[Fabrication and evaluation of the enzyme immunosensor for rapid detection of Vibrio parahaemolyticus based on chitosan-SiO2 hybrid membrane].

OBJECTIVE: To improve the key technology of immunesensors in immobilizing bio-sensitive element and keeping its bioactivity, an enzyme immunosensor based on chitosan-SiO(2) (CS-Sio(2)) hybrid membrane was fabricated. To estimate the new immunosensor Vibrio parahaemolyticus which was the main pathogens of aquatic products. METHODS: A CS-SiO(2) hybrid membrane was prepared using sol-gel method. The enzyme immunosensor was fabricated by coating the membrane and horseradish peroxidase labeled Vibrio parahaemolyticus antibody (HRP-anti-VP) on the surface of four-channel screen-printed carbon electrode. The immunosensor was characterized by cyclic voltammetry. Vibrio parahaemolyticus could be detected according to the decrease percentage (DP) of peak current before and after immune response, while cyclic voltammetry was used as an electrochemical mean to detect the products of the enzymatic reaction. Seven kinds of bacteria, like Vibrio alginolyticus, were selected for specific experiments. RESULTS: By studying the infrared spectrum of three kinds of films, the CS-SiO(2) hybrid membrane was prepared and HRP-anti-VP was fixed in the hybrid membrane. Under the optimum conditions of immunoreaction and electrochemical detection, the DP of peak current before and after immune response showed a linear relation with lgC in the range of 10(4) - 10(9) cfu/ml, while the linear regression equation was: DP = 6.5 lgC-3.319, the correlation coefficient was 0.9958 and the detection limit was 6.9 x 10(3) cfu/ml (S/N = 3). The immunosensor possessed acceptable specificity, reproducibility (RSD < 6%), stability (the amperometric response was 95% of the initial response after a week) and accuracy (96.7% of the results obtained by the immunosensor were in agreement with those obtained by GB/T 4789.7-2003). CONCLUSION: The enzyme immunosensor based on CS-SiO(2) hybrid membrane gave a good performance in rapid detection of Vibrio parahaemolyticus.

[Effects of elevated atmospheric CO2 concentration and nitrogen addition on the growth of Calamagrostis angustifolia in Sanjiang Plain freshwater marsh].

By using open top chamber, an experiment with two levels of atmospheric CO2 concentration (350 and 700 micromol x mol(-1)) and three levels of nitrogen supply (0, 5, and 15 g N x m(-2)) was conducted to investigate the effects of elevated atmospheric CO2 and nitrogen supply on the growth of Calamagrostis angustifolia in the freshwater marsh of Sanjiang Plain. Under elevated atmospheric CO2 concentration, the phenophase of C. angustifolia advanced. Jointing stage was advanced by 1-2 d, and maturity stage was advanced by 3 d. Elevated atmospheric CO2 promoted the tillering of C. angustifolia, with the increment of tiller number under 0, 5, and 15 g x m(-2) of nitrogen supply being 8.2% (P < 0.05), 8.4% (P < 0.05), and 5.5% (P > 0.05), respectively. Elevated atmospheric CO2 also promoted the aboveground biomass at jointing and heading stages, the increment being 12.4% and 20.9% (P < 0.05), respectively, and increased the belowground biomass at later growth stages, with the increment at dough stage and maturity stage being 20.5% and 20.9% (P < 0.05), respectively. The responses of C. angustifolia biomass to elevated atmospheric CO2 concentration depended on nitrogen supply level. Under sufficient nitrogen supply, the promotion effect of elevated atmospheric CO2 concentration on the biomass of C. angustifolia was higher.

[Effects of simulated soil warming on the growth and physiological characters of Deyeuxia angustifolia].

By using improved heating cables, a field experiment was conducted to study the effects of 1 degrees C-30 degrees C soil warming on the growth and physiological characters of Deyeuxia angustifolia. Soil warming obviously promoted the growth of D. angustifolia. Under flooded condition, the plant height increased by 18.2%, leaf area increased by 37.32%, root volume increased by 24.67%, total root absorbing area increased by 60% , and tillers number increased by 25.81%; under unflooded condition, the plant height increased by 12.09%, leaf area increased by 32.9%, root volume increased by 36.26%, total root absorbing area increased by 37.47%, and tillers number increased by 32.77%. The responses of D. angustifolia physiological indices to soil warming were more obvious under flooded than under un-flooded condition. Under flooded condition, the total chlorophyll content and root soluble protein content increased by 9.8% and 23.88%, while the leaf soluble protein and soluble carbon contents and root soluble carbon content decreased by 25.02%, 22.92%, and 35.23%, respectively. 1 degrees C-30 degrees C soil warming promoted the growth of D. angustifolia, but the responses of its physiological characters to the soil warming varied with water conditions.

[Effects of simulated nitrogen deposition on biomass of wetland plant and soil active carbon pool].

A simulation study was made on the responses of biomass of Deyeuxia angustifolia and soil active carbon pool in Sanjiang Plain of Northeast China to simulated nitrogen deposition. Two water conditions (W1: non-flooded, W2: flooded) and four N treatments (equivalent to 0, 1, 3, 5 g N x m(-2) x a(-1) nitrogen deposition rate) were installed. The results showed that under effects of nitrogen deposition, the total biomass, above-ground biomass, and root biomass of D. angustifolia were higher than the control, and the increment of root biomass was the highest. Both the carbon content and its allocation proportion in D. angustifolia root increased significantly, while the carbon content in above-ground part decreased dramatically (P < 0.05). Nitrogen deposition also had significant effects on soil active carbon pools, and the contents of various fractions in the carbon pool were the highest in treatment 5 g N x m(-2) x a(-1). The responses of various fractions in soil active carbon pool to nitrogen deposition followed the sequence of carbohydrate carbon > labile carbon > dissolved organic carbon > microbial biomass carbon, and the interaction between nitrogen deposition and flooded water condition facilitated the release of soil active carbon. Regression analysis indicated that there were significant correlations between soil active carbon pools and plant indices of D. angustifolia. Nitrogen deposition could enhance the biomass of D. angustifoliat and soil active carbon content.