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1.
Belão TC Leite CA Florindo LH Kalinin AL Rantin FT 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(7):905-916
The African catfish, Clarias gariepinus, possesses a pair of suprabranchial chambers located in the dorsal-posterior part of the branchial cavity having extensions
from the upper parts of the second and fourth gill arches, forming the arborescent organs. This structure is an air-breathing
organ (ABO) and allows aerial breathing (AB). We evaluated its cardiorespiratory responses to aquatic hypoxia. To determine
the mode of air-breathing (obligate or accessory), fish had the respiratory frequency (f
R) monitored and were subjected to normoxic water (PwO2 = 140 mmHg) without becoming hyperactive for 30 h. During this period, all fish survived without displaying evidences of
hyperactivity and maintained unchanged f
R, confirming that this species is a facultative air-breather. Its aquatic O2 uptake (
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} ) was maintained constant down to a critical PO2 (PcO2) of 60 mmHg, below which
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} declined linearly with further reductions of inspired O2 tension (PiO2). Just above the PcO2 the ventilatory tidal volume (V
T) increased significantly along with gill ventilation (
[(V)\dot]\textG \dot{V}_{\text{G}} ), while f
R changed little. Consequently, the water convection requirement
( [(V)\dot]\textG /[(V)\dot]\textO2 ) \left( {\dot{V}_{\text{G}} /\dot{V}{\text{O}}_{2} } \right) increased steeply. This threshold applied to a cardiac response that included reflex bradycardia. AB was initiated at PiO2 = 140 mmHg (normoxia) and air-breathing episodes increased linearly with more severe hypoxia, being significantly higher
at PiO2 tensions below the PcO2. Air-breathing episodes were accompanied by bradycardia pre air-breath, to tachycardia post air-breath. 相似文献
2.
Beth L. Young David A. S. Rosen Martin Haulena Allyson G. Hindle Andrew W. Trites 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):105-116
The ability to use heart rate (fh) to predict oxygen consumption rates (
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} ) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established
fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed
whether fh could accurately predict
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations
to describe the fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship on land. However, Steller sea lions in water displayed a different fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship after consuming a 4-kg meal compared with the fasting condition. Incorporating comparable published fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} data from Steller sea lions showed a distinct effect of feeding after a 6-kg meal. Ultimately, our study illustrated that
both feeding and physical environment are statistically relevant when deriving
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current
bioenergetic models with data gathered using these predictive fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological,
behavioral, and environmental states. 相似文献
3.
Toxic at low concentrations, phenol is one of the most common organic pollutants in air and water. In this work, phenol biodegradation
was studied in extreme conditions (80°C, pH = 3.2) in a 2.7 l bioreactor with the thermoacidophilic archaeon Sulfolobus solfataricus 98/2. The strain was first acclimatized to phenol on a mixture of glucose (2000 mg l−1) and phenol (94 mg l−1) at a constant dissolved oxygen concentration of 1.5 mg l−1. After a short lag-phase, only glucose was consumed. Phenol degradation then began while glucose was still present in the
reactor. When glucose was exhausted, phenol was used for respiration and then for biomass build-up. After several batch runs
(phenol < 365 mg l−1), specific growth rate (μX) was 0.034 ± 0.001 h−1, specific phenol degradation rate (qP) was 57.5 ± 2 mg g−1 h−1, biomass yield (YX/P) was 52.2 ± 1.1 g mol−1, and oxygen yield factor
( \textY\textX/\textO 2 ) \left( {{\text{Y}}_{{{\text{X}}/{\text{O}}_{ 2} }} } \right) was 9.2 ± 0.2 g mol−1. A carbon recovery close to 100% suggested that phenol was exclusively transformed into biomass (35%) and CO2 (65%). Molar phenol oxidation constant
( \textY\textO 2 /\textP ) \left( {{\text{Y}}_{{{\text{O}}_{ 2} /{\text{P}}}} } \right) was calculated from stoichiometry of phenol oxidation and introducing experimental biomass and CO2 conversion yields on phenol, leading to values varying between 4.78 and 5.22 mol mol−1. Respiratory quotient was about 0.84 mol mol−1, very close to theoretical value (0.87 mol mol−1). Carbon dioxide production, oxygen demand and redox potential, monitored on-line, were good indicators of growth, substrate
consumption and exhaustion, and can therefore be usefully employed for industrial phenol bioremediation in extreme environments. 相似文献
4.
Lau GY Richards JG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(7):927-939
In the present study, we test the hypothesis that AMP-activated protein kinase (AMPK) initiates metabolic rate suppression
in isolated goldfish hepatocytes. To accomplish this, we attempted to pharmacologically activate AMPK in goldfish hepatocytes
with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and the thienopyridone, A769662, to examine the effects of AMPK
activation on eukaryotic elongation factor-2 (eEF2), protein synthesis, and cellular oxygen consumption rate (
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} ). Goldfish hepatocytes treated with 1 mM AICAR under normoxic conditions (>200 μM O2) showed a modest but significant 1.1-fold increase in AMPK phosphorylation, a 7.5-fold increase in AMPK activity, a 1.4-fold
increase in eEF2 phosphorylation, and a 24% decrease in
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} . At physiologically relevant [O2] (<40 μM O2), the addition of 1 mM AICAR resulted in only a 13% decrease in cellular
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} with no change in sensitivity to [O2] as assessed by estimates of cellular P50 and P90 values. The addition of compound C, a general protein kinase inhibitor, after AICAR incubation did not reverse the effects
of AICAR on
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} in normoxia. Treatment of hepatocytes with ≤200 μM A769662 did not affect AMPK activity, AMPK phosphorylation, eEF2 phosphorylation,
or cellular
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} . These data suggest that A769662 is not an activator of AMPK in goldfish hepatocytes. Although our study provides support
for the hypothesis that AMPK plays a role in initiating metabolic rate suppression in goldfish hepatocytes, this support must
be viewed cautiously because of the known off-target effects of the pharmacological agents used. 相似文献
5.
F. Scott Gayzik J. Jason Hoth Joel D. Stitzel 《Biomechanics and modeling in mechanobiology》2011,10(4):505-520
This study explores the relationship between impact severity and resulting pulmonary contusion (PC) for four impact conditions
using a rat model of the injury. The force–deflection response from a Finite Element (FE) model of the lung was simultaneously
matched to experimental data from distinct impacts via a genetic algorithm optimization. Sprague-Dawley rats underwent right-side
thoracotomy prior to impact. Insults were applied directly to the lung via an instrumented piston. Five cohorts were tested:
a sham group and four groups experiencing lung insults of varying degrees of severity. The values for impact velocity (V)
and penetration depth (D) of the cohorts were Group 1, (V = 6.0 m · s−1, D = 5.0 mm), Group 2, (V = 1.5 m · s−1,D = 5.0 mm), Group 3, (V = 6 m · s−1, D = 2.0 mm), and Group 4, (V = 1.5 m · s−1, D = 2.0 mm). CT scans were acquired at 24 h, 48 h, and 1 week post-insult. Contusion volume was determined through segmentation.
FE-based injury metrics for PC were determined at 24 h and 1 week post-impact, based on the observed volume of contusion and
first principal strain. At 24 h post-impact, the volume of high radiopacity lung (HRL) was greatest for the severe impact
group (mean HRL = 9.21 ± 4.89) and was significantly greater than all other cohorts but Group 3. The concurrent optimization
matched simulated and observed impact energy within one standard deviation for Group 1 (energy = 3.88 ± 0.883 mJ, observed
vs. 4.47 mJ, simulated) and Group 2 (energy = 1.46 ± 0.403 mJ, observed vs. 1.50 mJ, simulated) impacts. Statistically significant
relationships between HRL and impact energy are presented. The FEA-based injury metrics at 24 h post-contusion are emax·[(e)\dot]max{\varepsilon_{\max}\cdot \dot {\varepsilon}_{\max}} exceeding 94.5 s−1, ε
max exceeding 0.284 and [(e)\dot]max{\dot{\varepsilon}_{\max}} exceeding 470 s−1. Thresholds for injury to the lung still present at 1 week post-impact were also determined. They are emax·[(e)\dot]max{\varepsilon_{\max}\cdot \dot {\varepsilon}_{\max}} exceeding 149 s−1, ε
max exceeding 0.343 and [(e)\dot]max{\dot{\varepsilon}_{\max}} exceeding 573 s−1. A mesh sensitivity study found that thresholds based on strain rate were more sensitive to changes to mesh density than
the threshold based on strain only. 相似文献
6.
Luis Arigita Ma Jesús Cañal Ricardo Sánchez Tamés Aida González 《In vitro cellular & developmental biology. Plant》2010,46(3):312-322
In traditional in vitro culture, the low CO2 concentration inside the vessels restricts photosynthesis and necessitates the addition of sucrose to the culture medium
as the main energy source, thus bringing about changes in the absorption of mineral elements from the culture medium. In this
study, we investigated macronutrient absorption and sugar consumption in Actinidia deliciosa Chevalier Liang and Ferguson cv. Hayward (kiwi), cultured on medium supplemented with varying amounts of sucrose (0, 10,
and 20 g l−1) under both heterotrophy and autotrophy, flushed with different concentrations of CO2 (non-ventilation, 300, 600, and 2,000 μl l−1). In ventilated systems with 20 g l−1 of sucrose, sucrose absorption was less than under non-ventilation. The lowest rate of sucrose absorption was recorded when
the explants were cultured on medium supplemented with 20 g l−1 of sucrose and flushed with 600 μl l−1 CO2. Absorption of NO3
−, PO4
3−, and Mg2+ were high (maximum) at the end of the culture period (40 d) in explants flushed with 600 μl l−1 CO2 that have been cultured 20 d in the presence of sucrose and then transferred to a sucrose-free medium. These autotrophic
conditions promoted maximum plant growth in terms of both fresh and dry mass as well as the length and number of shoots and
leaves. The study shows that to maintain an optimum regime of mineral nutrition for prolonged culture of kiwi in vitro, an increased amount of these three ions should be supplemented in Murashige and Skoog’s medium. 相似文献
7.
Eme J Crossley DA Hicks JW 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(3):391-401
All embryonic and fetal amniotes possess a ductus(i) arteriosus(i) that allows blood to bypass the pulmonary circulation and
the non-functional lungs. The central hemodynamic of embryonic reptiles are unique, given the additional systemic aorta that
allows pulmonary circulatory bypass, the left aorta (LAo). The LAo exits in the right ventricle or ‘pulmonary side’ of reptilian
hearts in both embryos and adults, but its functional significance in ovo is unknown. This study investigated the role of
the LAo in embryonic American alligators by surgically occluding the LAo and measuring oxygen consumption and, in addition,
measured hemodynamic responses to hypoxia in embryonic alligators. We measured systemic cardiac output and primary chorioallantoic
membrane (CAM) artery blood flow for normoxic and hypoxic-incubated (10% O2) American alligator embryos (Alligator mississippiensis). Chronic blood flow (1–124 h) in the primary CAM artery for hypoxic-incubated embryos (92 ± 26 ml min−1 kg−1) was elevated when compared with normoxic-incubated embryos (29 ± 14 ml min−1 kg−1, N = 6; P = 0.039). For hypoxic-incubated embryos, acute LAo blood flow (49.6 ± 24.4 ml min−1 kg−1) was equivalent to the combined flow of the three systemic great vessels that arise from the left ventricle, the right aorta,
common carotid and subclavian arteries (43.6 ± 21.5 ml min−1 kg−1, N = 5). Similarly, for normoxic-incubated embryos, LAo blood flow (27.3 ± 6.6 ml min−1 kg−1) did not statistically differ from the other three vessels (18.4 ± 4.9 ml min−1 kg−1, N = 5). This study contains the first direct test of LAo function and the first measurements of blood flow in an embryonic
reptile. These data support the hypotheses that embryonic alligators utilize the LAo to divert a significant amount of right
ventricular blood into the systemic circulation, and that CAM blood flow increases following chronic hypoxic conditions. However,
surgical occlusion of the LAo did not affect egg
[(V)\dot]\textO2, \dot{V}_{{\text{O}}_{2}}, supporting the hypothesis that the LAo of reptiles is not critical to maintain in ovo oxygen consumption. 相似文献
8.
Kelly M. Hare Shirley Pledger Michael B. Thompson John H. Miller Charles H. Daugherty 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(8):1173-1181
Ectotherms from low-temperature environments have higher metabolic rates at low temperatures than those from warm-temperature
environments. We predicted that nocturnal lizards, which are active at much lower environmental temperatures than diurnal
lizards, would also have higher metabolic rates at low temperatures, and by association a lower thermal sensitivity (Q
10) than diurnal and crepuscular lizards. We measured the rate of oxygen consumption (
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} ) of eight cool-temperate species of lizard (four nocturnal, three diurnal, and one crepuscular) at 13 and 26°C and analyzed
log transformations of these data using log mass as a covariate. As expected,
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} was positively correlated with temperature in all eight species, with
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} being two to four times higher at 26°C than at 13°C. As predicted, at 13°C (but not 26°C) the
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} was significantly higher in nocturnal than diurnal lizards. Species-specific differences and mass scaling factors explain
the patterns of thermal sensitivity seen among these eight lizard species. Thermal sensitivity is strongly influenced by mass,
with smaller species generally having higher thermal sensitivity of their metabolic rate, and this result deserves further
exploration among other ectotherms. We conclude that, along with the previously reported lower cost of locomotion found in
nocturnal lizards, they also partially offset the thermal handicap of activity at low body temperatures by having an elevated
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} at lower temperatures. 相似文献
9.
10.
Changes in oxygen consumption rate and Na+/K+-ATPase activity during early development were studied in the sea urchin Paracentrotus lividus Lam. The oxygen consumption rate increased from 0.12 μmol O2 mg protein−1 h−1 in unfertilized eggs to 0.38 μmol O2 mg protein−1 h−1 25 min after fertilization. Specific activity of the Na+/K+-ATPase was significantly stimulated after fertilization, ranging up to 1.07 μmol Pi h−1 mg protein−1 in the late blastula stage and slightly lower values in the early and late pluteus stages. 相似文献
11.
Described here is a set of three-dimensional (3D) NMR experiments that rely on CACA-TOCSY magnetization transfer via the weak
3 \textJ\textCa\textCa ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} coupling. These pulse sequences, which resemble recently described 13C detected CACA-TOCSY (Takeuchi et al. 2010) experiments, are recorded in 1H2O, and use 1H excitation and detection. These experiments require alternate 13C-12C labeling together with perdeuteration, which allows utilizing the small
3 \textJ\textCa\textCa ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} scalar coupling that is otherwise masked by the stronger 1JCC couplings in uniformly 13C labeled samples. These new experiments provide a unique assignment ladder-mark that yields bidirectional supra-sequential
information and can readily straddle proline residues. Unlike the conventional HNCA experiment, which contains only sequential
information to the
1 3 \textCa ^{ 1 3} {\text{C}}^{\alpha } of the preceding residue, the 3D hnCA-TOCSY-caNH experiment can yield sequential correlations to alpha carbons in positions
i−1, i + 1 and i−2. Furthermore, the 3D hNca-TOCSY-caNH and Hnca-TOCSY-caNH experiments, which share the same magnetization pathway but use
a different chemical shift encoding, directly couple the 15N-1H spin pair of residue i to adjacent amide protons and nitrogens at positions i−2, i−1, i + 1 and i + 2, respectively. These new experimental features make protein backbone assignments more robust by reducing the degeneracy problem
associated with the conventional 3D NMR experiments. 相似文献
12.
Sérgio S. Thomasi Marcel O. Cerri Alberto C. Badino 《Bioprocess and biosystems engineering》2010,33(8):979-988
A method proposed in recent literature was applied to evaluate the average shear rate ( [(g)\dot]av ) \left( {\dot{\gamma }_{\rm av} } \right) in three pneumatic bioreactors of 5-dm3 working volume: bubble column, split airlift, and concentric-tube airlift. The volumetric oxygen transfer coefficient (k
L
a) is the appropriate characteristic parameter to assess the average shear rate ( [(g)\dot]av ) \left( {\dot{\gamma }_{\rm av} } \right) in this methodology. Correlations for [(g)\dot]av \dot{\gamma }_{\rm av} as a function of superficial gas velocity in the riser region (U
GR) and rheological fluid properties (consistency index, K, and flow index, n) were obtained for each model of pneumatic bioreactor studied. The [(g)\dot]av \dot{\gamma }_{\rm av} values estimated by the proposed methodology lay within the range of values calculated by classical correlations. The proposed
correlations were utilized to predict the [(g)\dot]av \dot{\gamma }_{\rm av} during the Streptomyces clavuligerus cultivations carried out at the same specific air flow rate (3.5 vvm) in the different types of pneumatic bioreactors. The
lowest values of [(g)\dot]av \dot{\gamma }_{\rm av} related to the highest values of consistency index (K) were found for the bubble column bioreactor, and the highest values of [(g)\dot]av \dot{\gamma }_{\rm av} related to the lowest values of K were found for the concentric-tube airlift bioreactor. Intermediate values were found for the split airlift bioreactor. The
results showed that high [(g)\dot]av \dot{\gamma }_{\rm av} values affect the structural health of the mycelia by the rupture of the hipha. 相似文献
13.
Two carotenoid 1,2-hydratase (CrtC) genes from the photosynthetic bacteria Rubrivivax gelatinosus and Thiocapsa roseopersicina were cloned and expressed in Escherichia coli in an active form and purified by affinity chromatography. The biochemical properties of the recombinant enzymes and their
substrate specificities were studied. The purified CrtCs catalyze cofactor independently the conversion of lycopene to 1-HO-
and 1,1′-(HO)2-lycopene. The optimal pH and temperature for hydratase activity was 8.0 and 30°C, respectively. The apparent K
m and V
max values obtained for the hydration of lycopene were 24 μM and 0.31 nmol h−1 mg−1 for RgCrtC and 9.5 μM and 0.15 nmol h−1 mg−1 for TrCrtC, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed two protein bands of 44 and
38 kDa for TrCrtC, which indicate protein processing. Both hydratases are also able to convert the unnatural substrate geranylgeraniol
(C20 substrate), which functionally resembles the natural substrate lycopene. 相似文献
14.
To gain insight into the metabolic design of the amino acid carrier systems in fish, we injected a bolus of 15N amino acids into the dorsal aorta in mature rainbow trout (Oncorhynchus mykiss). The plasma kinetic parameters including concentration, pool size, rate of disappearance (R
d), half-life and turnover rate were determined for 15 amino acids. When corrected for metabolic rate, the R
d values obtained for trout for most amino acids were largely comparable to human values, with the exception of glutamine (which
was lower) and threonine (which was higher). R
d values ranged from 0.9 μmol 100 g−1 h−1 (lysine) to 22.1 μmol 100 g−1 h−1 (threonine) with most values falling between 2 and 6 μmol 100 g−1 h−1. There was a significant correlation between R
d and the molar proportion of amino acids in rainbow trout whole body protein hydrolysate. Other kinetic parameters did not
correlate significantly with whole body amino acid composition. This indicates that an important design feature of the plasma-free
amino acids system involves proportional delivery of amino acids to tissues for protein synthesis. 相似文献
15.
CO2 efflux from soil and snow surfaces was measured continuously in a Japanese cedar (Cryptomeria japonica D. Don) forest in central Japan using an open dynamic chamber system. The chamber opens and closes automatically and records
measurements based on an open-flow dynamic method. Between May and December, mean soil CO2 efflux ranged from 1,529 mg CO2 m−2 h−1 in September to 255 mg CO2 m−2 h−1 in December. The seasonal change in CO2 efflux from the soil paralleled the seasonal pattern of soil temperature. No marked diurnal trends in soil CO2 efflux were observed on days without rainfall, whereas significant pulses in soil CO2 efflux were observed on days with rainfall. In this plantation, soil CO2 efflux frequently responded to rainfall. Measurements of changes from litter-covered soil to snow-covered surfaces revealed
that CO2 efflux decreased from values of ca. 250 mg CO2 m−2 h−1 above soil to less than 33 mg CO2 m−2 h−1 above snow. Soil temperature alone explained 66% of the overall variation in soil CO2 efflux, but explained approximately 85% of the variation when data from two anomalous periods were excluded. Moreover, we
found a significant correlation between soil CO2 efflux and soil moisture (which explained 44% of the overall variation) using a second-order polynomial function. Our results
suggest that the seasonality of CO2 efflux is affected not only by soil temperature and moisture, but also by drying and rewetting cycles and by litterfall pulses. 相似文献
16.
Kinetics of styrene biodegradation by <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. E-93486 总被引:1,自引:0,他引:1
The research into kinetics of styrene biodegradation by bacterial strain Pseudomonas sp. E-93486 coming from VTT Culture Collection (Finland) was presented in this work. Microbial growth tests in the presence
of styrene as the sole carbon and energy source were performed both in batch and continuous cultures. Batch experiments were
conducted for initial concentration of styrene in the liquid phase changed in the range of 5–90 g m−3. The Haldane model was found to be the best to fit the kinetic data, and the estimated constants of the equation were: μ
m = 0.1188 h−1, K
S = 5.984 mg l−1, and K
i = 156.6 mg l−1. The yield coefficient mean value
Y\textxs\textapp Y_{\text{xs}}^{\text{app}} for the batch culture was 0.72 gdry cells weight (gsubstrate)−1. The experiments conducted in a chemostat at various dilution rates (D = 0.035–0.1 h−1) made it possible to determine the value of the coefficient for maintenance metabolism m
d = 0.0165 h−1 and the maximum yield coefficient value
Y\textxs\textM = 0.913 Y_{\text{xs}}^{\text{M}} = 0.913 . Chemostat experiments confirmed the high value of yield coefficient
Y\textxs\textapp Y_{\text{xs}}^{\text{app}} observed in the batch culture. The conducted experiments showed high activity of the examined strain in the styrene biodegradation
process and a relatively low sensitivity to inhibition of its growth at higher concentrations of styrene in the solution.
Such exceptional features of Pseudomonas sp. E-93486 make this bacterial strain the perfect candidate for technical applications. 相似文献
17.
Kaarel Adamberg Petri-Jaan Lahtvee Kaspar Valgepea Kristo Abner Raivo Vilu 《Antonie van Leeuwenhoek》2009,95(3):219-226
Quasi steady state growth of Lactococcus
lactis IL 1403 was studied in glucose-limited A-stat cultivation experiments with acceleration rates (a) from 0.003 to 0.06 h−2 after initial stabilization of the cultures in chemostat at D = 0.2–0.3 h−1. It was shown that the high limit of quasi steady state growth rate depended on the acceleration rate used—at an acceleration
rate 0.003 h−2 the quasi steady state growth was observed until μ
crit = 0.59 h−1, which is also the μ
max value for the culture. Lower values of μ
crit were observed at higher acceleration rates. The steady state growth of bacteria stabilized at dilution rate 0.2 h−1 was immediately disrupted after initiating acceleration at the highest acceleration rate studied—0.06 h−2. Observation was made that differences [Δ(μ − D)] of the specific growth rates from pre-programmed dilution rates were the lowest using an acceleration rate of 0.003 h−2 (< 4% of preset changing growth rate). The adaptability of cells to follow preprogrammed growth rate was found to decrease
with increasing dilution rate—it was shown that lower acceleration rates should be applied at higher growth rates to maintain
the culture in the quasi steady state. The critical specific growth rate and the biomass yields based on glucose consumption
were higher if the medium contained S
0 = 5 g L−1 glucose instead of S
0 = 10 g L−1. It was assumed that this was due to the inhibitory effect of lactate accumulating at higher concentrations in the latter
cultures. Parallel A-stat experiments at the same acceleration and dilution rates showed good reproducibility—Δ(μ − D) was less than 5%, standard deviations of biomass yields per ATP produced (Y
ATP), and biomass yields per glucose consumed (Y
XS) were less than 15%. 相似文献
18.
Simultaneous measurements of chlorophyll (Chl) fluorescence and CO2 assimilation (A) in Vicia faba leaves were taken during the first weeks of growth to evaluate the protective effect of 24-epibrassinolide (EBR) against
damage caused by the application of the herbicide terbutryn (Terb) at pre-emergence. V. faba seeds were incubated for 24 h in EBR solutions (2 × 10−6 or 2 × 10−5 mM) and immediately sown. Terb was applied at recommended doses (1.47 or 1.96 kg ha−1) at pre-emergence. The highest dose of Terb strongly decreased CO2 assimilation, the maximum quantum yield of PSII photochemistry in the dark-adapted state (F
V/F
M), the nonphotochemical quenching (NPQ), and the effective quantum yield (ΔF/F′M) during the first 3–4 weeks after plant emergence. Moreover, Terb increased the basal quantum yield of nonphotochemical processes
(F
0/F
M), the degree of reaction center closure (1 − q
p), and the fraction of light absorbed in PSII antennae that was dissipated via thermal energy dissipation in the antennae
(1 − F′V/F′M). The herbicide also significantly reduced plant growth at the end of the experiment as well as plant length, dry weight,
and number of leaves. The application of EBR to V. faba seeds before sowing strongly diminished the effect of Terb on fluorescence parameters and CO2 assimilation, which recovered 13 days after plant emergence and showed values similar to those of control plants. The protective
effect of EBR on CO2 assimilation was detected at a photosynthetic photon flux density (PFD) of 650 μmol m−2 s−1 and the effect on ΔF/F′M and photosynthetic electron transport (J) was detected under actinic lightings up to 1750 μmol m−2 s−1. The highest dose of EBR also counteracted the decrease in plant growth caused by Terb, and plants registered the same growth
values as controls. 相似文献
19.
Soil temperature and biotic factors drive the seasonal variation of soil respiration in a maize (Zea mays L.) agricultural ecosystem 总被引:1,自引:0,他引:1
Guangxuan Han Guangsheng Zhou Zhenzhu Xu Yang Yang Jingli Liu Kuiqiao Shi 《Plant and Soil》2007,291(1-2):15-26
The diurnal and seasonal variation of soil respiration (SR) and their driving environmental factors were studied in a maize
ecosystem during the growing season 2005. The diurnal variation of SR showed asymmetric patterns, with the minimum occurring
around early morning and the maximum around 13:00 h. SR fluctuated greatly during the growing season. The mean SR rate was
3.16 μmol CO2 m−2 s−1, with a maximum of 4.87 μmol CO2 m−2 s−1 on July 28 and a minimum of 1.32 μmol CO2 m−2 s−1 on May 4. During the diurnal variation of SR, there was a significant exponential relationship between SR and soil temperature
(T) at 10 cm depth:
. At a seasonal scale, the coefficient α and β fluctuated because the biomass (B) increased α, and the net primary productivity (NPP) of maize markedly increased β of the exponential equation. Based on this, we developed the equation
to estimate the magnitude of SR and to simulate its temporal variation during the growth season of maize. Most of the temporal
variability (93%) in SR could be explained by the variations in soil temperature, biomass and NPP of maize. This model clearly
demonstrated that soil temperature, biomass and NPP of maize combined to drive the seasonal variation of SR during the growing
season. However, only taking into account the influence of soil temperature on SR, an exponential equation over- or underestimated
the magnitude of SR and resulted in an erroneous representation of the seasonal variation in SR. Our results highlighted the
importance of biotic factors for the estimation of SR during the growing season. It is suggested that the models of SR on
agricultural sites should not only take into account the influence of soil temperature, but also incorporate biotic factors
as they affect SR during the growing season. 相似文献
20.
The effects of nitric oxide (NO) on caulogenesis, shoot organogenesis and rhizogenesis from hypocotyl explants of Linum usitatissimum were investigated. Exogenously supplied NO donors, 5 μM sodium nitroprusside (SNP), 2 μM S-nitroso-N-acetylpenicillamine (SNAP) and 2 μM 3-morpholinosydnonimine (SIN-1), significantly promoted shoot differentiation from the
hypocotyl explants of L. usitatissimum excised from its in vitro raised seedlings. Potassium ferrocyanide, a structural analogue of SNP, lacking NO group, did not
promote shoot organogenesis. Likewise, products of NO,
\textNO2 - {\text{NO}}_{2}^{ - } and
\textNO3 - {\text{NO}}_{3}^{ - } supplied as 5 μM NaNO2 and 5 μM NaNO3 did not enhance shoot differentiation. Another source of NO, a mixture of sodium nitrite (SN) provided along with ascorbic
acid (AsA), also caused significant promotion in the average number of shoots per responding explant. SNP also augmented the
rhizogenic response of the microshoots in terms of percentage of responding explants, number of roots per responding explant
and average root length. The NO scavengers, 2-(4-carboxy-phenyl)-4, 4, 5, 5-tetramethylimideazoline-1-oxyl-3-oxide (cPTIO)
or methylene blue (MB), provided along with SNP, SNAP, SIN-1 or SN + AsA, at concentrations equimolar to the optimum concentration
of the donors, reversed the promotory influence, thereby, confirming the role of NO in promotion of in vitro morphogenesis.
However, NO scavengers individually did not affect the observed morphogenic processes. Morphological and histological studies
of hypocotyl segments cultured on BM or BM + SNP for 4, 8 and 12 days demonstrated that SNP enhanced shoot differentiation
by inducing a higher number of shoot primordia, each of which develops into a single shoot. 相似文献