利用CRISPR/Cas9技术构建基因编辑大鼠模型

RNA介导的CRISPR/Cas9基因编辑系统由单链引导RNA(sgRNA)与核酸酶Cas9构成。在细胞内,sgRNA能够按照碱基互补配对的原则引导Cas9与靶点结合,由Cas9切割目标DNA,造成双链DNA断裂(double stranded break,DSB)。在随后的DNA修复过程中,细胞主要进行非同源末端连接(non-homologous end joining,NHEJ)或在有修复模板存在的情况下进行重组修复(homology directed repair,HDR)。如果将CRISPR/Cas9系统以及修复模板通过显微注射的方式导入大鼠的胚胎内,就能借助细胞的修复机制实现大鼠胚胎的基因编辑,由此构建各种基因修饰大鼠模型。本文详细介绍了利用CRISPR/Cas9基因编辑技术构建大鼠模型的具体操作步骤,以期为相关领域的科研人员提供一种大鼠基因修饰模型的构建方法。

Strategic Thinking and Measures for Plant Quarantine and Food Safety

This paper describes the importance of plant quarantine to the food safety in China through cases where plant quarantine helps to effectively intercept harmful organisms for food safety and promote export and import trading.It also presents the existing problems in plant quarantine work and appropriate measures.

Pioneer to exploration and construction of Jilin Province s higher medical laboratory education and talent training system

Professor Tingbin Yang(杨廷彬)has dedicated his whole life to education science and microbiology research.He is not only an excellent microbiologist but also an outstanding educator.He has finished many professional books and got several honors for his job.Prof.Yang has contributed a lot for the development of medical laboratory education in China and clinical medicine.

Biodegradation of 2-methylquinoline by Enterobacter aerogenes TJ-D isolated from activated sludge

Bacterial strain Enterobacter aerogenes TJ-D capable of utilizing 2-methylquinoline as the sole carbon and energy source was isolated from acclimated activated sludge under denitrifying conditions. The ability to degrade 2-methylquinoline by E. aerogenes TJ-D was investigated under denitrifying conditions. Under optimal conditions of temperature （35°C） and initial pH 7, 2-methylquinoline of 100 mg/L was degraded within 176 hr. The degradation of 2-methylquinoline by E. aerogenes TJ-D could be well described by the Haldane model （R 2 〉 0.91）. During the degradation period of 2-methylquinoline （initial concentration 100 mg/L）, nitrate was almost completely consumed （the removal efficiency was 98.5%）, while nitrite remained at low concentration （〈 0.62 mg/L） during the whole denitrification period. 1,2,3,4-Tetrahydro-2-methylquinoline, 4-ethyl-benzenamine, N-butyl-benzenamine, N-ethyl-benzenamine and 2,6-diethyl-benzenamine were metabolites produced during the degradation. The degradation pathway of 2-methylquinoline by E. aerogenes TJ-D was proposed. 2-Methylquinoline is initially hydroxylated at C-4 to form 2-methyl-4-hydroxy-quinoline, and then forms 2-methyl-4-quinolinol as a result of tautomerism. Hydrogenation of the heterocyclic ring at positions 2 and 3 produces 2,3-dihydro-2-methyl-4-quinolinol. The carbon-carbon bond at position 2 and 3 in the heterocyclic ring may cleave and form 2-ethyl-N-ethyl-benzenamine. Tautomerism may result in the formation of 2,6-diethyl-benzenamine and N-butyl-benzenamine. 4- Ethyl-benzenamine and N-ethyl-benzenamine were produced as a result of losing one ethyl group from the above molecules.

典型有机固废厌氧消化微生物研究现状与发展方向

经过人工富集和驯化的兼性和严格厌氧微生物是厌氧消化工艺的核心。不同厌氧消化体系中存在的问题大多可以通过改变微生物群落的代谢活性来得到有效改善。得益于微生物组学检测技术的快速发展,对厌氧消化系统中微生物多样性的认识获得了极大的拓展,同时在微生物类群间、微生物与环境的互作关系研究方面也取得了一系列新的进展。然而,有机固废厌氧消化系统中,各种微生物以及微生物和物质的相互作用构成了更为复杂的代谢网络,所以目前对这些互作关系的解析尚不完善。本文重点关注了厌氧消化过程中的典型菌群互作关系,阐述了典型有机固废厌氧消化系统中存在的问题及微生物在其中发挥的作用,最后,立足于现有组学技术推动的微生物组研究进展,对未来有机固废厌氧消化系统微生物组的研究提出展望。

Distribution and seasonal variation of estrogenic endocrine disrupting compounds,N-nitrosodimethylamine, and N-nitrosodimethylamine formation potential in the Huangpu River, China

Detection of estrogenic endocrine disrupting compounds （EDCs） and N-nitrosodimethylamine （NDMA） in drinking water has led to rising concerns. There are, however, a paucity of studies on the distribution and seasonal variation of NDMA and NDMA formation potential （NDMA-FP） in natural waters, especially in China. For EDCs, limited studies have investigated the distribution and seasonal variation of estrone （El）, 1713-estradiol （E2）, estriol （E3）, 17a-ethinylestradiol （EE2）, technical-nonylphenols （t-NP）, and bisphenol A （BPA） in Shanghai. In this study, water samples were collected from 11 sampling sites along the Huangpu River in 2012. The distribution and seasonal variation of EDCs, NDMA, and NDMA-FP were investigated. The results showed that all of the 11 sampling sites were contaminated by the target compounds. Compared with E2 and EE2, higher E1 and E3 concentrations were usually detected in the Huangpu River. The values of 17β- estradiol equivalents （EEQ） suggest a high possibility of endocrine effects on exposed organisms in the Huangpu River. NDMA-FP and t-NP were the dominant contaminants among the eight target compounds. The detection rates of the target compounds and their concentrations were both higher in dry seasons than in wet seasons. Higher concentrations of target compounds were observed in urban sampling sites near drainage outlets, and also in suburban sampling sites where intensive livestock farming and farmlands were located.

Waste activated sludge hydrolysis and acidification： A comparison between sodium hydroxide and steel slag addition

Alkaline treatment with steel slag and NaOH addition were investigated under different pH conditions for the fermentation of waste activated sludge. Better performance was achieved in steel slag addition scenarios for both sludge hydrolysis and acidification. More solubilization of organic matters and much production of higher VFA （volatile fatty acid） in a shorter time can be achieved at pH 10 when adjusted by steel slag. Higher enzyme activities were also observed in steel slag addition scenarios under the same pH conditions. Phosphorus concentration in the supematant increased with fermentation time and pH in NaOH addition scenarios, while in contrast most phosphorus was released and captured by steel slag simultaneously in steel slag addition scenarios. These results suggest that steel slag can be used as a substitute for NaOH in sludge alkaline treatment.

Elucidating the removal mechanism of N,N-dimethyldithiocarbamate in an anaerobic-anoxic-oxic activated sludge system

N,N-Dimethyldithiocarbamate （DMDTC） is a typical precursor of N-nitrosodimethylamine （NDMA）. Based on separate hydrolysis, sorption and biodegradation studies of DMDTC, a laboratory-scale anaerobic-anoxic-oxic （AAO） system was established to investigate the removal mechanism of DMDTC in this nutrient removal biological treatment system. DMDTC hydrolyzed easily in water solution under either acidic conditions or strong alkaline conditions, and dimethylamine （DMA） was the main hydrolysate. Under anaerobic, anoxic or oxic conditions, DMDTC was biodegraded and completely mineralized. Furthermore, DMA was the main intermediate in DMDTC biodegradation. In the AAO system, the optimal conditions for both nutrient and DMDTC removal were hydraulic retention time 8 hr, sludge retention time 20 day, mixed-liquor return ratio 3：1 and sludge return ratio 1：1. Under these conditions, the removal efficiency of DMDTC reached 99.5%; the removal efficiencies of chemical organic demand, ammonium nitrogen, total nitrogen and total phosphorus were 90%, 98%, 81% and 93%, respectively. Biodegradation is the dominant mechanism for DMDTC removal in the AAO system, which was elucidated as consisting of two steps： first, DMDTC is transformed to DMA in the anaerobic and anoxic units, and then DMA is mineralized to CO2 and NH3 in the anoxic and oxic units. The mineralization of DMDTC in the biological treatment system can effectively avoid the formation of NDMA during subsequent disinfection processes.

Characterization of N-nitrosodimethylamine formation from the ozonation of ranitidine

N-nitrosodimethylamine（NDMA） is an emerging disinfection by-product which is formed during water disinfection in the presence of amine-based precursors. Ranitidine, as one kind of amine-based pharmaceuticals, has been identified as NDMA precursor with high NDMA molar conversion during chloramination. This study focused on the characterization of NDMA formation during ozonation of ranitidine. Influences of operational variables（ozone dose, pH value） and water matrix on NDMA generation as well as ranitidine degradation were evaluated. The results indicate high reactivity of ranitidine with ozone.Dimethylamine（DMA） and NDMA were generated due to ranitidine oxidation. High pH value caused more NDMA accumulation. NDMA formation was inhibited under acid conditions（pH ≤ 5） mainly due to the protonation of amines. Water matrix such as HCO-3and humic acid impacted NDMA generation due to UOH scavenging. Compared with UOH,ozone molecules dominated the productions of DMA and NDMA. However, UOH was a critical factor in NDMA degradation. Transformation products of ranitidine during ozonation were identified using gas chromatography–mass spectrometry. Among these products, just DMA and N,N-dimethylformamide could contribute to NDMA formation due to the DMA group in the molecular structures. The NDMA formation pathway from ranitidine ozonation was also proposed.