Relationships between bacterial productivity and organic carbon at a soil—stream interface

Microbial communities at soil-stream interfaces may be particularly important in regulating amounts and forms of nutrients that leave upland soils and enter stream ecosystems. While microbial communities are thought to be responsible for key nutrient transformations within near-stream sediments, there is relatively little mechanistic information on factors that control microbial activities in these areas. In this study, we examine the roles of dissolved organic carbon (DOC) vs. particulate organic carbon (POC) as potential controls on rates of bacterial productivity (measured as incorporation of [3H]thymidine into bacterial DNA) and amounts of bacterial biomass (measured as fatty acid yield) in sediments along a transect perpendicular to a soil–stream interface. We hypothesized that spatial patterns in bacterial productivity would vary in response to strong and persistent patterns in pore-water concentrations of DOC that were observed along a soil-stream transect throughout a 2-year period. Our results did not support the existence of such a link between pore-water DOC and bacterial productivity. In contrast, we found bacterial productivity and biomass were related to small-scale spatial variations in sediment POC on 3 of 4 sample dates. While our results indicate that total bacterial productivity in near-stream sediments is not consistently linked to spatial variations in pore-water DOC, it is likely that DOC and POC are not mutually exclusive and the relative contribution of DOC and POC to sedimentary microbes varies temporally and spatially in different riparian habitats. This revised version was published online in July 2006 with corrections to the Cover Date.     

The response of a natural phytoplankton community from the Godavari River Estuary to increasing CO2 concentration during the pre-monsoon period

This paper reports for the first time upon the effects of increasing CO₂ concentrations on a natural phytoplankton assemblage in a tropical estuary (the Godavari River Estuary in India). Two short-term (5-day) bottle experiments were conducted (with and without nutrient addition) during the pre-monsoon season when the partial pressure of CO₂ in the surface water is quite low. The results reveal that the concentrations of total chlorophyll, the phytoplankton growth rate, the concentrations of particulate organic matter, the photosynthetic oxygen evolution rates, and the total bacterial count were higher under elevated CO₂ treatments, as compared to ambient conditions (control). δ¹³C of particulate organic matter (POM) varied inversely with respect to CO₂, indicating a clear signature of higher CO₂ influx under the elevated CO₂ levels. Whereas, δ¹³C_POM in the controls indicated the existence of an active bicarbonate transport system under limited CO₂ supply. A considerable change in phytoplankton community structure was noticed, with marker pigment analysis by HPLC revealing that cyanobacteria were dominant over diatoms as CO₂ concentrations increased. A mass balance calculation indicated that insufficient nutrients (N, P and Si) might have inhibited diatom growth compared to cyanobacteria, regardless of increased CO₂ supply. The present study suggests that CO₂ concentration and nutrient supply could have significant effects on phytoplankton physiology and community composition for natural phytoplankton communities in this region. However, this work was conducted during a non-discharge period (nutrient-limited conditions) and the responses of phytoplankton to increasing CO₂ might not necessarily be the same during other seasons with high physicochemical variability. Further investigation is therefore needed.     

基于杂交链式(HCR)反应的甲型流感病毒检测技术研究

甲型流感病毒的现场快速检测对于流感的及时有效防控具有重要意义．本研究基于杂交链式(HCR)反应,利用GO对荧光基团的猝灭作用及共同实现了对甲型流感病毒的快速检测．当目标序列存在时,可引发HCR反应,使短链DNA形成长链,保护FAM荧光基团不被猝灭,从而实现目标物的检测．实验结果表明,该方法在10～40 nmol/L范围内荧光强度与目标检测物浓度表现出了良好的线性关系,检测范围为5～100 nmol/L．这种HCR等温扩增检测技术具有较好的样本检测能力,具有等温、无酶、反应体系简单、操作步骤简便等优点,表现出良好的现场检测应用前景．     

海水颗粒有机碳（POC）变化的生物地球化学机制

海水中颗粒有机碳（POC）的生物地球化学行为是海洋碳循环研究的重要组成部分,近年来的研究取得了重大进展,主要阐述了海水POC生物地球化学研究的概况.海水POC在海洋中的分布受各种物理、化学、生物过程等多种因素的影响.不同海域、不同水层POC的含量与组成差异很大,在水平分布上,近岸高于远海,垂直分布上,表层高于中下层,含量通常为几十到几百个μg/L,主要由陆源碎屑、浮游植物、浮游动物及其新陈代谢产物和死亡残体组成,海水POC可来源于陆源、海源（海洋生物的生产）、海底沉积物的再悬浮以及溶解有机碳（DOC）的转化,其中海源是其主要贡献者.海水POC与生物过程的关系密切,海洋生物既是POC的组成部分也是POC的重要生产者,通过摄食-代谢过程产生碎屑POC,通过垂直洄游促进POC的向下沉降,通过细菌的降解将POC转化为其他形态.POC参与再循环与营养盐（特别是氮、磷、硅）之间有重要的协同作用,生命POC的新陈代谢造成了营养盐浓度的变化,反过来,营养盐浓度的变化又改变了生命POC的组成及数量;无生命的POC一方面在生物及化学作用下分解矿化释放出营养盐,及时补充了水体中氮、磷、硅等生源要素的含量,这在高生产力的珊瑚礁区尤为明显.另一方面,其又通过在沉积物中的矿化,产生吸附位点,吸附营养盐,影响着营养盐在沉积物与水体中的交换.     

Genosensor for rapid,sensitive, specific point-of-care detection of H1N1 influenza (swine flu)

A 5′ amine group-linked haemagglutinin (HA) gene-specific probe was attached over the surface of a working electrode to develop a rapid, specific, and sensitive point of care detection assay for H1N1 (swine flu) in human respiratory nasal swabs. The probe was attached with a cysteine covered screen-printed gold electrode via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS). The electrochemical assay was performed using differential pulse voltammetry with the use of the redox indicator methylene blue for the detection of different concentrations of the single-stranded viral genome. The developed genosensor showed high sensitivity for H1N1 influenza virus with a detection limit of 0.002 ng/6 μL of viral nucleic acid in the sample. Samples were analysed by quantitative real-time Polymerase Chain Reaction as well as by conventional PCR. The genosensor showed high specificity, as no cross-reaction was observed with the heterologous nucleic acid of different pathogens (Salmonella typhi, Neisseria meningitides, and Streptococcus pyogenes) and human DNA, and it was specific for H1N1 with a sensitivity of ∼49 μA cm⁻² ng^-1. Genosensor is based on a very simple methodology that can be followed based on its easy-to-access approach. It is quick and could be used as a point-of-care test for the detection of influenza virus within 30 min.     

糖化血红蛋白标准化及其检测技术的发展

糖尿病已成为继心血管疾病和癌症之后威胁人类健康的三大杀手之一.糖化血红蛋白(glycated hemoglobin,Hb A1c)是反映血糖控制状况的重要指标,可预示并发症发生的风险,具有重要的临床研究价值.美国糖尿病协会(ADA)与世界卫生组织(WHO)于2010~2011年相继推荐其为糖尿病诊断的新标准,并采用Hb A1c≥6.5%作为临床诊断切点.中国关于Hb A1c的研究起步较晚,尚无国家化的标准检测方法,检测质量与国际标准法存在较大差距.同时,由于种群之间的差异性,国际标准所推荐的糖尿病诊断切点,不一定适用于中国人群.为此,本文综述了:a.Hb A1c的测定标准法,简介了国际及国家标准法的发展建立,以及两类标准方法的相互关系;b.Hb A1c的临床检测,概述了亲和层析法、免疫法及酶法在其测定中的应用;c.Hb A1c的即时检测,介绍了数种商业化即时检测仪的信息.旨在为促进国内Hb A1c临床检测技术的发展以及家用化Hb A1c检测仪的设计提供信息支持.     

Application of Short Tandem Repeat markers in diagnosis of chromosomal aneuploidies and forensic DNA investigation in Pakistan

Purpose

Short Tandem Repeat (STR) genetic markers hold great potential in forensic investigations, molecular diagnostics and molecular genetics research. AmpFlSTR® Identifiler™ PCR amplification kit is a multiplex system for co-amplification of 15 STR markers used worldwide in forensic investigations. This study attempts to assess forensic validity of these STRs in Pakistani population and to investigate its applicability in quick and simultaneous diagnosis and tracing parental source of common chromosomal aneuploidies.

Methodology

Samples from 554 healthy Pakistani individuals from 5 different ethnicities were analyzed for forensic parameters using Identifiler STRs and 74 patients' samples with different aneuploidies were evaluated for diagnostic strengths of these markers.

Results

All STRs hold sufficient forensic applicability in Pakistani population with paternity index between 1.5 and 3.5, polymorphic information content from 0.63 to 0.87 and discrimination power ≥ 0.9 (except TPOX locus). Variation from Hardy–Weinberg equilibrium was observed at some loci reflecting selective breeding and intermarriages trend in Pakistan. Among aneuploidic samples, all trisomies were precisely detectable while aneuploidies involving sex chromosomes or missing chromosomes were not clearly detectable using Identifiler STRs. Parental origin of aneuploidy was traceable in 92.54% patients.

Conclusion

The studied STR markers are valuable tools for forensic application in Pakistan and utilizable for quick and simultaneous identification of some common trisomic conditions. Adding more sex chromosome specific STR markers can immensely increase the diagnostic and forensic potential of this system.