湖南鱼类新记录4种

2004年8月～2005年7月,在湖南安化进行鱼类资源调查期间,发现湖南鱼类新记录4种：漓江副沙鳅、盎堂拟鲿、越南鲇和司氏（鱼央）.     

Monitoring of gene knockouts: genome-wide profiling of conditionally essential genes

We have developed a new microarray-based genetic technique, named MGK (Monitoring of Gene Knockouts), for genome-wide identification of conditionally essential genes. MGK identified bacterial genes that are critical for fitness in the absence of aromatic amino acids, and was further applied to identify genes whose inactivation causes bacterial cell death upon exposure to the bacteriostatic antibiotic chloramphenicol. Our findings suggest that MGK can serve as a robust tool in functional genomics studies.     

A comprehensive analysis of root morphological changes and nitrogen allocation in maize in response to low nitrogen stress

The plasticity of root architecture is crucial for plants to acclimate to unfavourable environments including low nitrogen (LN) stress. How maize roots coordinate the growth of axile roots and lateral roots (LRs), as well as longitudinal and radial cell behaviours in response to LN stress, remains unclear. Maize plants were cultivated hydroponically under control (4 mm nitrate) and LN (40 μm ) conditions. Temporal and spatial samples were taken to analyse changes in the morphology, anatomical structure and carbon/nitrogen (C/N) ratio in the axile root and LRs. LN stress increased axile root elongation, reduced the number of crown roots and decreased LR density and length. LN stress extended cell elongation zones and increased the mature cell length in the roots. LN stress reduced the cell diameter and total area of vessels and increased the amount of aerenchyma, but the number of cell layers in the crown root cortex was unchanged. The C/N ratio was higher in the axile roots than in the LRs. Maize roots acclimate to LN stress by optimizing the anatomical structure and N allocation. As a result, axile root elongation is favoured to efficiently find available N in the soil.     

Enterococcus faecalis pCF10‐encoded surface proteins PrgA,PrgB (aggregation substance) and PrgC contribute to plasmid transfer,biofilm formation and virulence

Enterococcus faecalis pCF10 transfers at high frequencies upon pheromone induction of the prgQ transfer operon. This operon codes for three cell wall‐anchored proteins – PrgA, PrgB (aggregation substance) and PrgC – and a type IV secretion system through which the plasmid is delivered to recipient cells. Here, we defined the contributions of the Prg surface proteins to plasmid transfer, biofilm formation and virulence using the Caenorhabditis elegans infection model. We report that a combination of PrgB and extracellular DNA (eDNA), but not PrgA or PrgC, was required for extensive cellular aggregation and pCF10 transfer at wild‐type frequencies. In addition to PrgB and eDNA, production of PrgA was necessary for extensive binding of enterococci to abiotic surfaces and development of robust biofilms. However, although PrgB is a known virulence factor in mammalian infection models, we determined that PrgA and PrgC, but not PrgB, were required for efficient killing in the worm infection model. We propose that the pheromone‐responsive, conjugative plasmids of E. faecalis have retained Prg‐like surface functions over evolutionary time for attachment, colonization and robust biofilm development. In natural settings, these biofilms are polymicrobial in composition and constitute optimal environments for signal exchange, mating pair formation and widespread lateral gene transfer.     

大鼠胰岛分离、培养条件的优化及miR-126表达的检测方法比较

目的:优化SD大鼠胰岛细胞的分离、纯化和培养方法与条件,为研究miR-126在Ⅱ型糖尿病中的作用机制提供活性与功能良好的胰岛细胞及miR-126表达的检测方法。方法:水合氯醛腹腔注射麻醉SD大鼠,采用8 mL胶原酶Ⅴ(含DNaseⅠ100 U)逆行注射、原位消化后Hitopaque-1077梯度离心分离纯化SD大鼠胰岛细胞,从培养后的胰岛细胞中提取总RNA,分别用加尾法和茎环法进行miR-126的反转录,实时定量PCR(qPCR)检测miR-126的表达量。结果:用该方法可从每只SD大鼠中分离、纯化得到胰岛细胞372±45个,胰岛细胞纯度90%,胰岛细胞存活率95%;用加尾法和茎环法qPCR检测miR-126的Cp值分别为34.56±2.56和32.47±2.01。结论:胶原酶Ⅴ(含DNaseⅠ100 U)逆行注射、原位消化可有效避免因消化时胶状物质的产生而导致的胰岛细胞分离失败,Hitopque-1077梯度离心分离方法具有操作简单、便捷、成功率高等特点,可得到活性与功能较好的胰岛细胞;与加尾法相比,茎环法能够更灵敏地检测胰岛细胞miR-126的表达量。