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1.
Chloroplasts with high rates of photosynthetic O2 evolution (up to 120 mol O2· (mg Chl)-1·h-1 compared with 130 mol O2· (mg Chl)-1·h-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO2 concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O2 uptake could be observed in the dark by high- and low-CO2 adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m-2·s-1 for high- and low-CO2 adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO2 adapted chloroplasts, whereas high-CO2 adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O2 evolution (Km(DIC)) was 31.1 and 156 M DIC for low- and high-CO2 adapted chloroplasts, respectively. These results demonstrate that the CO2 concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl
chlorophyll
- DIC
dissolved inorganic carbon
- Km(DIC)
coneentration of dissolved inorganic carbon required for the rate of half maximal net O2 evolution
- PFR
photon fluence rate
- SPGM
silicasol-PVP-gradient medium 相似文献
2.
Anton F. Post 《Archives of microbiology》1986,145(4):353-357
Transitions in growth irradiance level from 92 to 7 Em-2 s-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O2 evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla
chlorophyll a
- CPC
C-phycocyanin
- PS II
photosystem II
- PS I
photosystem I
- RC II
reaction center of photosystem II
- P
photosynthetic O2-evolution
- I
irradiance, Em-2 s-1
-
light utilization efficiency of cells, mmol O2·mg dry wt-1·h-1/Em-2 s-1
-
light utilization efficiency of photosynthetic apparatus, mol O2·mol Chla
-1·h-1/Em-2 s-1
- Pmax
maximal rate of O2 evolution by cells, mol O2·mg dry wt-1·h-1
- Pmax
maximal rate of O2 evolution by photosynthetic apparatus, mol O2·mol·Chla
-1·h-1
- LL
low light, E m-2 s-1
- HL
high light, E m-2 s-1
- LH
low to high light transition
- HL
high to low light transition
-
k
specific rate of adaptation, h-1
-
specific growth rate, h-1
-
Q
pool size of cell constituent, mol·mg dry wt-1
-
q
net synthesis rate of cell constituent, mol·mg dry wt-1·h-1 相似文献
3.
Desulfovibrio vulgaris (Marburg) was grown on hydrogen plus sulfate as sole energy source in a medium containing excess iron. The topography of electron transport components was investigated. The bacterium contained per mg cells (dry weight) 30U hydrogenase (1U=1 mol/min), 35 g desulfoviridin (= bisulfite reductase), 0.6 U adenosine phosphosulfate reductase, 30 mU thiosulfate reductase, 0.3 nmol cytochrome c
3 (M
r=13,000), 0.04 nmol cytochrome b, 0.85 nmol menaquinone, and 0.4 nmol ferredoxin. Hydrogenase (>95%) and cytochrome c
3 (82%) were localized on the periplasmic side and desulfoviridin (95%), adenosine phosphosulfate reductase (87%), thiosulfate reductase (74%), and ferredoxin (71%) on the cytoplasmic side of the cytoplasmic membrane; menaquinone and cytochrome b were exlusively found in the membrane fraction. The location of the oxidoreductases indicate that in D. vulgaris (Marburg) H2 oxidation and sulfate reduction take place on opposite sides of the cytoplasmic membrane rather than on the same side, as has recently been proposed. 相似文献
4.
W. -M. Weber B. Dannenmaier W. Clauss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):153-159
The dorsal skin of the leech Hirudo medicinalis was used for electrophysiological measurements performed in Ussing chambers. The leech skin is a tight epithelium (transepithelial resistance = 10.5±0.5 k· cm-2) with an initial short-circuit current of 29.0±2.9 A·cm-2. Removal of Na+ from the apical bath medium reduced short-circuit current about 55%. Ouabain (50mol·l-1) added to the basolateral solution, depressed the short-circuit current completely. The Na+ current saturated at a concentration of 90 mmol Na+·l-1 in the apical solution (K
M=11.2±1.8 mmol·l-1). Amiloride (100 mol·l-1) on the apical side inhibited ca. 40% of the Na+ current and indicated the presence of Na+ channels. The dependence of Na+ current on the amiloride concentration followed Michaclis-Menten kinetics (K
i=2.9±0.4 mol·l-1). The amiloride analogue benzamil had a higher affinity to the Na+ channel (K
i=0.7±0.2 mol·l-1). Thus, Na+ channels in leech integument are less sensitive to amiloride than channels known from vertebrate epithelia. With 20 mmol Na+·l-1 in the mucosal solution the tissue showed an optimum amiloride-inhibitable current, and the amiloride-sensitive current under this condition was 86.8±2.3% of total short-circuit current. Higher Na+ concentrations lead to a decrease in amiloride-blockade short-circuit current. Sitmulation of the tissue with cyclic adenosine monophosphate (100 mol·l-1) and isobutylmethylxanthine (1 mmol·l-1) nearly doubled short-circuit current and increased amiloride-sensitive Na+ currents by 50%. By current fluctuation analysis we estimated single Na+ channel current (2.7±0.9 pA) and Na+ channel density (3.6±0.6 channels·m-2) under control conditions. After cyclic adenosine monophosphate stimulation Na+ channel density increased to 5.4±1.1 channels·m-2, whereas single Na+ channel current showed no significant change (1.9±0.2 pA). These data present a detailed investigation of an invertebrate epithelial Na+ channel, and show the similarities and differences to vertebrate Na+ channels. Whereas the channel properties are different from the classical vertebrate Na+ channel, the regulation by cyclic adenosine monophosphate seems similar. Stimulation of Na+ uptake by cyclic adenosine monophosphate is mediated by an increasing number of Na+ channels.Abbreviations
slope of the background noise component
- ADH
antidiuretic hormone
- cAMP
cyclic adenosine monophosphate
-
f
frequency
-
f
c
coner frequency of the Lorentzian noise component
- Hepes
N-hydroxyethylpiperazine-N-ethanesulphonic acid
- BMX
isobutyl-methylxanthine
-
i
Na
single Na+ channel current
-
I
Na
max, maximal inhibitable Na+ current
-
I
SC
short circuit current
-
K
i
half maximal blocker concentration
-
K
M
Michaelis constandard error of the mean
-
S
(f)
power density of the Lorentzian noise component
-
S
0
plateau value of the Lorentzian noise component
- TMA
tetramethylammonium
- Trizma
TRIS-hydroxymethyl-amino-methane
-
V
max
maximal reaction velocity
-
V
T
transepithelial potential
-
K
half maximal blocker concentration 相似文献
5.
Dry weight and Relative Growth Rate of Lemna gibba were significantly increased by CO2 enrichment up to 6000 l CO2 l–1. This high CO2 optimum for growth is probably due to the presence of nonfunctional stomata. The response to high CO2 was less or absent following four days growth in 2% O2. The Leaf Area Ratio decreased in response to CO2 enrichment as a result of an increase in dry weight per frond. Photosynthetic rate was increased by CO2 enrichment up to 1500 l CO2 l–1 during measurement, showing only small increases with further CO2 enrichment up to 5000 l CO2 l–1 at a photon flux density of 210 mol m–2 s–1 and small decreases at 2000 mol m–1 s–1. The actual rate of photosynthesis of those plants cultivated at high CO2 levels, however, was less than the air grown plants. The response of photosynthesis to O2 indicated that the enhancement of growth and photosynthesis by CO2 enrichment was a result of decreased photorespiration. Plants cultivated in low O2 produced abnormal morphological features and after a short time showed a reduction in growth. 相似文献
6.
The activities and kinetics of the enzymes G6PDH (glucose-6-phosphate dehydrogenase) and 6PGDH (6-phosphogluconate dehydrogenase) from the mesophilic cyanobacterium Synechococcus 6307 and the thermophilic cyanobacterium Synechococcus 6716 are studied in relation to temperature. In Synechococcus 6307 the apparent K
m's are for G6PDH: 80M (substrate) and 20M (NADP+); for 6PGDH: 90M (substrate) and 25M (NADP+). In Synechococcus 6716 the apparent K
m's are for G6PDH: 550M (substrate) and 30M (NADP+); for 6PGDH: 40M (substrate) and 10M (NADP+). None of the K
m's is influenced by the growth temperature and only the K
m's of G6PDH for G6P are influenced by the assay temperature in both organisms. The idea that, in general, thermophilic enzymes possess a lower affinity for their substrates and co-enzymes than mesophilic enzymes is challenged.Although ATP, ribulose-1,5-bisphosphate, NADPH and pH can all influence the activities of G6PDH and 6PGDH to a certain extent (without any difference between the mesophilic and the thermophilic strain), they cannot be responsible for the total deactivation of the enzyme activities observed in the light, thus blocking the pentose phosphate pathway.Abbreviations G6PDH
glucose-6-phosphate, dehydrogenase
- 6PGDH
6-phosphogluconate dehydrogenase
- G6P
glucose-6-phosphate
- 6PG
6-phosphogluconate
- RUDP
ribulose-1,5-bisphosphate
- Tricine
N-Tris (hydroxymethyl)-methylglycine 相似文献
7.
James B. Russell 《Archives of microbiology》1991,155(6):559-565
Glucose-limited, continuous cultures (dilution rate 0.1 h-1) of Streptococcus bovis JB1 fermented glucose at a rate of 3.9 mol mg protein-1 h-1 and produced acctate, formate and ethanol. Based on a maximum ATP yield of 32 cells/mol ATP (Stouthamer 1973) and 3 ATP/glucose, the theoretical glucose consumption for growth would have been 2.1 mol mg protein-1 h-1. Because the maintenance energy requirement was 1.7 mol/mg protein/h (Russell and Baldwin 1979), virtually all of the glucose consumption could be explained by growth and maintenance and the YATP was 30. Glucose-limited, continuous cultures produced heat at a rate of 0.29 mW/mg protein, and this value was similar to the enthalpy change of the fermentation (0.32 mW/mg protein). Batch cultures (specific growth rate 2.0 h-1) fermented glucose at a rate of 81 mol mg protein-1 h-1, and produced only lactate. The heat production was in close agreement with the theoretical enthalpy change (1.72 versus 1.70 mW/mg protein), but only 80% of the glucose consumption could be accounted by growth and maintenance. The YATP of the batch cultures was 25. Nitrogen-limited, glucose-excess, non-growing cultures fermented glucose at a rate of 6.9 mol mg protein-1 h-1, and virtually all of the enthalpy for this homolactic fermentation could be accounted as heat (0.17 mW/mg protein). The nitrogenlimited cultures had a membrane potential of 150 mV, and nearly all of the heat production could be explained by a futile cycle of protons through the cell membrane (watts = amperes x voltage where H+/ATP was 3). The membrane voltage of the nitrogen-limited cells was higher than the glucose-limited continuous cultures (150 versus 80 mV), and this difference in voltage explained why nitrogen-limited cultures consumed glucose faster than the maintenance rate. Batch cultures had a membrane potential of 100 mV, and this voltage could not account for increased glucose consumption (more than growth plus maintenance). It appears that another mechanism causes the increased heat production and lower growth efficiency of batch cultures. 相似文献
8.
We have addressed the question, whether the reduction of caffeate in Acetobacterium woodii strain NZva16 is coupled to ATP synthesis by electron transport phosphorylation. The following results were obtained: 1. Cultures of A. woodii with H2 and CO2, grew to greater cell densities, when caffeate was also present. Caffeate was reduced to give hydrocaffeate and less acetate was formed. The cell yield based on the amount of caffeate reduced was approximately 1 g dry cells/mol. 2. Non-growing bacterial suspensions catalyzed the reduction of caffeate by H2. The specific activity (0.2–1.0 mol · min–1 · mg–1 bacterial protein) was as high as expected for a catabolic reaction. 3. The ATP content of bacteria incubated, with H2 increased from < 1 to about 7 mol per g cellular protein on the addition of caffeate. The ATP yield was calculated as 0.06 mol ATP · mol–1 caffeate from the initial velocity of ATP formation and the activity of caffeate reduction. Valinomycin together with nigericin inhibited ATP formation and caused a 2–3-fold increase of the activity of caffeate reduction. Protonophores were without, effect. 4. Caffeate in the presence of H2 caused the uptake of tetraphenylphosphonium cation by the bacteria. The uptake was abolished by valinomycin plus nigericin, and was considerably enhanced by monensin. Protonophores were without effect, even in the presence of monensin. It is concluded that caffeate reduction by H2 is coupled to ATP formation by electron transport phosphorylation. However, the failure of protonophores to prevent phosphorylation and TPP uptake cannot be explained.Abbreviations Caffeate
3,4-Dihydroxycinnamate
- Hydrocaffeate
3,4-dihydroxyphenylpropionate
- TPP+
tetraphenylphosphonium cation
- FCCP
carbonylcyanide-4-trifluoromethoxyphenylhydrazone
- TTGB
4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazol
- TCS
3,5,3,4-tetrachlorosalicylanilide 相似文献
9.
Ferric ethylenediamine di-(o-hydroxyphenylacetate) (FeEDDHA) and ferric hydroxyethylethylenediaminetriacetic acid (FeHEDTA) were evaluated as Fe sources for hydroponic growth of alfalfa (Medicago sativa L., cv. Mesilla), either dependent on N2 fixation or supplied with NO3. The hydroponic medium was maintained at pH 7.5 by addition of CaCO3. Nitrogen-fixing cultures were inoculated with Rhizobium meliloti 102 F51 and grown in medium without added nitrogen. After five to seven weeks of growth under greenhouse conditions, plants were harvested. Nitrogen fixation was measured by the acetylene reduction method.When FeEDDHA was supplied, growth of alfalfa, whether dependent on N2 fixation or supplied with NO3, was severely limited at concentrations typically used in hydroponic medium (10 or 20 M). Maximum yield of NO3-supplied alfalfa was obtained at 100 M while maximum yield of N2-fixing alfalfa was obtained in the range of 33 to 200 M FeEDDHA. Nodule fresh weights and N2 fixation rates increased with FeEDDHA concentration up to 33 M and remained essentially constant up to 200 M. With FeHEDTA, maximum yields of both NO3-grown and N2-fixing alfalfa were obtained at 10 M. Growth of NO3-supplied plants was inhibited at 200 M FeHEDTA while growth of N2-fixing plants was inhibited at 100 M FeHEDTA. The numbers of nodules per plant increased between 3.3 and 10 M FeHEDTA; however, inhibition of nodule formation occurred at a concentration of 33 M or higher. Nodule weights per plant and N2 fixation rates were depressed at 3.3 M as well as at 100 M FeHEDTA. The results suggest that alfalfa dependent on N2 fixation is more sensitive to limited Fe availability than alfalfa supplied with NO3. 相似文献
10.
Simultaneous influx of ammonium and potassium into maize roots: kinetics and interactions 总被引:4,自引:0,他引:4
The interaction between ammonium and potassium during influx was examined in roots of dark-grown decapitated corn seedlings (Zea mays L., cv. Pioneer 3369A). Influx was measured during a 10-min exposure to either (15NH4)2SO4 ranging from 10 to 200 M NH
4
+
with and without 200 M K(86Rb)Cl or to K(86Rb)Cl ranging from 10 to 200 M K+ with and without 200 M NH
4
+
as (15NH4)2SO4. The simple Michaelis-Menten model described the data well only for potassium influx in the presence of ambient ammonium. For the other three instances, the data were improved by assuming that a second influx mechanism became operative as the low-concentration phase approached saturation. Two distinct mechanisms are thus indicated for both ammonium and potassium influx within the range of 10 to 200 M.The influx mechanism operating at low concentrations showed greater affinity for potassium than for ammonium, even though the capacity for ammonium transport was twice as large as that for potassium. It is suggested that this phase involved a common transport system for the two ions and that localized low acidity next to the internal surface, following H+ extrusion, favored ammonium deprotonation and dissociation from the transport system-ammonium complex. Parallel decreases in V
max and increases in Km of the low-concentration saturable phase occurred for ammonium influx when ambient potassium was present and for potassium influx when ambient ammonium was present. The data support a mixed-type inhibition in each case. Simultaneous measurement of potassium and ammonium influx showed that they were highly negatively correlated at the lower concentrations, indicating that the extent to which influx of the inhibited ion was restricted was associated with influx of the inhibitor ion. Presence of ambient ammonium eliminated the second phase of potassium influx. In contrast, the presence of ambient potassium decreased the concentration at which the second phase of ammonium influx was initiated but did not restrict the rate.Paper no. 11131 of the Journal Series of the North Carolina Agricultural Research ServiceThe use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned 相似文献
11.
Methanobacterium thermoautotrophicum was grown on a mineral salts medium in a fermenter gassed with H2 and CO2, 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 H2 and CO2 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 H2 and CO2 concentration were hyperbolic. From reciprocal plots apparent K
s values for H2 and CO2 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 H2 or CO2. The yield increased to near 3 g mol-1 when H2 or CO2 were limiting. These findings indicate that methane formation and growth are less tightly coupled at high concentrations of H2 or CO2 in the medium than at low concentrations. The physiological significance of these findings is discussed.
K
s: H2 and CO2 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
12.
Energy requirements for growth and maintenance of Scenedesmus protuberans Fritsch in light-limited continuous cultures 总被引:1,自引:0,他引:1
Scenedesmus protuberans Fritsch was grown in light-limited continuous cultures with a light-dark cycle, at temperatures of 20° and 28° C. At 20° irradiances of 12 and 38 W m–2 were used, at 28° 38 W m–2.The relationships between growth rate and light uptake rate were of diphasic linear character. With the lower growth rates the relationships were defined with the parameters
e
, i.e. the specific maintenance rate constant, and c, the true efficiency of light energy conversion into biomass. The
e
-value was dependent on temperature, the c on irradiance.In cultures, incubated in prolonged darkness, decrease rates of biomass were comparable to the derived
e
-values.Both diphasic linear relationships between growth rate and light uptake rate and the same order of magnitude of
e
-values could be derived from literature data on other green algae. 相似文献
13.
Summary Pollen tubes ofLilium longiflorum growingin vitro were treated for 1 h with inorganic lead (Pb) and with triethyl lead (TriEL) and studied by light and electron microscopy. Pb was considerably more toxic in relation to inhibition of pollen tube growth (EC50=6 M Pb) than was TriEL (EC50=60 M TriEL). On the other hand, at almost the entire concentration range tested (25-500 M) TriEL caused aberrant tubes and tube swellings. Pb did not cause tube swellings, even at highly growth-impairing concentrations. Pb (60 M) predominantly affected the ultrastructure of the growing cell walls without impairing the distribution of the cell organelles in the tube tips. In contrast, 50 and 100 M TriEL did not visibly influence cell wall ultrastructure but it severely damaged dictyosomes; 100 M TriEL also disturbed the original order of cell organelles in the tube tips. Cortical microtubules were selectively and completely destructed by TriEL at concentrations (50 M) where no effect on polar organization of the tube tips occurred but they remained unimpaired by 60 M Pb, indicating selective and effective interaction of TriEL with these cell organelles.Abbreviations EC50
effective lead concentration causing 50% inhibition of pollen tube growth
- MTs
microtubules
- Pb
inorganic lead
- TriAL
trialkyl lead
- TriEL
triethyl lead 相似文献
14.
The presence of active mitochondria and oxidative metabolism is shown to be essential to maintain low inhibition levels by ethanol of the growth rate (), fermentation rate (v) or respiration rate () of Saccharomyces cerevisiae wild type strain S288C. Cells which have respiratory metabolism show K
i (ethanol inhibition constant) values for , v and , higher (K
i>1 M) than those of petite mutants or grande strains grown in anaerobiosis (K
i=0.7 M). In addition, the relationship between or v and ethanol concentration is linear in cells with respiratory metabolism and exponential in cells lacking respiration. When functional mitochondria are transferred to petite mutants, the resulting strain shows K
i values similar to those of the grande strain and the inhibition of and v by increasing ethanol concentrations becomes linear. 相似文献
15.
The effects of the average light irradiance (I) on growth and nitrate uptake kinetics of the cyanobacterium Oscillatoria agardhii, in nitrate-limited chemostat cultures, were studied. Light was nonsaturating for I <9.4 Wm–2, for all growth rates () studied. However, was throughout limited by the availability of nitrate. Under light-saturating conditions the kinetics of nitrate-limited growth could be adequately described by both the Monod and Droop equations. Under light-non-saturating conditions the internal nitrogen content (Q) was a function of both and I, for which new formulas were derived. The high uptake capacity (V
max) of nitrate-limited cells was independent of , but was significantly increased for cells growing at I <9.4 Wm–2. The half-saturation constant for nitrate uptake (K
s
u
) increased with increasing , but was independent of the prevailing light conditions. The effects of light during nitrate-limited growth were associated with the regulation in the nitrogen-containing pigments.The results reported herein have important consequences for the use of Q, K
s
u
and V
max values as indicators of nutrient-deficiency of natural populations. 相似文献
16.
Jurjen Frankena Henk W. van Verseveld Adriaan H. Stouthamer 《Applied microbiology and biotechnology》1985,22(3):169-176
Summary
Bacillus licheniformis S 1684 is able to produce an alkaline serine protease exocellularly. In glucose-limited chemostat cultures the specific rate of protease production was maximal at a -value of 0.22. Above this growth rate protease production was repressed. Dependent on 10–20% of the glucose input was used for exocellular product formation. The degree of reduction of exocellular products
was 4.1.Maximum molar growth yields were high and indicate a high efficiency of growth. The values of Y
glu
max
and YO
2
max
were 83.8 and 53.3, respectively. When Y
glu
max
was corrected for the amount of glucose used for product formation a value of 100.3 was obtained. These high maximum molar growth yields are most probably caused by a high Y
ATP
max
. Anaerobic batch experiments showed a Y
ATP of 14.6.Sometimes the used strain was instable in cell morphology and protease production. Non-protease producing cells most probably develop from producing cells by mutation in the rel-gene. Producing cells most probably are relaxed (rel
-) and non-producing cells stringent (rel
+).Glossary
specific growth rate (h-1)
-
Y
sub
growth yield permol substrate (g biomass/mol)
-
Y
max
maximum molar growth yield, corrected for maintenance requirements (g biomass/mol)
-
Y
max(corr)
Y
max corrected for product formation (g biomass/mol)
-
m
sub
maintenance requirements (mol/g biomass·h)
-
m
sub(corr)
maintenance requirements corrected for product formation (mol/g biomass·h)
-
Y
c
fraction of organic substrate converted in biomass
-
z
fraction of organic substrate converted in exocellular products
-
d
fraction of organic substrate converted in CO2 (g mol/g atom C)
-
Crec%
carbon recovery %
-
average degree of reduction of exocellular products
-
P/O
amount of ATP produced during electron-transport of 2 electrons to oxygen 相似文献
17.
D. F. Stiffler S. Eskandari 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(5):355-361
Larval and adult Ambystoma tigrinum were subjected to acidosis by infusing lactic acid (2 M·g-1) into the peritoneal cavity. Blood was sampled at intervals to establish the time-course of the ensuing acidosis. Both larvae and adults became significantly acidotic after 1 h. The larval acidosis was more pronounced (-4 pH units versus-2 pH units) than adults due to greater extracellular buffering capacity (higher [HCO3
-]) in adults. Both forms recovered in about 8 h. Larvae showed a typical increase in circulating norepinephrine during the initial stages of the acidosis; adults did not, having significantly lower norepinephrine titer than larvae during the acidosis. Both larvae and adults showed transient increases in PO2 during the acidosis. The 1 and 2 antagonists, timolol and butoxamine respectively, (0.2 g·g-1) were administered to separate groups of larvae. Butoxamine (2) delayed the recovery from the acidosis by prolonging the increase in arterial PCO2 and reversing the recovery of [HCO3
-]. Timolol (1) did not delay recovery. We conclude that 2 receptors are involved in the catecholamine responses to acidosis in larvae. Catecholamines appear not to play the same role in adult acid-base disturbances as they seem to in larvae.Abbreviations RBC
red blood cell 相似文献
18.
Jakob K. Kristjansson Peter Schönheit Rudolf K. Thauer 《Archives of microbiology》1982,131(3):278-282
Desulfovibrio vulgaris (Marburg) and Methanobrevibacter arboriphilus (AZ) are anaerobic sewage sludge bacteria which grow on H2 plus sulfate and H2 plus CO2 as sole energy sources, respectively. Their apparent Ks values for H2 were determined and found to be approximately 1 M for the sulfate reducing bacterium and 6 M for the methanogenic bacterium. In mixed cell suspensions of the two bacteria (adjusted to equal V
max) the rate of H2 consumption by D. vulgaris was five times that of M. arboriphilus, when the hydrogen supply was rate limiting. The apparent inhibition of methanogenesis was of the same order as expected from the different Ks values for H2. Difference in substrate affinities can thus account for the inhibition of methanogenesis from H2 and CO2 in sulfate rich environments, where the H2 concentration is well below 5 M. 相似文献
19.
Copper but not iron limitation increases astaxanthin production by Phaffia rhodozyma in a chemically defined medium 总被引:2,自引:0,他引:2
The influence of copper (0–32 M) and iron (0–108 M) on growth and astaxanthin production by Phaffia rhodozyma was studied. Copper below 3.2 M increased the astaxanthin content of the cells (from 220 to 287 g g–1) but at the expense of a slightly decreased growth (from 11.3 to 10.2 mg ml–1). In contrast, iron below 1 M decreased both the growth and astaxanthin content of the cells. Using copper limitation instead of toxic respiratory inhibitors to improve astaxanthin production has obvious advantages from the product quality, environmental and process operation points of view. 相似文献
20.
A 64-kilodalton (kDa) protein, situated in the lumen between the inner and outer envelopes of pea (Pisum sativum L.) chloroplasts (Soll and Bennett 1988, Eur. J. Biochem., 175, 301–307) is shown to undergo reversible phosphorylation in isolated mixed envelope vesicles. It is the most conspicuously labelled protein after incubation of envelopes with 33 nmol·1-1 [-32P]ATP whereas incubation with 50 mol·1-1 [-32P]ATP labels most prominently two outer envelope proteins (86 and 23 kDa). Half-maximum velocity for phosphorylation of the 64-kDa protein occurs with 200 nmol·1-1 ATP, and around 40 mol·1-1 ATP for phosphorylation of the 86- and 23-kDa proteins, indicating the operation of two distinct kinases. GGuanosine-, uridine-, cytidine 5-triphosphate and AMP are poor inhibitors of the labelling of the 64-kDa protein with [-32P]ATP. On the other hand, ADP has a potent influence on the extent of labelling (half-maximal inhibition at 1–5 mol·1-1). The ADP-dependent appearance of 32P in ATP indicates that ADP acts by reversal of kinase activity and not as a competitive inhibitor. However, the most rapid loss of 32P from pre-labelled 64-kDa protein occurs when envelope vesicles are incubated with ATP t1/2=15 s at 20 molsd1-1 ATP). This induced turnover of phosphate appears to be responsible for the rapid phosphoryl turnover seen in situ.Abbreviations LHCP
ligh-harvesting chlorophyll-a/b-binding protein
- S0.5
concentration giving half-maximal phosphorylation
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- Tricine
N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine 相似文献