A new mechanism of invader success： Exotic plant inhibits natural vegetation restoration by changing soil microbe community

Since the 1950s of the last century, the exotic plant, Eupatorium adenophorum, has spread rapidly across southwest China, damaging native ecosystems and causing great economic losses. We examined the pH, N, P, K, and organic matter concentrations, and the bacterial community character (by Biolog EcoPlateTM) in soils from sites heavily and lightly invaded by this exotic species. Also, soil from the lightly invaded site was treated with a water extract of E.adenophorum roots to examine the effect of the plant on soil properties. We grew three plant species, one native and two exotic, in pot experiment using soil from heavily invaded site to examine the effects of the soil on these plants growth. The soil analysis demonstrated that the pH, organic matter, total N, total P and total K in soils from the heavily invaded site were only slightly different from those of the lightly invaded site, but concentrations of NH4^ , NO3^- and available P and K in the heavily invaded site were greater than those in the lightly invaded site. The catabolic activity of soil bacterial community in the heavily invaded site was different from that in the lightly invaded site. The catabolic activity of bacterial community in soils treated by the water extract of E.adenophorum roots changed and became similar to that in soils from the heavily invaded site. The pot experiment showed that the exotic plants growth in heavily invaded soil were not different from in lightly invaded soil; however, the native plant biomass decreased dramatically when grown in soil from the heavily invaded site as compared to soil from the lightly invaded site; and the same phenomenon was found when any potential allelopathic effects by E. adenophorum were eliminated by added activated carbon to those soils. Difference in soil nutrient availability and allelopathy could not explain this phenomenon of the native plant in the soils from the heavily and lightly invaded sites. Changes observed in the soil bacterial community were obviously related to native plant growth in those tow soils. Those results suggest that changing soil microbial community may be an important part of E. adenophorum invasion process. Since the soil microbial community serves as bridge in connection of exotic and natural plants, the exotic plant could inhibit the natural plant growth and reproduction by changing the soil microbial community in invaded site.     

基于细菌觅食优化算法的图像聚类方法研究

利用细菌觅食优化算法研究图像聚类问题,采用群体智能模式实现问题解的搜索.首先提取图像特征以确定解的编码形式,初始化种群,在此基础上利用细菌觅食优化算法的细菌迁徙算子、繁殖算子和趋化算子实现群体内个体之间的相互合作和竞争,提高了算法的搜索能力,实验证明该算法具有较强的适应性和鲁棒性.     

细菌纤维素在造纸工业中的应用和展望

介绍了细菌纤维素的结构特点和功能特性及其在造纸工业中的应用现状．着重介绍了细菌纤维素在无纺布中的应用研究,研究表明细菌纤维素作为无纺布的胶粘剂,具有良好的粘结能力和广泛的适用范围,可有效改善织物的强度和性能．其生物降解性能有助于环境友好的无纺布产品的技术开发．     

Synthesis of a series of ethylene glycol modified water-soluble tetrameric TPE-amphiphiles with pyridinium polar heads: Towards applications as light-up bioprobes in protein and DNA assay,and wash-free imaging of bacteria

Available online Development of water soluble AIE-active “light-up” bioprobes for the detection of biomacromolecules has drawn huge research interests in recent past. In this study, a series of ethylene glycol modified water soluble tetrameric tetraphenylethylene amphiphiles with pyridinium polar heads (TPE-xEG-Py, x = 3, 4, 6 or 1a-c) have been synthesized by varying the ethylene glycol spacer. Their unique structure allows them to form vesicles and other nanoaggregates in aqueous solutions. These amphiphiles were successfully utilized for fluorimetric detection and quantitation of BSA and DNA based on the electrostatic interactions to trigger AIE-emission from the TPE moiety. The electrostatic interaction was also proved very effective in wash-free imaging of both Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria with up to 92 folds increase in fluorescence response within bacterial concentration 0–12 × 10⁸ CFU mL^?1. The strategy is advantageous due to cost-effective and easy synthesis, high water solubility, and fast response.     

Simultaneous isolation and label‐free identification of bacteria using contactless dielectrophoresis and Raman spectroscopy

The traditional bacterial identification method of growing colonies on agar plates can take several days to weeks to complete depending on the growth rate of the bacteria. Successfully decreasing this analysis time requires cell isolation followed by identification. One way to decrease analysis time is by combining dielectrophoresis (DEP), a common technique used for cell sorting and isolation, and Raman spectroscopy for cell identification. DEP‐Raman devices have been used for bacterial analysis, however, these devices have a number of drawbacks including sample heating, cell‐to‐electrode proximity that limits throughput and separation efficiency, electrode fouling, or inability to address sample debris. Presented here is a contactless DEP‐Raman device to simultaneously isolate and identify particles from a mixed sample while avoiding common drawbacks associated with other DEP designs. Using the device, a mixed sample of bacteria and 3 μm polystyrene spheres were isolated from each other and a Raman spectrum of the trapped bacteria was acquired, indicating the potential for cDEP‐Raman devices to decrease the analysis time of bacteria.     

基于全基因组序列的核桃细菌性黑斑病菌分泌蛋白的预测及特征分析

【目的】充分了解核桃黑斑病菌的侵染机制。【方法】以全基因组序列已经公布的7个核桃细菌性黑斑病菌菌株CFBP2528、CFBP7179、CFBP8253、DW3F3、J303、NCPPB1447、Xaj417等所具有的蛋白序列为预测数据,基于分泌蛋白所具有的主要特征,利用SignalP v4.1、ProtCompB v9.0、TMHMM v2.0、big-PI Fungal predictor、TargetP v1.1、LipoP v1.0等在线分析程序对分泌蛋白进行预测,同时分析其氨基酸组成及分布、信号肽长度、信号肽切割位点等特征。【结果】核桃细菌性黑斑病菌的分泌蛋白平均为74个,其氨基酸长度多集中于101～400氨基酸,所占比例为63.65%。信号肽氨基酸残基中以A最多,所占比例为22.04%; 其次是L,所占比例为19.27%。信号肽长度以19～29个氨基酸的最多,所占比例为79.62%,信号肽切割位点属于A-X-A类型。【结论】核桃细菌性黑斑病菌中分泌蛋白的有效预测,可为深入解析核桃细菌性黑斑病菌中分泌蛋白在侵染过程中所发挥的功能提供理论依据。     

Tobramycin and Nebramine as Pseudo‐oligosaccharide Scaffolds for the Development of Antimicrobial Cationic Amphiphiles

Antimicrobial cationic amphiphiles derived from aminoglycoside pseudo‐oligosaccharide antibiotics interfere with the structure and function of bacterial membranes and offer a promising direction for the development of novel antibiotics. Herein, we report the design and synthesis of cationic amphiphiles derived from the pseudo‐trisaccharide aminoglycoside tobramycin and its pseudo‐disaccharide segment nebramine. Antimicrobial activity, membrane selectivity, mode of action, and structure–activity relationships were studied. Several cationic amphiphiles showed marked antimicrobial activity, and one amphiphilic nebramine derivative proved effective against all of the tested strains of bacteria; furthermore, against several of the tested strains, this compound was well over an order of magnitude more potent than the parent antibiotic tobramycin, the membrane‐targeting antimicrobial peptide mixture gramicidin D, and the cationic lipopeptide polymyxin B, which are in clinical use.     

Revisiting the Origin of Bacterial Bioluminescence: QM/MM Study on Oxygenation Reaction of Reduced Flavin in Protein

Bacterial bioluminescence is initiated by the oxygenation reaction of reduced flavin mononucleotide in luciferase. This enzymatic oxygenation occurs in a wide range of biological processes including cellular redox metabolism, biocatalysis, biosynthesis and homeostasis. However, little is known about the mechanism of the enzymatic reaction between singlet reduced flavin and triplet oxygen. To explore the enigmatic oxygenation, for the first time, the reaction of reduced flavin anion with oxygen was studied in bacterial luciferase by a combined quantum mechanics and molecular mechanics method as well as molecular dynamics simulation. The calculated results demonstrate that the reaction proceeds via a proton-coupled electron transfer (PCET) pathway, and the essential αHis44 acts as a catalytic acid to provide the proton. The currently proposed PCET mechanism clearly describes the initial steps of bacterial bioluminescence, and could be suitable for the other flavin oxygenation reactions in enzymes.     

Chemical diversity and anti-acne inducing bacterial potentials of essential oils from selected Elsholtzia species

Essential oils from the aerial parts of four Elsholtzia species; Elsholtzia stachyodes, Elsholtzia communis, Elsholtzia griffithii and Elsholtzia beddomei were obtained by steam distillation and their chemical components were analysed by gas chromatography-mass spectrometry (GC-MS). Principle Component Analysis was used to identify the chemical variations in the essential oils from these plants, which could be categorised into two groups according to their main chemical components which are acylfuran derivatives and oxygenated monoterpenes. Additionally, the anti-acne inducing bacterial activity against Staphylococcus aureus and Staphylococcus epidermidis were evaluated. The oil from E. stachyodes was the most efficacious against the growth of S. aureus and S. epidermidis having MIC values of 0.78 and 1.56 μL/mL, respectively, and exhibited five times more effective than erythromycin (standard antibiotic).