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Liu R.,Tianjin Key Laboratory of Molecular Drug Research | Xu Y.,Key Laboratory of Original Agro environment Quality of Ministry of Agriculture | Jiang H.,CAS Institute of Zoology | Qiao C.,CAS Institute of Zoology | And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2014

The twin-arginine translocation (Tat) pathway exports folded proteins across the cytoplasmic membranes of bacteria and archaea. Two parallel Tat pathways (TatAdCd and TatAyCy systems) with distinct substrate specificities have previously been discovered in Bacillus subtilis. In this study, to secrete methyl parathion hydrolase (MPH) into the growth medium, the twin-arginine signal peptide of B. subtilis YwbN was used to target MPH to the Tat pathway of B. subtilis. Western blot analysis and MPH assays demonstrated that active MPH was secreted into the culture supernatant of wild-type cells. No MPH secretion occurred in a total-tat2 mutant, indicating that the observed export in wild-type cells was mediated exclusively by the Tat pathway. Export was fully blocked in a tatAyCy mutant. In contrast, the tatAdCd mutant was still capable of secreting MPH. These results indicated that the MPH secretion directed by the YwbN signal peptide was specifically mediated by the TatAyCy system. The N-terminal sequence of secreted MPH was determined as AAPQVR, demonstrating that the YwbN signal peptide had been processed correctly. This is the first report of functional secretion of a heterologous protein via the B. subtilis TatAyCy system. This study highlights the potential of the TatAyCy system to be used for secretion of other heterologous proteins in B. subtilis. © 2014 American Chemical Society.

Peng L.,Hunan Agricultural University | Zeng Q.,Hunan Agricultural University | Tie B.,Hunan Agricultural University | Lei M.,Hunan Agricultural University | And 4 more authors.
Journal of Colloid and Interface Science | Year: 2015

A MnO2 nanosheet (MnO2-NS) suspension was prepared from tetramethylammonium hydroxide (TMA{dot operator}OH), H2O2, and MnCl2{dot operator}4H2O, and its efficiency for Cd(II) removal from aqueous solutions was investigated. The maximum adsorption capacity of the MnO2-NS for Cd(II) was evaluated to be about 348mg/g, which is thus far the highest value reported for MnO2 at pH 6.0. This high adsorption capacity is attributed to efficient ion exchange. X-ray photoelectron spectroscopy (XPS) revealed that Cd(II) was adsorbed on MnO2 as CdO and Cd(OH)2. After Cd(II) adsorption, the suspended MnO2-NS aggregated and precipitated within 5.0min from solution. Therefore, dispersive MnO2-NS can be used to remove Cd(II) from wastewater rapidly and with high efficiency. © 2015 Elsevier Inc.

Li W.J.,ShenYang Agricultural University | Li W.J.,Agro Environmental Protection Institute | Li W.J.,Key Laboratory of Original Agro environment Quality of Ministry of Agriculture | Liu H.M.,Agro Environmental Protection Institute | And 12 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

Increases in atmospheric nitrogen deposition and changes in precipitation patterns are important phenomena related to changes in the global environment. These changes have created a series of increasingly serious ecological problems affecting the structure and function of grassland ecosystems. Therefore, grasslands have become a focus of ecological research in China and around the world in recent years. High nitrogen deposition can acidify grassland soils and lead to nutritional imbalances, decreases in biodiversity and productivity, and grassland degradation, all of which are serious threats to the function of grassland ecosystems. Precipitation can increase the efficiency of nitrogen fertilizer used by plants, and climate warming is accompanied by changes in precipitation. Studies of the interactive effects of nitrogen deposition and variation in rainfall on natural grassland ecosystems can help to increase our understanding of the responses of such ecosystems to changes in the global climate. In China, the Stipa baicalensis steppe, a type of meadow steppe, is mainly distributed in the forest steppe zone of the Songliao Plain and the east Inner Mongolian Plateau. In Inner Mongolia, farmers mainly use S. baicalensis steppe as natural pasture; therefore, it has an important role in livestock production. The aim of this study was to evaluate the responses of grassland plant community species diversity and the aboveground biomass of several common plant species to nitrogen deposition and irrigation. We set up a factorial experiment to test the interactive effects of eight nitrogen treatments and water addition in S. baicalensis steppe in Inner Mongolia in June 2010. This involved nitrogen (NH4NO3) application levels of 0 (the control treatment, CK), 15, 30, 50, 100, 150, 200, 300 kg N hm-2 a-1 (referred to as N0, N15, N30, N50, N100, N150, N200, N300, respectively) and simulated 100 mm summer rainfall. In mid-August 2013, we established 96 1 m ×1 m sample plots. The vegetation was harvested from each plot and the biomass of each species was measured to determine the effects of nitrogen and water addition on species diversity and the aboveground biomass of several common plants. Nitrogen and water application reduced plant species diversity in the steppe community, and there was a significant interaction effect between nitrogen and moisture. When water was added, increasing nitrogen application levels resulted in decreases in plant species richness, Shannon-Wiener index, and Pielou evenness index. When water was not added, increasing nitrogen application levels resulted in changes in species richness, Shannon- Wiener index, and Pielou evenness index that showed a “single-peak”, but overall downward trend. Plant species differed in their responses to nitrogen and water addition. With increasing nitrogen application levels, the aboveground biomass of Leymus chinensis increased significantly, reaching a maximum at N300; the aboveground biomass of S. baicalensis, Achnatherum sibiricum, Cleistogenes squarrosa, Carex duriuscula, and Artemisia frigida first increased and then decreased, showing a “single-peak”trend; and the aboveground biomass of Potentilla acaulis, Thermopsis lanceolata, Melilotoides ruthenica, and Filifolium sibiricum decreased gradually. There was a significant interaction effect between water and nitrogen application level on the biomass of S. baicalensis, A. sibiricum, and M. ruthenica. We concluded that the changes in plant species diversity and aboveground biomass were related to nutrient application levels, water availability, their own characteristics, and interspecific and intraspecific competition. © 2015, Ecological Society of China. All rights reserved.

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