高通量扩增子测序分析生防细菌对丹参根际和根表土壤真菌群落多样性的影响

利用高量测序方法探究生防细菌对丹参植株根际和根表土壤真菌群落多样性的影响。

向丹参植株根部施入生防细菌DS-R5,培养45 d后采集根际和根表土壤样品提取总DNA,扩增样品基因组DNA的V4―V5区后进行双端测序,利用生物信息学解析生防细菌对丹参植株根际和根表土壤真菌群落多样性的影响。

菌株DS-R5处理后增加了根际和根表土壤真菌群落的多样性和丰度;根际土壤共有物种种类大于根表土壤,说明菌株DS-R5处理后根际土壤处理与对照物种种类更接近,而对根表土壤中的微生物物种影响较大。真菌群落结构组成分析结果表明,不同土壤样品在门水平上共有优势真菌主要有子囊菌门、接合菌门、担子菌门和未分类;相比根表土壤对照样品,根表土壤处理样品中子囊菌门丰度下降了13.0%,接合菌门丰度升高了69.2%;根际土壤处理样品相比根际土壤对照样品,子囊菌门和接合菌门丰度分别升高了5.9%和8.9%,但二者差异无统计学意义。在属水平上,根表土壤样品经菌株DS-R5处理后提高了有益菌属的丰度,同时降低了有害菌属的丰度。

丹参植株施入生防细菌后,改变了根际土壤和根表土壤中微生物群落结构和多样性,本研究结果可以为利用生防细菌防控丹参根腐病提供理论参考。

     

Effects of Water Stress and Abscisic Acid on Transpiration Regulation in Wheat

The transpiration response to recurrent light periods was studied'n water-stressed wheat seedlings. Seedlings were stressed by three methods: addition of mannitol to the root medium, root cooling and drving of the roots in air. All three methods induced almost equal effects on transpiration regulation during alternating dark and light intervals. Exogenous abscisic acid supplied to the shoots of excised plants had qualitatively the same effect as water stress. Water stress and ABA increased the time lapse between light-on and the onset of transpiration increase and lowered the amplitude of transpiration increase in light. Weak light introduced before strong light shortened the delay times.     

Sulfate-mediated affinity chromatography on NADP+-Sepharose of glutamate dehydrogenase from halophilic bacteria and of glucose-6-phosphate dehydrogenase from Escherichia coli.

An improved synthesis of the 8-(6-aminohexyl)amino derivative of NADP+ is described for use in affinity chromatography. The binding of glutamate dehydrogenase isolated from halobacterium of the Dead Sea on a column of Sepharose linked to this NADP+ derivative could be drastically enhanced by addition of sulfate (1M) and provided a tool for partially purifying the enzyme from a crude extract. A similar finding is reported for glucose-6-phosphate dehydrogenase in crude extracts of Escherichia coli. The effects are shown to be biospecific, suggesting that the strength of the interaction between protein and immobilized coenzymes is a function of the sulfate concentration.     

A Systematic Review on the Diagnosis of Pediatric Bacterial Pneumonia: When Gold Is Bronze

Background

In developing countries, pneumonia is one of the leading causes of death in children under five years of age and hence timely and accurate diagnosis is critical. In North America, pneumonia is also a common source of childhood morbidity and occasionally mortality. Clinicians traditionally have used the chest radiograph as the gold standard in the diagnosis of pneumonia, but they are becoming increasingly aware that it is not ideal. Numerous studies have shown that chest radiography findings lack precision in defining the etiology of childhood pneumonia. There is no single test that reliably distinguishes bacterial from non-bacterial causes. These factors have resulted in clinicians historically using a combination of physical signs and chest radiographs as a ‘gold standard’, though this combination of tests has been shown to be imperfect for diagnosis and assigning treatment. The objectives of this systematic review are to: 1) identify and categorize studies that have used single or multiple tests as a gold standard for assessing accuracy of other tests, and 2) given the ‘gold standard’ used, determine the accuracy of these other tests for diagnosing childhood bacterial pneumonia.

Methods and Findings

Search strategies were developed using a combination of subject headings and keywords adapted for 18 electronic bibliographic databases from inception to May 2008. Published studies were included if they: 1) included children one month to 18 years of age, 2) provided sufficient data regarding diagnostic accuracy to construct a 2×2 table, and 3) assessed the accuracy of one or more index tests as compared with other test(s) used as a ‘gold standard’. The literature search revealed 5,989 references of which 256 were screened for inclusion, resulting in 25 studies that satisfied all inclusion criteria. The studies examined a range of bacterium types and assessed the accuracy of several combinations of diagnostic tests. Eleven different gold standards were studied in the 25 included studies. Criterion validity was calculated for fourteen different index tests using eleven different gold standards. The most common gold standard utilized was blood culture tests used in six studies. Fourteen different tests were measured as index tests. PCT was the most common measured in five studies each with a different gold standard.

Conclusions

We have found that studies assessing the diagnostic accuracy of clinical, radiological, and laboratory tests for bacterial childhood pneumonia have used a heterogeneous group of gold standards, and found, at least in part because of this, that index tests have widely different accuracies. These findings highlight the need for identifying a widely accepted gold standard for diagnosis of bacterial pneumonia in children.     

Heavy drinking relates to positive valence ratings of alcohol cues

A positive family history of alcohol use disorders (FH) is a robust predictor of personal alcohol abuse and dependence. Exposure to problem-drinking models is one mechanism through which family history influences alcohol-related cognitions and drinking patterns. Similarly, exposure to alcohol advertisements is associated with alcohol involvement and the relationship between affective response to alcohol cues and drinking behavior has not been well established. In addition, the collective contribution that FH, exposure to different types of problem-drinking models (e.g. parents, peers) and personal alcohol use have on appraisal of alcohol-related stimuli has not been evaluated with a large sample. We investigated the independent effects of FH, exposure to problem-drinking models and personal alcohol use on valence ratings of alcohol pictures in a college sample. College students (n = 227) completed measures of personal drinking and substance use, exposure to problem-drinking models, FH and ratings on affective valence of 60 alcohol pictures. Greater exposure to non-familial problem-drinkers predicted greater drinking among college students (beta = 0.17, P < 0.01). However, personal drinking was the only predictor of valence ratings of alcohol pictures (beta = -0.53, P < 0.001). Personal drinking level predicted valence ratings of alcohol cues over and above FH, exposure to problem-drinking models and demographic characteristics. This suggests that positive affective responses to alcohol pictures are more a function of personal experience (i.e. repeated heavy alcohol use) than vicarious learning.     

Biosynthesis of chlorophyll P-680 of photosystem II in greening leaves of plants adapted to heat shock

In etiolated pea and maize leaves illuminated after incubation at 38 degreesC, a new dark reaction was shown manifested in the bathochromic shift of spectral bands and accompanied by esterification of the product of protochlorophyllide photochemical reduction--Chld 684/676: Chld 684/676 --> Chl 688/680. After completion of the reaction a rapid (20-30 sec) quenching of the fluorescence of the reaction product (Chl 688/680) was observed. The reaction Chld 684/676 --> Chl 688/680 is inhibited under anaerobic conditions and in the presence of cyanide; the reaction accompanied by Chl 688/680 fluorescence quenching is not observed in pea mutants with impaired function of photosystem II reaction centers. The spectral properties of the formed Chl form with the absorption maximum at 680 nm, fluorescence quenching, and simultaneous synthesis of pheophytin suggest that the reaction is connected with the chlorophyll of photosystem II reaction center--P-680.     

甜仁山杏优株幼果抗寒性研究

以2个优选的甜仁山杏的幼果为试材．以生产中主栽大扁杏品种“优一”和野生山杏（山苦1、山苦2）为对照,通过冷冻处理,以胚褐变率、电导率和MDA值为指标,研究了甜仁山杏优株的抗寒性。结果表明。供试2个优选的甜仁山杏品系胚褐变率低,半致死温度（LT50）较对照低0．51～0．94℃。供试5个品系抗寒性的顺序依次为山甜1〉山甜2〉山苦1、山苦2〉“优一”。     

实验动物屏障系统微生物动态状况

目的研究运行中的实验动物屏障系统微生物的情况。方法采用沉降菌法、棉拭子法等方法,研究运行中的屏障系统不同区域、不同环境指标下屏障系统内微生物的状况。结果动态下的屏障系统微生物情况与国标GB14925-2001中静态环境有较大不同,动物饲养室和动物实验室沉降菌浓度远高于静态要求;辅助区域在规范化消毒及严格管理的情况下,能达到国标要求。屏障系统的微生物情况存在一定的昼夜变化规律,在晚间出现峰值。结论合适的换气次数可有效控制实验动物屏障系统的沉降菌浓度;加强消毒及硬件的管理,是屏障系统内环境稳定的保障。