Comparative analysis of the structure of incompatibility plasmids N, P and W

Evolutionary relationships of the IncN plasmid R15 and other broad host range plasmids (IncN plasmids N3 and R46, IncP plasmids RP4 and R906, IncW plasmids Sa and R388) were studied by Southern blot hybridization technique. The IncN plasmids were shown to harbour homologous determinants for replication and conjugation. No homology was found between the rep and tra genes in R15 and in the IncW and IncP plasmids, respectively. The second rep region of the N3 plasmid is distinctive from the corresponding determinants in the IncN plasmids. Homology was demonstrated for the plasmid genes that mediate restriction and modification in R15 and N3, mercury resistance in R15 and R906, sulfanilamide resistance in R15, N3, R46, Sa, R388, and R906, streptomycin resistance in R15, R46 and Sa. The latter genes are different from the R906 SmR gene. In addition to the three known mobile elements in the plasmid R15, the fourth one (IS46) that is a part of the transposon Tn2353 was identified in this study. Besides, the third copy of this insertion sequence was found in the N3 plasmid.     

宁德水产养殖区水质状况及驱动力分析

水产养殖对海岸带生态系统的水环境有显著影响,研究水产养殖地区的水质动态及其驱动力对海洋牧场建设和海岸带生态系统管理有着重要意义。以宁德为研究区域,基于2017年夏季和冬季水质监测和遥感影像等数据,通过地理信息系统技术和统计分析软件,分析了水产养殖区域的水质现状、水质变化和驱动力。结果表明,该海域水质处于重污染状态,富营养化水平较高。除了悬浮物和总磷之外,其他水质指标都呈现出显著的季节性差异,不同季节影响水质的因素也不相同。水质的季节性变化是初始水质状况、养殖活动和自然因素共同作用的结果。基于研究结果,笔者建议结合高分遥感技术对养殖区水面覆盖和利用进行监测,对养殖类型和行为(如饵料类型和投放方式)进行调控,开展水质长期监测和风险应急管理,保障海洋牧场社会经济效益的同时降低生态环境影响、防控生态和人体健康风险。     

Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High‐Performance All‐Vanadium Redox Flow Battery Membrane

A novel low‐cost nanoporous polytetrafluoroethylene (PTFE)/silica composite separator has been prepared and evaluated for its use in an all‐vanadium redox flow battery (VRB). The separator consists of silica particles enmeshed in a PTFE fibril matrix. It possesses unique nanoporous structures with an average pore size of 38 nm and a porosity of 48%. These pores function as the ion transport channels during redox flow battery operation. This separator provides excellent electrochemical performance in the mixed‐acid VRB system. The VRB using this separator delivers impressive energy efficiency, rate capability, and temperature tolerance. In additon, the flow cell using the novel separator also demonstrates an exceptional capacity retention capability over extended cycling, thus offering excellent stability for long‐term operation. The characteristics of low cost, excellent electrochemical performance and proven chemical stability afford the PTFE/silica nanoporous separator great potential as a substitute for the Nafion membrane used in VRB applications.     

Phytolith‐rich biochar: A potential Si fertilizer in desilicated soils

Silicon (Si) is beneficial to plants since it increases photosynthetic efficiency, and alleviates biotic and abiotic stresses. In the most highly weathered and desilicated soils, plant phytoliths make up the reservoir of bioavailable Si. The regular removal of crop residues, however, substantially decreases this pool. Si supply may therefore be required to sustain continuous cropping. Available Si fertilizers are costly and usually poor in soluble Si. Biochar produced from the pyrolysis of phytolith‐rich biomass is thus a promising alternative Si source for plants. Taking into account the challenges of increasing food demand and environmental concerns, we evaluate the global potential of biochar produced from major crop residues and manures in terms of phytogenic Si (PhSi) supply. Crop residues contribute to 80% of the global production of biomass dry matter (8,201 Tg/year) of which 3,137 Tg/year are potentially available after pyrolysis, giving a potential application rate of 1.7 T ha^?1 year^?1 for highly weathered soils in the tropics. The potential PhSi supply from crop biochar amounts to 102 Tg Si/year. On its own, rice straws produce 57.7 Tg PhSi/year, accounting for 56.6% of the potential annual PhSi production. The Si release from crop biochar depends on inter altere feedstock type, pyrolysis temperature, soil pH, and buffer capacity. Furthermore, the amplitude of plant Si uptake and mineralomass depends on plant species, soil properties, and processes. These factors interact and can exert a decisive influence on the effectiveness of phytolithic biochar in releasing Si into highly weathered soils. We conclude that the use of phytolithic biochar as a Si fertilizer offers undeniable potential to mitigate desilication and to enhance Si ecological services due to soil weathering and biomass removal. This potential must be explored, as well as the conditions for using biochar in the field.     

Use of polyethyleneimine polymer in cell culture as attachment factor and lipofection enhancer

Background  

Several cell lines and primary cultures benefit from the use of positively charged extracellular matrix proteins or polymers that enhance their ability to attach to culture plates. Polyethyleneimine is a positively charged polymer that has gained recent attention as a transfection reagent. A less known use of this cationic polymer as an attachment factor was explored with several cell lines.     

The cotransduction of pET system plasmids by mutants of T4 and RB43 bacteriophages

The study of the cotransduction of the plasmid pairs pET-3a-pLysE and pET-3a-pLysS by the mutant phage T4alc7 showed that the antibiotic resistance markers of the plasmids were cotransduced with a high frequency. The analysis of the plasmid DNA of cotransductants and cotransformants showed that the mutant phage T4alc7 can be used for obtaining the monomeric and oligomeric forms of plasmids and for the cotransduction of two-plasmid overproduction systems into E. coli strains. The plaque mutants RB43-03 and RB43-13 derived from bacteriophage RB43 were found to be able to cotransduce the antibiotic resistance markers of pET-3a and pLysE plasmids.