Two new antibacterial sesquiterpenoids from Centipeda minima

Two new guaiane-type sesquiterpene lactones, compounds 1 and 2, along with three known guaianolide- or pseudoguaianolides, were isolated from Centipeda minima (whole plant). Their structures were identified by spectroscopic and mass-spectrometric analyses. The configuration at C5 of the guaiane framework of 1 was rationalized by quantum-mechanical calculations (Table 2). All compounds were found to be active against eight different microbial pathogens (Table 3), with MIC values in the range of 6.25-100 microg/ml.     

Characterization of functional microbial community in a membrane-aerated biofilm reactor operated for completely autotrophic nitrogen removal

The 16S rDNA-based molecular technique was applied to investigate the functional microbial community of a membrane-aerated biofilm (MAB) that was used for completely autotrophic nitrogen removal over nitrite (CANON). The relationships among two kinds of key bacteria responsible for CANON: aerobic ammonia-oxidizing bacteria (AOB) and Anammox bacteria, and their possible distributions in the MAB were discussed based on the microbial community analysis. FISH analysis showed the existence of two visible active layers in experimental MAB. One is the partial nitrifying layer located in the region of oxygen-rich membrane-biofilm interface, dominated by NSO190-positive AOB. The other is the Anammox active layer located in the region of anoxic liquid-biofilm interface, dominated by PLA46 and AMX820-positive Anammox microorganisms. As a result of this study, the AOB as well as Anammox bacteria were present and active in experimental MABR, and the cooperation between AOB and Anammox bacteria was considered to be responsible for CANON.     

Sensitization enhancement of europium in ZnSe/ZnS core/shell quantum dots induced by efficient energy transfer

Eu‐doped ZnSe:/ZnS quantum dots (formed as ZnSe:Eu/ZnS QDs) were successfully synthesized by a two‐step wet chemical method: nucleation doping and epitaxial shell growing. The sensitization characteristics of Eu‐doped ZnSe and ZnSe/ZnS core/shell QD are studied in detail using photoluminescence (PL), PL excitation spectra (PLE) and time‐resolved PL spectroscopy. The emission intensity of Eu ions is enhanced and that of ZnSe QDs is decreased, implying that energy was transferred from the excited ZnSe host materials (the donor) to the doped Eu ions (the acceptor). PLE reveals that the ZnSe QDs act as an antenna for the sensitization of Eu ions through an energy transfer process. The dynamics of ZnSe:Eu/ZnS core/shell quantum dots with different shell thicknesses and doping concentrations are studied via PL spectra and fluorescence lifetime spectra. The maximum phosphorescence efficiency is obtained when the doping concentration of Eu is approximately 6% and the sample showed strong white light under ultraviolet lamp illumination. By surface modification with ZnS shell layer, the intensity of Eu‐related PL emission is increased approximately three times compared with that of pure ZnSe:Eu QDs. The emission intensity and wavelength of ZnSe:Eu/ZnS core/shell quantum dots can be modulated by different shell thickness and doping concentration. The results provide a valuable insight into the doping control for practical applications in laser, light‐emitting diodes and in the field of biotechnology. Copyright © 2014 John Wiley & Sons, Ltd.     

Purification and characterization of a fibrinolytic enzyme of Bacillus subtilis DC33, isolated from Chinese traditional Douchi

Bacillus subtilis DC33 producing a novel fibrinolytic enzyme was isolated from Ba-bao Douchi, a traditional soybean-fermented food in China. The strong fibrin-specific enzyme subtilisin FS33 was purified to electrophoretic homogeneity using the combination of various chromatographic steps. The optimum temperature, pH value, and pI of subtilisin FS33 were 55°C, 8.0, and 8.7, respectively. The molecular weight was 30 kDa measured by SDS–PAGE under both reducing and non-reducing conditions. The enzyme showed a level of fibrinolytic activity that was about six times higher than that of subtilisin Carlsberg. The first 15 amino acid residues of N-terminal sequence of the enzyme were A-Q-S-V-P-Y-G-I-P-Q-I-K-A-P-A, which are different from that of other known fibrinolytic enzymes. The amidolytic activities of subtilisin FS33 were inhibited completely by 5 mM phenylmethanesulfonyl fluoride (PMSF) and 1 mM soybean trypsin inhibitor (SBTI), but 1,4-dithiothreitol (DTT), β-mercaptoethanol, and p-hydroxymercuribenzoate (PHMB) did not affect the enzyme activity; serine and tryptophan are thus essential in the active site of the enzyme. The highest affinity of subtilisin FS33 was towards N-Succ-Ala-Ala-Pro-Phe-pNA. Therefore, the enzyme was considered to be a subtilisin-like serine protease. The fibrinolytic enzyme had a high degrading activity for the Bβ-chains and Aα-chain of fibrin(ogen), and also acted on thrombotic and fibrinolytic factors of blood, such as plasminogen, urokinase, thrombin, and kallikrein. So subtilisin FS33 was able to degrade fibrin clots in two ways, i.e., (a) by forming active plasmin from plasminogen and (b) by direct fibrinolysis.     

Diversity of centromeric repeats in two closely related wild rice species, Oryza officinalis and Oryza rhizomatis

Oryza officinalis (CC, 2n=24) and Oryza rhizomatis (CC, 2n=24) belong to the Oryza genus, which contains more than 20 identified wild rice species. Although much has been known about the molecular composition and organization of centromeres in Oryza sativa, relatively little is known of its wild relatives. In the present study, we isolated and characterized a 126-bp centromeric satellite (CentO-C) from three bacterial artificial chromosomes of O. officinalis. In addition to CentO-C, low abundance of CentO satellites is also present in O. officinalis. In order to determine the chromosomal locations and distributions of CentO-C (126-bp), CentO (155 bp) and TrsC (366 bp) satellite within O. officinalis, fluorescence in situ hybridization examination was done on pachytene or metaphase I chromosomes. We found that only ten centromeres (excluding centromere 7 and 2) contain CentO-C arrays in O. officinalis, while centromere 7 comprises CentO satellites, and centromere 2 is devoid of any detectable satellites. For TrsC satellites, it was detected at multiple subtelomeric regions in O. officinalis, however, in O. rhizomatis, TrsC sequences were detected both in the four centromeric regions (CEN 3, 4, 10, 11) and the multiple subtelomeric regions. Therefore, these data reveal the evolutionary diversification pattern of centromere DNA within/or between close related species, and could provide an insight into the dynamic evolutionary processes of rice centromere.     

Highly efficient expression and purification system of small-size protein domains in Escherichia coli for biochemical characterization

It is often essential to focus the study on the small-size domains of large proteins in eukaryotic cells in the post-genomic era, but the low expression level, insolubility, and instability of the domains have been continuing to hinder the massive purification of domain peptides for structural and biological investigation. In this work, a highly efficient expression and purification system based on a small-size fusion partner GB1 and histidine tag was utilized to solve these problems. Two vectors, namely pGBTNH and pGBH, were constructed to improve expression and facilitate purification. The linker and thrombin cleavage site have been optimized for minimal degradation during purification process. This system has been tested for eight domain peptides varying in size, linker, hydrophobicity, and predicted secondary structure. The results indicate that this system is achievable to produce these domain peptides with high solubility and stability for further biochemical characterization. Moreover, the fusion protein without the linker and thrombin cleavage site is also suitable for spectroscopic studies especially for NMR structural elucidation, if the target peptide is prone to precipitation or easily degraded during purification. This system will be beneficial to the research field of structure and function of small domain and peptide fragment.     

Integrative taxonomy recognized a new cryptic species within Stipa grandis from Loess Plateau of China

Stipa shanxiensis, a cryptic species within Stipa grandis that originated from central and western China, is described based on morphological, genomic, and ecological data from field and common garden experiments. Stipa shanxiensis morphologically resembles S. grandis, although phylogenetically it is closely related to the less morphologically similar Stipa baicalensis and Stipa krylovii. Of the eight significant morphological differences between S. shanxiensis and S. grandis, the two, cauline ligules longer than 2 cm with a filiform apex, and hairs shorter than 0.2 mm on the adaxial surface of the cauline uppermost leaves can be used to distinguish the species. Results from a common garden experiment verified that the two diagnostic characteristics were relatively stable and less morphologically plastic in response to environmental variation. Furthermore, a significant ecological divergence was found between S. shanxiensis and S. grandis, such that the former preferred warmer and more humid climates, and their predicted distribution was generally separated. Taken together, our results highlight that the integrative taxonomic approach was valuable for recognizing a new cryptic species in Stipa. In particular, we find that common garden experiments involving the effects of growth stage and characteristic position helped to morphologically diagnose cryptic species. These findings may also facilitate our understandings of ecological adaption and phenotypic plasticity in response to environmental change.     

Possible role of the CYC2c gene in the cornflower-like ray floret phenotype of Gaillardia cultivars

Journal of Plant Research - Gaillardia plants have been widely cultivated in China and have become an important component of garden landscaping. Different from the common ligulate ray floret, the...     

High endemicity of alveolar echinococcosis in Yili Prefecture,Xinjiang Autonomous Region,the People’s Republic of China: Infection status in different ethnic communities and in small mammals

Alveolar echinococcosis (AE) is a life-threatening disease in humans caused by the larval stage of Echinococcus multilocularis. The tapeworm is transmitted between small mammals and dogs/foxes in the Northern Hemisphere. In this study 286 AE cases were reported from eight counties and one city in Yili Prefecture, Xinjiang Autonomous Region, the People’s Republic of China from 1989 to 2015 with an annual incidence (AI) of 0.41/100,000. Among the patients, 73.08% were diagnosed in the last 11 years. Four counties in the high mountainous areas showed higher AI (0.51–1.22 cases/100,000 residents) than the four counties in low level areas (0.19–0.29/100,000 residents). The AI of AE in Mongolian (2.06/100,000 residents) and Kazak (0.93/100,000 residents) ethnic groups was higher than the incidence in other ethnic groups indicating sheep-farming is a risk for infection given this activity is mainly practiced by these two groups in the prefecture. A total of 1411 small mammals were captured with 9.14% infected with E. multilocularis metacestodes. Microtus obscurus was the dominant species in the mountain pasture areas with 15.01% of the voles infected, whereas Mus musculus and Apodemus sylvaticus were the dominant small mammals in the low altitude areas. Only 0.40% of A. sylvaticus were infected with E. multilocularis. PCR amplification and sequencing analysis of the mitochondrial cox1 gene showed that E. multilocularis DNA sequences from the small mammals were identical to isolates of local human AE cases. The overall results show that Yili Prefecture is a highly endemic area for AE and that the high-altitude pasture areas favorable for M. obscurus may play an important role in its transmission in this region.