Biosorption of Cd, Cu, Pb, and Zn from aqueous solutions by the fruiting bodies of jelly fungi (Tremella fuciformis and Auricularia polytricha)

In this study, dried and humid fruiting bodies of Tremella fuciformis and Auricularia polytricha were examined as cost-effective biosorbents in treatment of heavy metals (Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺) in aqueous solution. The humid T. fuciformis showed the highest capacity to adsorb the four metals in the multi-metal solutions. The Pb²⁺ adsorption rates were 85.5%, 97.8%, 84.8%, and 91.0% by dried T. fuciformis, humid T. fuciformis, dried A. polytricha, and humid A. polytricha, respectively. The adsorption amount of Pb²⁺ by dried and humid T. fuciformis in Cd²⁺ + Pb²⁺, Cu²⁺ + Pb²⁺, Pb²⁺ + Zn²⁺, Cd²⁺ + Cu²⁺ + Pb²⁺, and Cd²⁺ + Zn²⁺ + Pb²⁺ solutions were not lower than that in Pb²⁺ solutions. The results suggested that in humid T. fuciformis, Cd²⁺, Cu²⁺, and Zn²⁺ promoted the Pb²⁺ adsorption by the biomass. In the multi-metal solutions of Cd²⁺ + Cu²⁺ + Pb²⁺ + Zn²⁺, the adsorption amount and rates of the metals by all the test biosorbents were in the order of Pb²⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺. Compared with the pseudo first-order model, the pseudo second-order model described the adsorption kinetics much better, indicating a two-step biosorption process. The present study confirmed that fruiting bodies of the jelly fungi should be useful for the treatment of wastewater containing Cd²⁺, Cu²⁺, Pb²⁺, and Zn²⁺.     

Characterization of depth-related bacterial communities and their relationships with the environmental factors in the river sediments

To better understand the bacterial processes in river sediments, it is necessary to investigate the depth-related bacterial communities in the whole sediment profile. Sediment samples were collected to a depth of 25 cm from the Pearl River. Bacterial abundance, activity, cell-specific respiration rate, and diversity were measured, respectively, by 4′, 6-diamidino-2-phenylindole direct count, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) staining, electron transport system by CTC reduction, and denaturing gradient gel electrophoresis analysis of 16S rRNA amplification fragments. Results showed that the bacterial metabolism activities decreased with the sediment depth. The total bacterial abundance was highest in the surface sediment with 65.1 × 10⁷ cells g⁻¹, and decreased to 11.1 × 10⁷ cells g⁻¹ below 20 cm in the sample location that suffered from heavy sewage inputs. The active bacteria accounted for 7.50–46.7% of the total bacterial number and decreased with the sediment depth. Electron transport system by the CTC reduction showed that bacterial respiration rate declined from 1.093 μmol CTC-formazan h⁻¹ g⁻¹ in the surface sediment to a half in the bottom sediment, while the cell-specific respiration increased significantly with the depth from 3.56 to 93.75 fmol CTC-formazan cell⁻¹. The bacterial diversity also changed with the depth. Beta-Proteobacteria were the dominant species in the surface sediment, whereas Delta-Proteobacteria were the main species below 10 cm. Results of canonical correspondence analysis (CCA) indicated that the distribution of bacteria was affected by the combined effect of various dissolved inorganic matter, while the respiration rate was independent of the nutrient conditions. The specific bacterial distribution contributed to not only the nutrient cycle but also enhanced pollutant decomposition in sediment of the Pearl River. The results showed that some specific bacterial species had a strong activity in the deeper layers. Therefore, the metabolic functions of the deeper bacterial species should not be neglected.     

Root length density and water uptake distributions of winter wheat under sub-irrigation

As the critical information to study flow transport in soil–plant systems, root distributions and root-water-uptake (RWU) patterns have been studied extensively. However, most root distribution data in the past were collected under surface irrigation. Less research has been conducted to characterize root distributions under sub-irrigation. The objectives of this study were to (1) test if the generalized function of normalized root length density (NRLD) in the literature was applicable to root distributions of winter wheat under natural sub-irrigation, which provides water from subsurface by capillary rise from the water table, and (2) estimate RWU distributions of winter wheat under natural sub-irrigation. Column experiments were conducted to study the distributions of root length density (RLD) and RWU of winter wheat (Triticum aestivum L. cv. Nongda 189) during a growing period of 57 days from planting to tillering stages under surface irrigation and natural sub-irrigation. Data of root distributions and soil water content were collected in the experiments with different treatments of irrigation levels. Results showed that the RLD distributions of winter wheat under both surface irrigation and natural sub-irrigation were of similar patterns. The NRLD distributions under sub-irrigation were adequately characterized by the generalized function. An inverse method was employed to estimate the average RWU rate distributions of winter wheat. In addition, based on the potential RWU coefficient and the NRLD function, a simple approach was developed to predict RWU rates at different depths. The predicted RWU rates had a good agreement with the estimated RWU rate distributions using the inverse method.Section editor: R. E. Munns     

Modeling soil water movement with water uptake by roots

Soil water movement with root water uptake is a key process for plant growth and transport of water and chemicals in the soil-plant system. In this study, a root water extraction model was developed to incorporate the effect of soil water deficit and plant root distributions on plant transpiration of annual crops. For several annual crops, normalized root density distribution functions were established to characterize the relative distributions of root density at different growth stages. The ratio of actual to potential cumulative transpiration was used to determine plant leaf area index under water stress from measurements of plant leaf area index at optimal soil water condition. The root water uptake model was implemented in a numerical model. The numerical model was applied to simulate soil water movement with root water uptake and simulation results were compared with field experimental data. The simulated soil matric potential, soil water content and cumulative evapotranspiration had reasonable agreement with the measured data. Potentially the numerical model implemented with the root water extraction model is a useful tool to study various problems related to flow transport with plant water uptake in variably saturated soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Surface display of ACC deaminase on endophytic <Emphasis Type="Italic">Enterobacteriaceae</Emphasis> strains to increase saline resistance of host rice sprouts by regulating plant ethylene synthesis

Background

Most endophytic bacteria in consortia, which provide robust and broad metabolic capacity, are attractive for applications in plant metabolic engineering. The aim of this study was to investigate the effects of engineered endophytic bacterial strains on rice sprout ethylene level and growth under saline stress. A protocol was developed to synthesize engineered strains by expressing bacterial 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene on cells of endophytic Enterobacter sp. E5 and Kosakonia sp. S1 (denoted as E5P and S1P, respectively).

Results

Results showed that ACC deaminase activities of the engineered strains E5P and S1P were significantly higher than those of the wild strains E5 and S1. About 32–41% deaminase was expressed on the surface of the engineered strains. Compared with the controls without inoculation, inoculation with the wild and engineered strains increased the deaminase activities of sprouts. Inoculation with the engineered strains increased 15–21% more deaminase activities of sprouts than with the wild strains, and reduced the ethylene concentrations of sprouts more significantly than with wild strains (P < 0.05). Inoculation with the wild and engineered strains promoted the growth of sprouts, while the promoting effects were more profound with the engineered strains than with the wild strains. The engineered strains improved saline resistance of sprouts under salt concentrations from 10 to 25 g L^?1. The engineered strains promoted longer roots and shoots than the wild strains under the salt stresses, indicating that the ACC deaminases on the endophytic bacterial cells could result in plant-produced ACC degradation and inhibit plant ethylene formation.

Conclusions

The protocols of expressing enzymes on endophytic bacterial cells showed greater potentials than those of plant over-expressed enzymes to increase the efficiency of plant metabolic pathways.

     

Removal of Cr(VI) from aqueous solutions by fruiting bodies of the jelly fungus (Auricularia polytricha)

The aim of this study was to investigate the potential to remove chromium (Cr) from aqueous solutions using the fruiting body of Auricularia polytricha. Batch experiments were conducted under various conditions, and different models were used to characterize the biosorption process. Results showed that, for both fresh and dried fruiting bodies of A. polytricha, removal efficiencies of Cr(VI) and total Cr reached maximum values at pH values of 1 and 2, respectively. The process of Cr(VI) removal by A. polytricha included the sorption process as well as the reduction of Cr(VI) to Cr(III). Spectra of X-ray photoelectron spectroscopy of the biosorbent revealed that most of the Cr loaded on the biomass surface was in the trivalent form. The Freundlich model fitted the isotherm process better than the Langmuir model in the concentration range examined. The pseudo-second-order model well described the adsorption process of Cr onto the biomass. The biosorption capacity of Cr(VI) by fruiting bodies was much higher than that by most of other biosorbents reported. The results suggest that the fruiting bodies of A. polytricha should be a promising biomaterial for Cr removal from water contaminated by the heavy metal.     

全球陆地生态系统光合作用与呼吸作用的温度敏感性

基于全球647套通量数据,定量分析了全球尺度下生态系统光合作用和呼吸作用的温度敏感性(Q10)随纬度、气候和植被的分布规律。结果表明:在全球尺度下,光合作用和呼吸过程的温度敏感性(Q10,G和Q10,R)都随纬度的升高而增加,其中Q10,G和Q10,R的均值分别为3.99±0.21和2.28±0.074。除热带多树草原、常绿落叶林外,Q10,G均大于Q10,R值。不同植被类型的温度敏感性存在显著性差异,表现为:针叶林阔叶林;落叶林常绿林,其中生态系统的季节性变异是造成差异的主要原因。当植被类型和纬度区域共同影响Q10值时,植被类型对Q10值的总变异贡献更大。气候类型对Q10,G和Q10,R都有显著影响。在气候带上,干旱带的Q10,G最小,而冷温带的Q10,G最高。不同气候类型下(除温带草原气候外)的Q10,G都大于Q10,R。在极端条件下,温度可能不在是主导因素,而水分对温度敏感性的影响不可忽略,今后的研究需要更多的关注生态系统温度敏感性对水分变化的响应。     

Empirical Models Estimating Carbon Dioxide Accumulation in Two Petroleum Hydrocarbon–Contaminated Soils

Bioremediation is a popular method in degrading diesel fuel contaminants from soil. Bioremediation can be enhanced by estimating the effect of important environmental parameters on microbial activity. Respirometry was used to develop empirical models describing the effects of temperature, moisture, nitrogen, and phosphorus concentration on microbial activity in a diesel-contaminated soil from Wyoming. Carbon dioxide (CO₂) data were analyzed using a base equation where its coefficient values were functions of each parameter. Two physiologically different groups of microorganisms were identified from the results under different operating temperatures. The empirical correlations were combined into one model and this model was tested against a hydrocarbon-contaminated soil collected from a site in Egypt with similar history of contamination. The predicted CO₂ evolution agreed well with the actual data obtained from the Egyptian soil samples, showing a sound predicting power of the empirical model for petroleum hydrocarbon biodegradation. Overall, the empirical correlations developed from the respirometric data provide a method to describe microbial activity in diesel-contaminated soils.     

Studies on "stiffness of extremities disease" in the yak (Bos mutus)

Wild yak (Bos mutus) are affected by a disorder known colloquially as "stiffness of extremities disease," characterized by emaciation, lameness, stiffness in the gait, enlargement of the costochondral junctions, and abnormal curvature in the long bones. Results from preliminary epidemiologic and clinical observations suggested that this was a local, nutritional and metabolic disease associated with some mineral deficiency. Our objective was to determine the possible relationship between this disease and phosphorus (P) deficiency. We found that P concentrations in forage samples from affected areas were significantly lower than were those from unaffected areas, and the mean calcium:P ratio in the affected forage was 14:1. Phosphorus concentrations of blood, bone, teeth, and hair from affected yak were also significantly lower than were those from reference yak. Serum P levels of affected animals were much lower than were those of reference yak, whereas serum alkaline phosphatase levels were significantly higher than were those from reference yak. The P deficiency disease could be cured with supplement of disodium hydrogen phosphate (Na(2)HPO(4)). We conclude that the disease is mainly caused by P deficiency in forage.