Characterization of Phenol Biodegradation by Comamonas testosteroni ZD4-1 and Pseudomonas aeruginosa ZD4-3

To investigate the characteristic and biochemical mechanism about the phenol biodegradation by bacterial strains ZD 4-1 and ZD 4-3. Methods Bacterial strains ZD 4-1 and ZD 4-3 were isolated by using phenol as the sole source of carbon and energy, and identified by 16S rDNA sequence analysis. The concentrations of phenol and total organic carbon (TOC) were monitored to explore the degradation mechanism. The biodegradation intermediates were scanned at 375 nm by using a uv-vis spectrophotometer. The enzyme assays were performed to detect the activities of dioxygenases. Results Bacterial strains ZD 4-1 and ZD 4-3 were identified as Comamonas testosteroni and Pseudomonas aeruginosa by 16S rDNA sequence analysis, respectively. The growth of the two strains was observed on a variety of aromatic hydrocarbons. The strains ZD 4-1 and ZD 4-3 metabolized phenol via ortho-pathways and meta-pathways, respectively. In addition, the results of enzyme assays showed that the biodegradation efficiency of phenol by meta-pathways was higher than that by ortho-pathways. Finally, the results of induction experiment indicated that the catechol dioxygenases, both catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O), were all inducible. Conclusion The strains ZD 4-1 and ZD 4-3 metabolize phenol through ortho-pathways and meta-pathway, respectively. Furthermore, the biodegradation efficiency of phenol by meta-pathways is higher than that by ortho-pathways.

Effects of 60-day NO_2 fumigation on growth,oxidative stress and antioxidative response in Cinnamomum camphora seedlings

Objective： To study the oxidative stress and antioxidative response of Cinnamomum camphora seedlings exposed to nitrogen dioxide （NO2） fumigation. Methods： Measurements were made up of the growth, chlorophyll content, chlorophyll fluorescence, antioxidant system and lipid peroxidation of one-year-old C. camphora seedlings exposed to NO2 （0.1, 0.5, and 4 μl/L） fumigation in open top chambers over a period of 60 d. Results： After the first 30 d, 0.5 and 4.0 μl/L NO2 showed insignificant effects on the growth of C. camphora seedlings. However, exposure to 0.5 and 4.0 pilL NO2 for 15 d significantly reduced their chlorophyll content （P〈0.05）, enhanced their malondialdehyde （MDA） content and superoxide dismutase （SOD） activity （P〈0.05）, and also significantly reduced the maximal quantum yield of PSII in the dark [the ratio of variable fluorescence to maximal fluorescence （Fv/Fm）] （P〈0.05）. In the latter 30 d, 0.5μl/L NO2 showed a positive effect on the vitality of the seedlings, which was reflected by a recovery in the ratio of Fv/Fm and chlorophyll content, and obviously enhanced growth, SOD activity, ascorbate （AsA） content and glutathione reductase （GR） activity （P〈0.05）; 4.0 pilL NO2 then showed a negative effect, indicated by significant reductions in chlorophyll content and the ratio of Fv/Fm, and inhibited growth （P〈0.05）. Conclusion： The results suggest adaptation of C. camphora seedlings to 60-d exposure to 0.1 and 0.5 μl/L NO2, but not to 60-d exposure to 4.0 pilL NO2 C. camphora seedlings may protect themselves from injury by strengthening their antioxidant system in response to NO2-induced oxidative stress.

Protein Changes in Response to Pyrene Stress in Maize （Zea mays L.） Leaves

Phytoremedlation is a relatively new approach to remove polycyclic aromatic hydrocarbons （PAHs） from the environment. When plants are grown under pyrene treatment, they respond by synthesizing a set of protective proteins. To learn more about protein changes in response to pyrene treatment, we extracted total proteins from the leaves of maize （Zea mays L.） 1 week after pyrene treatment. The proteins extracted were separated with twodimensional gel electrophoresis. In total, approximately 54 protein spots were found by comparing gels from treated and control groups. According to the Isoelectric point, molecular weight, and abundance of these protein spots, 20 pyrene-lnduced proteins were found to have changed abundance. Of these, 15 protein spots were Increased and five protein spots were newly appeared in pyrene-treated plant leaves. Six model upregulated protein spots of different molecular weights were excised from the gels and subjected to trypsin digestion followed by peptide separation using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Peptlde masses were used to search the matrix-science database for protein Identification. Two of the proteins were Identified on the basis of the homology of their peptide profiles with existing protein sequences as pyruvate orthophosphate diklnase and the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunlt. These proteins are Involved in the regulation of carbohydrate and energy metabolism. The present study gives new Insights into the pyrene stress response In maize leaves and demonstrates the power of the proteomlc approach in phytoremedlation of PAHs.

Fertilization increases paddy soil organic carbon density

Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon(SOC) sequestration.We sampled soils from a long-term(25 years) paddy experiment in subtropical China.The experiment included eight treatments:(1) check,(2) PK,(3) NP,(4) NK,(5) NPK,(6) 7F:3M(N,P,K inorganic fertilizers+30% organic N),(7) 5F:5M(N,P,K inorganic fertilizers+50% organic N),(8) 3F:7M(N,P,K inorganic fertilizers+70% or-ganic N).Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment.The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha.The SOC densities of all fertilizer treatments were greater than that of the check.Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers.The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues.Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization.Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC.