Changes in microbial community structure and function within particle size fractions of a paddy soil under different long-term fertilization treatments from the Tai Lake region, China

Greenhouse gas (GHG) production and emission from paddy soils impacts global climate change. Soil particle size fractions (PSFs) of different sizes act as soil microhabitats for different kinds of microbial biota with varying conditions of redox reactions and soil organic matter (SOC) substrates. It is crucial to understand the distribution of soil microbial community structure within PSFs and linkage to the GHG production from paddy soils of China. The change of bacterial and methangenic archaeal community and activity relating to CH₄ and CO₂ production with PSFs under different fertilizer applications was studied in this paper. The fertilization trial was initiated in a paddy soil from the Tai Lake region, Jiangsu, China with four treatments of non-fertilized (NF), fertilized with inorganic fertilizers only (CF), inorganic with pig manure (CFM) and inorganic with straw return (CFS), respectively since 1987, and the PSFs (<2 μm, 2–20 μm, 20–200 μm, and 200–2000 μm) were separated by a low energy sonication dispersion procedure from undisturbed samples. Analysis of bacterial community within different size particles was conducted by PCR-DGGE. The results indicated significant variation of bacterial community structure within different PSFs. The methane was predominantly produced in the coarser fractions, while more species and higher diversity of bacteria survived in the size of <2 μm fractions, in which the bacterial community structure was more significantly affected by fertilizer application practices than in the other coarser fractions. Higher bacterial species richness and more diversities in the smallest size fractions was due to the vicinity between microbes, access to carbon resource outside the microaggregates, and smaller pore size as protective agent suitable habitats for microbes rather than high SOC. Whereas, higher CO₂, CH₄ production and methanogenic archaeal community in coarser fractions may be contributed to storage of labile organic carbon in these fractions. It indicated that availability of SOC in PSFs is mainly factor affected survival of methanogenic archaeal community structure, whereas, bacterium community habitation more affected by physical protection of their location in PSFs. Their activity greatly depended on liability of SOC access to PSFs. Fertilizer application caused more change of bacteria community in clay fraction and greatly increased bacterium and methanogen activity in coarser fractions but only a slight effect on methanogenic archaeal community in the particle size fractions.     

细菌性鱼病的免疫研究现状

概述了细菌性鱼病的免疫研究现状,主要介绍鱼用细菌性疫苗的研制、接种途径及免疫效果的评价,指出了鱼类免疫研究的发展前景及其存在的问题     

纳米细菌纤维素膜的表征与生物相容性研究

利用木醋杆菌静态培养法制备的由纳米纤维组成的细菌纤维素膜具有超细的三维网络结构和适当的孔隙率. 利用光镜、扫描电镜和原子力显微镜对其进行结构表征发现, 细菌纤维素膜具有极为精细的纳米网络结构, 冻干膜的孔径约为0.6~2.8 μm; 纤维素带宽度约为50~80 nm. 采用湿重与浮重结合法测定烘干膜和冻干膜的孔隙率分别约为70%和90%. 由于细菌纤维素含有大量的羟基, 故烘干膜表现出极好的透湿性. 将细菌纤维素膜分别与成纤维细胞和软骨细胞进行复合培养, 并将成纤维细胞和细菌纤维素膜的复合物进行裸鼠皮下移植实验. 结果显示, 移植的复合物很好地融入了裸鼠正常皮肤, 成纤维细胞和软骨细胞在细菌纤维素表面形成连续的细胞层, 绿色荧光蛋白表达正常. 以上结果表明, 细菌纤维素膜非常适合细胞贴附和增殖, 表现出较好的生物相容性, 有望成为新型组织工程支架材料.     

Screening of fluorinated materials degrading microbes

Isolation of bacterial strains capable of degrading fluorinated materials was described. 8 strains of Actinobacteria exhibited degradability of ethyl difluoroacetate (DFAc) was accumulated by bacteria, giving difluoroacetic acid and then fluoride ion. Further, 13 strains of Actinobacteria exhibited degradability of fluorobenzene and/or benzotrifluoride. In batch culture, growth of strains on fluorinated materials led to the release of fluoride ion.     

Efficient removal of DNA from proteomic samples prior to two-dimensional map analysis

Several methods have been described in the literature for removal of DNA from protein samples prior to proteome analysis. They in general involve protein precipitation techniques. In other protocols, DNAse treatment is suggested prior to precipitation of proteins in excess acetone. All these methods have been evaluated and found to perform poorly in DNA removal, as illustrated by two-dimensional (2D) maps where horizontal and vertical sample streaking are still substantial. Such removal is in general necessary in tissue lysates and especially when analysing sub-cellular organelles, such as nuclei, where the high DNA levels strongly interfere with proteome analysis. Another method is proposed here for efficient DNA removal: two-phase extraction of DNA in chloroform/phenol/isoamyl alcohol, a procedure commonly used to rid DNA samples of protein contaminants, but rarely applied to protein preparation. This extraction is not very efficient if performed at slightly acidic to neutral pH values, but it performs extremely well at pH values of 9.5 or higher. The 2D maps thus obtained of Escherichia coli lysates as well as extracts from purified nuclei of eukaryotic cells are not only devoid of any vertical or horizontal streaking, but exhibit many more spots, especially in the alkaline region of the 2D gels, suggesting that these basic proteins were in general lost to proteome analysis due to co-precipitation in tenacious protein–DNA complexes. It is hypothesized that the alkaline pH values adopted in the two-phase extraction help to fully disrupt any residual DNA–protein complexes, due to strong Coulombic repulsion.     

Rapid detection of Staphylococcus aureus by a combination of monoclonal antibody-coated latex and capillary electrophoresis

The rapid detection of pathogenic bacteria is extremely important in biotechnology and clinical diagnosis. CE has been utilized in the field of bacterial analysis for many years, but to some extent, simultaneous separation and identification of certain microbes from complex samples by CE coupled with UV detector is still a challenge. In this paper, we propose a new strategy for rapid separation and identification of Staphylococcus aureus (S. aureus) in bacterial mixtures by means of specific mAb-coated latex coupled with CZE. An appropriate set of conditions that selectively isolated S. aureus from the microorganisms Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae were established. S. aureus could be differentiated from the others by unique peaks in the electropherograms. The validity was also confirmed by LIF with antibodies specific to both the latex and the microbial cells. The LOD is as low as 9.0 x 10(5) colony forming unit/mL. We have also utilized this technology to identify S. aureus in a stool sample coming from a healthy volunteer spiked successfully with S. aureus. This CZE-UV technique can be applied to rapid diagnosis of enteritis caused by S. aureus or other bacterial control-related fields needing rapid identification of target pathogens from microbial mixtures. In theory, this method is suitable for the detection of any bacterium as long as corresponding bacterium-specific antibody-coated latex is available.     

Surface modification of polyester to produce a bacterial cellulose-based vascular prosthetic device

The surface of medical grade polyesters was modified to impart hydrophilic character for attachment to bacterial synthesized cellulose to produce a vascular prosthetic device. The polyesters were treated with UV/ozone, air plasma, and nitrogen plasma for various lengths of time. The unmodified and modified surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and advancing contact angle measurements. The surfaces were then coated with bacterial produced cellulose to study adhesion properties through tensile testing (peel testing). UV/ozone and plasma treatment XPS results indicated an increase in the oxygen concentration in the form of CO(H) on the treated polyester surfaces. The treatment time to reach steady state in the case of air and nitrogen plasmas took the order of seconds, while 7 min and longer were required for UV/ozone treatment. Peel strength tests to measure adhesion of modified polyester to cellulose reached their maximum values when the CO(H) concentrations were at the highest level. It was also at this level that the contact angle measurements showed no further decrease.     

纳米银在细菌纤维素凝胶膜中的原位合成及性能表征

在细菌纤维素纳米纤维网络结构中采用吐伦试剂与含醛基化合物原位反应生成纳米银颗粒, 制备了纳米银/细菌纤维素(n-Ag/BC)复合凝胶膜, 研究了不同反应条件对复合材料的银含量、 化学结构和晶体结构的影响以及n-Ag/BC的微观结构和纳米银在纤维素网络中的存在形态; 探讨了纳米银颗粒在纤维素网络中的形成机理; 采用伤口常见细菌之一金黄色葡萄球菌测试了n-Ag/BC的抑菌性能; 将n-Ag/BC与胎鼠表皮细胞共培养考察了材料的生物相容性. 研究结果表明, 在细菌纤维素纳米网络结构中可生成直径约为几十纳米的单质纳米银粒子; n-Ag/BC的银含量随着吐伦试剂浓度的增加而增加, 同时银含量还取决于含醛基化合物的用量; 原位反应生成纳米银粒子后细菌纤维素的晶型和结晶度没有发生变化; 纳米银颗粒在细菌纤维素纳米网络结构的交叉处生成, 复合材料n-Ag/BC对金黄色葡萄球菌的抑菌率达到99%以上, 不影响细胞的增殖和分化过程, 具有良好的生物相容性, 是一种有广阔应用前景的创伤修复抗感染材料.     

Optimization of Preparation Process for Allylamine-bacterial Cellulose via Graft Copolymerization by Response Surface Methodology

In order to improve the efficiency of new adsorbent, grafting-allylamine bacterial cellulose（al-BC）, response surface methodology（RSM） was used for the optimization of preparation process. Three factors affecting the yield of grafting reaction are the amount of allylamine, the concentration of ceric ammonium nitrate（CAN） and the concentration of nitric acid. Based on the regression coefficient analysis in the Box-Behnken design, a relationship between the preparation variable and grafting yield was obtained. Square error analysis on main factors, and multi-variable interactions were employed for studying grafting yield. The results show that at the conditions of CAN of 23.00 mmol/L CAN, 0.17 mol/L nitric acid, adding an amount of grafting-allylamine bacterial cellulose of 26.49 mL/L made grafting rate reach maximum of 24.25% at 40℃ after the reaction for 4 h. The experimental results are in good agreement with the calculation values via proposed regression equation, indicating that the equation could be used to nredict and optimizate the preparation of grafting al-BC.