmaximal rate of photosynthetic O 2 evolution is achieved at 10 M and 100 M inorganic carbon (C inorg) in cells grown at low-CO 2 (air) and high CO 2 (5% v/v CO 2 in air), respectively, whilst the maximum rate of photosynthesis is similar in both cases. Both high- and low-CO 2-grown Anabaena accumulate C inorg within the cell; however, the rate of accumulation and the steady-state internal C inorg concentration reached is much higher in low as compared with high-CO 2-grown cells. It is suggested that Anabaena cells actively accumulate C inorg. Measurements of the kinetics of C inorg transport indicate that the affinity of the transport mechanism for C inorg is similar (K m(C inorg(150 M) in both high- and low-CO 2-grown cells. However, V
max is 10-fold higher in the latter case. It is suggested that this higher V
max for transport is the basis of the superior capability to accumulate C inorg and the higher apparent photosynthetic affinity for external C inorg in low-CO 2-grown Anabaena. Carbonic anhydrase activity was not detectable in Anabaena, yet both photosynthetic affinity to C inorg in the medium (but not V
max) and the rate of accumulation of C inorg were inhibited by the carbonic-anhydrase inhibitor ethoxyzolamide.Abbreviations C inorg
inorganic carbon
- PEP
phosphoenol pyruvate
- RuBP
ribulose-1,5-bisphosphate
CIW-DPB Publication No. 682 相似文献
14.
Photosynthetic (oxygen evolution) and growth (biomass increase) responses to ambient pH and inorganic carbon (Ci) supply were
determined for Porphyralinearis grown in 0.5 L glass cylinders in the laboratory, or in 40 L fibreglass outdoor tanks with running seawater. While net photosynthetic
rates were uniform at pH 6.0–8.0, dropping only at pH 8.7, growth rates were significantly affected by pH levels other than
that of seawater (c. pH 8.3). In glass cylinders, weekly growth rates averaged 76% at external pH 8.0, 13% at pH 8.7 and 26%
at pH 7.0. Photosynthetic O 2 evolution on a daily basis(i.e. total O 2 evolved during day time less total O 2 consumed during night time) was similar to the growth responses at all experimental pH levels, apparently due to high dark
respiration rates measured at acidic pH. Weekly growth rates averaged 53% in algae grown in fibreglass tanks aerated with
regular air (360 mg L -1 CO 2) and 28% in algae grown in tanks aerated with CO 2-enriched air (750 mg L -1 CO 2). The pH of the seawater medium in which P. linear is was grown increased slightly during the day and only rarely reached 9.0. The pH at the boundary layer of algae submerged
in seawater increased in response to light reaching, about pH 8.9 within minutes, or remained unchanged for algae submerged
in a CO 2-free artificial sea water medium. Photosynthesis of P. linearissaturated at Ci concentrations of seawater (K 0.5560 μM at pH 8.2) and showed low photosynthetic affinity for CO 2(K 0.5 61 μM) at pH 6.0. It is therefore concluded that P. linearisuses primarily CO 2 with HCO 3
- being an alternative source of Ci for photosynthesis. Its fast growth could be related to the enzyme carbonic anhydrase whose
activity was detected intra- and extracellularly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
Methanobacterium thermoautotrophicum was grown on a mineral salts medium in a fermenter gassed with H 2 and CO 2, which were the sole carbon and energy sources. Under the conditions used the bacterium grew exponentially. The dependence of the growth rate () on the concentration of H 2 and CO 2 in the incoming gas and the dependence of the growth yield (
) on the growth rate were determined at pH 7 (the pH optimum) and 65° C (the temperature optimum).The curves relating growth rate to the H 2 and CO 2 concentration were hyperbolic. From reciprocal plots apparent K
s values for H 2 and CO 2 and max were obtained: app.
= 20%; app.
= 11%; = 0.69 h -1; t
(max)=1 h.
was 1.6 g mol -1 and almost independent of the growth rate, when the rate of methane formation was not limited by the supply of either H 2 or CO 2. The yield increased to near 3 g mol -1 when H 2 or CO 2 were limiting. These findings indicate that methane formation and growth are less tightly coupled at high concentrations of H 2 or CO 2 in the medium than at low concentrations. The physiological significance of these findings is discussed.
K
s: H 2 and CO 2 concentration supporting 0.5 max; max: specific growth rate at infinite substrate concentration; Y
s:growth yield (g dry weight/mol substrate); t
: doubling time 相似文献
16.
Excretion and absorption of glycolate by young cells of Scenedesmus obliquus (Turp.) Krüger strain D 3 grown synchronously with 2% CO 2 was compared after no pretreatment with air (CO 2-adapted) or after a 2 h adaptation to normal air (0.03% CO 2) (air-adapted). At 21% O 2, excretion occurred only from CO 2-adapted cells at high pH (pH 8.0). Under conditions where no excretion occurred, external glycolate (0.2 mM) was taken up by both air-and CO 2-adapted cells at a much faster rate at pH 5 than at pH 8. The uptake was accompanied by an apparent stoichiometric uptake of H +. CO 2-adapted algae exhibited high uptake rates that were even higher in the dark than in the light. Air-adapted algae showed high uptake rates in the light but only minimal uptake in the dark. The uptake rate was decreased to about 1/3 with 5% CO 2, except with CO 2-adapted cells in the light, in which a slight stimulation occurred. Cl - ions inhibited glycolate uptake by air-adapted cells in the light; conversely, light-stimulated Cl - uptake of these cells was inhibited by glycolate. A hypothesis is discussed according to which the internal pH regulates the uptake and release of Cl -, HCO
3
-
, and glycolate.Abbreviations DCMU
3-(3,4 dichlorophenyl)-1, 1-dimethyl urea
- FCCP
carbonyl cyanide p-trifluoro-methoxyphenylhydrazone
- HEPES
2-(4-(2-hydroxyethyl)-piperazinyl) ethanesulfonic acid
- HPMS
-hydroxypyridinemethanesulfonate
- MES
2-morpholinoethanesulfonic acid
- PCV
packed cell volume 相似文献
17.
Summary The amount of 14C-glycolate excreted by Oscillatoria sp. and Anabaena flos-aquae is less than 1% of the 14C fixed by the algae during photosynthesis. Transfer of cells grown on 5% CO 2 in air to a medium of low bicarbonate concentration or treatment of the cells with isonicotinyl hydrazide (INH) during photosynthesis, caused little increase in glycolate excretion. -Hydroxysulfonates failed to stimulate massive excretion of glycolate. Although these blue-green algae excreted little glycolate, a significant proportion of the photosynthetically fixed carbon was excreted in the form of basic, neutral and acidic compounds, and such excretion was greater in 5% CO 2-grown cells than in air-grown cells. 相似文献
18.
Five hydrogen ion buffers were compared for their usefulness in regulating pH in a model oligotrophic, moderately acidic (pH 6.0) algal growth medium. These were 3,3-dimethylglutaric acid (DMGA), tricarbaliylic acid (TCA), trans-aconitic acid (tAA), N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES) and 2-(N-morpholino) ethanesulfonic acid (MES). All buffers (2.5 mM) except HEPES limited the reduction of pH in a NH4+-based medium during growth of Chrysochromulina breviturrita Nich. to less than 0.12 units, compared with more than 2 units in an unbuffered medium. Long term growth of C. breviturrita in these media was significantly inhibited (P < 0.05) by TCA and tAA. MES was able to control pH with the minimum amount of NaOH (1.0 mM) added to the medium to adjust to pH 6.0. Four of five bacterial isolates were capable of utilizing tAA as a sole organic-C source, and no isolate could metabolize HEPES or MES. No significant differences (P > 0.05) were found in the maximum growth rates of six algal species (from five classes) in a medium with or without MES buffer, although significantly greater cell yields of Ochromonas danica Prings. were obtained in the buffered medium. MES (pK4= 6.15) was considered to be the most useful buffer in the pH range 5.0–6.5, due to its biological inertness, buffering capacity, the minimal requirement for excess base to adjust pH and its minimal metal complexing ability. 相似文献
19.
Summary The blue-green alga Anacystis nidulans (strain L 1402-1) was grown in air (0.03 vol. % CO 2) and in 3.0 vol. % CO 2 at +35° C. Levels of carbonic anhydrase were 3-fold higher in air-grown cells than in CO 2-grown algae. CO 2 content during growth has no effect on activity of RuDP carboxylase. Activities of PEP carboxylase, malic enzyme and catalase were higher in CO 2-grown Anacystis cells. In air-grown cells higher activities of malate dehydrogenase, glycolate dehydrogenase, serine-pyruvate aminotransferase and aspartate--ketoglutarate aminotransferase were found. Levels of these enzymes are relatively low compared to those in green algae and higher plants. 相似文献
20.
Comparative 14CO 2 pulse- 12CO 2 chase studies performed at CO 2 compensation ()-versus air-concentrations of CO 2 demonstrated a four-to eightfold increase in assimilation of 14CO 2 into the C 4 acids malate and aspartate by leaves of the C 3-C 4 intermediate species Panicum milioides Nees ex Trin., P. decipiens Nees ex Trin., Moricandia arvensis (L.) DC., and M. spinosa Pomel at . Specifically, the distribution of 14C in malate and aspartate following a 10-s pulse with 14CO 2 increases from 2% to 17% ( P. milioides) and 4% to 16% ( M. arvensis) when leaves are illuminated at the CO 2 compensation concentration (20 l CO 2/l, 21% O 2) versus air (340 l CO 2/l, 21% O 2). Chasing recently incorporated 14C for up to 5 min with 12CO 2 failed to show any substantial turnover of label in the C 4 acids or in carbon-4 of malate. The C 4-acid labeling patterns of leaves of the closely related C 3 species, P. laxum Sw. and M. moricandioides (Boiss.) Heywood, were found to be relatively unresponsive to changes in pCO 2 from air to . These data demonstrate that the C 3-C 4 intermediate species of Panicum and Moricandia possess an inherently greater capacity for CO 2 assimilation via phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) at the CO 2 compensation concentration than closely related C 3 species. However, even at , CO 2 fixation by PEP carboxylase is minor compared to that via ribulosebisphosphate carboxylase (EC 4.1.1.39) and the C 3 cycle, and it is, therefore, unlikely to contribute in a major way to the mechanism(s) facilitating reduced photorespiration in the C 3-C 4 intermediate species of Panicum and Moricandia.Abbreviations Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
- PEP
phosphoenolpyruvate
-
CO 2 compensation concentration
- 3PGA
3-phosphoglycerate
- SuP
sugar monophosphates
- SuP 2
sugar bisphosphates
Published as Paper No. 8249, Journal Series, Nebraska Agricultural Research Division 相似文献
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