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1.
有机污染物2,4,6-三氯苯酚(2,4,6-TCP)普遍存在于地下水和河流底泥等厌氧环境中。为了探究厌氧微生物菌群XH-1对2,4,6-TCP的降解能力,本研究以2,4,6-TCP为底物,接种XH-1建立微宇宙培养体系,并以中间产物4-氯苯酚(4-CP)和苯酚为底物分别进行分段富集培养,利用高效液相色谱分析底物的降解转化,同时基于16S rRNA基因高通量测序分析微生物群落结构变化。结果表明: 2,4,6-TCP(122 μmol·L-1)以0.15 μmol·d-1的速率在80 d内被完全降解转化,降解中间产物分别为2,4-二氯苯酚(2,4-DCP)、4-氯苯酚和苯酚,所有中间产物最终在325 d被完全降解。高通量测序结果表明,脱卤杆菌和脱卤球菌可能驱动2,4,6-TCP还原脱氯,其中,脱卤球菌可能在4-CP的脱氯转化中发挥重要作用,并与丁酸互营菌和产甲烷菌联合作用彻底降解2,4,6-TCP。  相似文献   

2.
The signal produced by fluorescence in situ hybridization (FISH) often is inconsistent among cells and sensitivity is low. Small DNA targets on the chromatin are difficult to detect. We report here an improved nick translation procedure for Texas red and Alexa Fluor 488 direct labeling of FISH probes. Brighter probes can be obtained by adding excess DNA polymerase I. Using such probes, a 30 kb yeast transgene, and the rp1, rp3 and zein multigene clusters were clearly detected.  相似文献   

3.
AIMS: To confirm the presence of viable Legionella spp. in dental unit waterlines (DUWL) using fluorescent in situ hybridization (FISH) and compare this method with culture approach and also to validate the utility of an enrichment to increase FISH sensitivity. METHODS AND RESULTS: Water samples from 40 dental units were analysed. Three different techniques for detecting Legionella spp. were compared: (i) culture approach, (ii) direct FISH and (iii) FISH with a previous R2A medium enrichment (R2A/FISH). The FISH detection was confirmed by PCR. The use of the direct FISH does not improve significantly the detection of legionellae when compared with the culture. On the contrary, when R2A/FISH was performed, sensitivity was, respectively, two- and threefold higher than that with the direct FISH and culture approach. Using R2A/FISH, 63% of water samples analysed showed a contamination by legionellae. CONCLUSIONS: Legionellae detection by direct FISH and R2A/FISH in dental unit water is possible but is more rapid and more sensitive (R2A/FISH) than the culture approach. SIGNIFICANCE AND IMPACT OF THE STUDY: R2A/FISH showed that several pathogens present in DUWL are viable but may not be culturable. Unlike PCR, R2A/FISH is designed to detect only metabolically active cells and therefore provides more pertinent information on infectious risk.  相似文献   

4.
Aims:  To detect and enumerate bifidobacteria in faeces with a new quantitative multiplex real-time PCR (qPCR) method and to compare the results obtained with fluorescence in situ hybridization (FISH) methods.
Methods and Results:  A multiplex qPCR assay was developed, which enabled the enumeration of Bifidobacterium spp. by targeting the bifidobacterial xylulose-5-phosphate/fructose-6-phosphate phosphoketolase gene ( xfp ) and total bacteria using universal Eub-primers targeting 16S rRNA gene from the domain bacteria. The qPCR assay showed high sensitivity and specificity and a low detection limit of about 2·5 × 103 bifidobacterial cells per gram of faeces. The qPCR results were compared with FISH combined with microscopy or flow cytometry (FCM). No statistical differences among bifidobacterial counts averages measured in adult faeces with the three methods were observed. Total bacterial count averages were higher with the FISH method coupled with microscopic analyses compared to FISH with FCM, whereas total cell numbers estimated by qPCR were intermediate between the two FISH methods.
Conclusions:  The new qPCR assay was shown to be sensitive, rapid and accurate for enumerating bifidobacteria in faeces.
Significance and Impact of the Study:  This method is a valuable alternative for other molecular methods for detecting faecal bifidobacteria, especially when their counts are below the detection limit of the FISH methods.  相似文献   

5.
基于环介导等温扩增(LAMP)技术建立水产品和养殖水域中灿烂弧菌现场可视化的快速、简便检测方法.以灿烂弧菌等作为研究对象,以灿烂弧菌的toxR基因作为靶基因,确定煮沸法为适合于弧菌基因组DNA提取的快捷方法,优化筛选的引物可以特异地检测灿烂弧菌,检测核酸浓度的灵敏度可以达到10-9g/L,并且结果稳定、可靠.采用该方法...  相似文献   

6.
Laboratory-scale column experiments were performed to investigate the effects of membrane-supplied H2 on tetrachloroethene (PCE) dechlorination and microbial community composition. Columns were filled with aquifer material from one of two TCE-contaminated sites and fed a PCE-spiked anaerobic minimal medium for approximately 1 year. For each experiment, one or more experimental columns were supplied with H2 via gas-permeable hollow-fiber membranes with one control column not receiving any H2. After approximately 1 year of operation, aquifer material samples were collected along the length of the columns. Bacterial communities in the samples were analyzed by amplifying the highly variable V3 region of the 16S rRNA gene and separating amplicons using denaturing gradient gel electrophoresis. Microbial community profiles in H2-fed (continuous or pulsed delivery) columns were compared with those in untreated control columns and microbial community profiles were also compared with dechlorination profiles. Selected bands were sequenced for identification. Supply of the simple electron donor H2, changed the microbial community composition, but did not decrease overall diversity. Continuous H2 addition via hollow-fiber membranes enriched for Dehalococcoides-like species, whose relative abundance correlated with enhanced dechlorination activity. PCE was completely dechlorinated to ethene in columns packed with aquifer material from Cape Canaveral, Florida; PCE was dechlorinated to only cis-dichloroethene, however, in columns packed with aquifer material from a TCE-contaminated wetland near Minneapolis, Minnesota. Unexpectedly, Dehalococcoides-like populations were detected in samples from both sets of column experiments. These results suggest that the mere detection of Dehalococcoides-like species in a sample of aquifer material is not a sufficient indicator of the potential to dechlorinate PCE to ethene via biostimulation by H2.  相似文献   

7.
Fluorescence in situ hybridization (FISH) using rRNA targeted oligonucleotide probes is a standard method for identification of microorganisms in environmental samples. Apart from its value as a phylogenetic marker ribosomal RNA has always been the favoured target molecule for FISH because of its abundance in all cells, whereas plasmids and DNA were regarded as unsuitable targets because of their low copy number. Here we present an improved FISH technique, which is based on polynucleotide probes. It goes beyond the detection of high copy intracellular nucleic acids such as rRNA (up to 10(4)-10(5) copies per cell) and allows for the first time the in situ detection of individual genes or gene fragments on plasmids (10(1)-10(3) copies per cell) and chromosomal DNA (<10 copies per cell) in a single cell. Using E. coli as model organism we were able to detect in situ cells harbouring the antibiotic resistance gene beta lactamase on high, medium and low copy plasmids as well as the chromosomal encoded housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Furthermore, we detected the prepilin peptidase gene xpsO in the plant pathogen Xanthomonas campestris in situ. Because of the characteristic hybridization signal obtained with this method--a halo-like, ring-shaped concentration of fluorescence in the cell periphery--we coined the term RING-FISH (recognition of individual genes) to differentiate it from conventional FISH.  相似文献   

8.
This article describes the continuous on-line monitoring of a dechlorination process by a novel attenuated total reflection-Fourier transform infrared (ATR-FTIR) sensor. This optical sensor was developed to measure noninvasively part-per-million (ppm) concentrations of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CT) in the aqueous effluent of a fixed-bed dechlorinating bioreactor, without any prior sample preparation. The sensor was based on an ATR internal reflection element (IRE) coated with an extracting hydrophobic polymer, which prevented water molecules from interacting with the infrared (IR) radiation. The selective diffusion of chlorinated compound molecules from aqueous solution into the polymer made possible their detection by the IR beam. With the exclusion of water the detection limits were lowered, and measurements in the low ppm level became possible. The best extracting polymer was polyisobutylene (PIB) in the form of a 5.8-microm thick film, which afforded a detection limit of 2, 3, and 2. 5 mg/L (ppm) for TCE, PCE, and CT, respectively. Values of the enrichment factors between the polymer coating and the water matrix of these chloro-organics were determined experimentally and were compared individually with predictions obtained from the slopes of absorbance/concentration curves for the three analytes. Before coupling the ATR-FTIR sensor to the dechlorinating bioreactor, preliminary spectra of the chlorinated compounds were acquired on a laboratory scale configuration in stop-flow and flow-through closed-loop modes. In this way, it was possible to study the behavior and direct response of the optical sensor to any arbitrary concentration change of the analytes. Subsequently, the bioreactor was monitored with the infrared sensor coupled permanently to it. The sensor tracked the progression of the analytes' spectra over time without perturbing the dechlorinating process. To calibrate the ATR-FTIR sensor, a total of 13 standard mixtures of TCE, PCE and CT at concentrations ranging from 0 to 60 ppm were selected according to a closed symmetrical experimental design derived from a 3(2) full-factorial design. The above range of concentrations chosen for calibration reflected typical values during normal bioreactor operation. Several partial least squares (PLS) calibration models were generated to resolve overlapping absorption bands. The standard error of prediction (SEP) ranged between 0.6 and 1 ppm, with a relative standard error of prediction (RSEP) between 3 and 6% for the three analytes. The accuracy of this ATR-FTIR sensor was checked against gas chromatography (GC) measurements of the chlorocompounds in the bioreactor effluents. The results demonstrate the efficiency of this new sensor for routine continuous on-line monitoring of the dechlorinating bioreactor. This strategy is promising for bioprocess control and optimization.  相似文献   

9.
Fluorescence in situ hybridization (FISH) is a powerful technique that is used to detect and localize specific nucleic acid sequences in the cellular environment. In order to increase throughput, FISH can be combined with flow cytometry (flow-FISH) to enable the detection of targeted nucleic acid sequences in thousands of individual cells. As a result, flow-FISH offers a distinct advantage over lysate/ensemble-based nucleic acid detection methods because each cell is treated as an independent observation, thereby permitting stronger statistical and variance analyses. These attributes have prompted the use of FISH and flow-FISH methods in a number of different applications and the utility of these methods has been successfully demonstrated in telomere length determination, cellular identification and gene expression, monitoring viral multiplication in infected cells, and bacterial community analysis and enumeration. Traditionally, the specificity of FISH and flow-FISH methods has been imparted by DNA oligonucleotide probes. Recently however, the replacement of DNA oligonucleotide probes with nucleic acid analogs as FISH and flow-FISH probes has increased both the sensitivity and specificity of each technique due to the higher melting temperatures (T(m)) of these analogs for natural nucleic acids. Locked nucleic acid (LNA) probes are a type of nucleic acid analog that contain LNA nucleotides spiked throughout a DNA or RNA sequence. When coupled with flow-FISH, LNA probes have previously been shown to outperform conventional DNA probes and have been successfully used to detect eukaryotic mRNA and viral RNA in mammalian cells. Here we expand this capability and describe a LNA flow-FISH method which permits the specific detection of RNA in bacterial cells (Figure 1). Specifically, we are interested in the detection of small non-coding regulatory RNA (sRNA) which have garnered considerable interest in the past few years as they have been found to serve as key regulatory elements in many critical cellular processes. However, there are limited tools to study sRNAs and the challenges of detecting sRNA in bacterial cells is due in part to the relatively small size (typically 50-300 nucleotides in length) and low abundance of sRNA molecules as well as the general difficulty in working with smaller biological cells with varying cellular membranes. In this method, we describe fixation and permeabilzation conditions that preserve the structure of bacterial cells and permit the penetration of LNA probes as well as signal amplification steps which enable the specific detection of low abundance sRNA (Figure 2).  相似文献   

10.
In this study, we have established a sensitive semi-nested polymerase chain reaction (PCR) for detection of Nocardia in clinical specimens by first amplifying a 422 bp DNA fragment from the groEL gene, followed by a second amplification of 342 bp DNA by targeting sequences internal to the first amplicon. The semi-nested PCR was evaluated in a murine model of nocardiosis for detection of Nocardia in blood and visceral organs. Healthy BALB/c mice were intravenously infected with 0.2 ml suspension of 2.9 × 105/ml cfu of Nocardia asteroides and N. farcinica. Viable counts and semi-nested PCR were performed post-infection with samples of blood as well as lung, liver, spleen, kidney and brain at 5 minutes, 3 h, and then every 24 h for 3 days. Of the 20 blood samples tested, 15 (75%) were Nocardia positive by culture and 19 (95%) were positive by semi-nested PCR. Likewise, in case of N. asteroides infection, 46% organ samples were positive by culture and 58% by semi-nested PCR. The positivity of organ samples was higher with N. farcinica, 60% by culture and 72% by PCR, which may be attributed to its increased virulence as compared to N. asteroides. These results demonstrate that semi-nested PCR is a rapid and sensitive method for detection of Nocardia in blood and different visceral organs. The diagnostic application of this method provides an additional advantage over culture techniques, as PCR can also detect L-forms of Nocardia in clinical specimens, which otherwise fail to grow on routine isolation medium.  相似文献   

11.
The extent of tetrachloroethene (PCE) dechlorination in two chemostats was evaluated as a function of hydraulic retention time (HRT). The inoculum of these chemostats was from an upflow anaerobic sludge blanket (UASB) reactor that rapidly converts PCE to vinyl chloride (VC) and ethene. When the HRT was 2.9 days, PCE was converted only to cis-dichloroethene (cDCE). When the HRT was 11 days, the end products were VC and ethene. Further studies showed that the dechlorinating microbial community in the UASB reactor contained two distinct populations, one of which converted PCE to cDCE and the other cDCE to VC and ethene. Methanogenic activity was very low in these cultures. The cDCE dechlorinating culture apparently has a lower growth rate than the PCE dechlorinating culture, and as a result, at a shorter HRT, the cDCE dechlorinating culture was washed out from the system leading to incomplete dechlorination of PCE. Both enrichment cultures used pyruvate or hydrogen as electron donors for dechlorination. Acetate was the carbon source (but not energy source) when hydrogen was used. Both cultures had undefined nutrient requirements and needed supplements of cell extract obtained from the mixed culture in the UASB reactor. However, the two cultures were different in their response to the addition of an inhibitor of methanogenesis (2-bromoethanesulfonate [BES]). BES inhibited the dechlorinating activity of the enriched cDCE dechlorinating culture, but had no influence on the PCE dechlorinating culture. Preliminary studies on BES inhibition are presented.  相似文献   

12.
适合的参考基因是应用实时荧光定量PCR (RT-qPCR)技术进行基因表达分析的前提。本研究以7个食用菌常用参考基因(β-TUB 1、GPD、ACTB、Ras、α-TUB、β-TUB 2和SPRYp)为候选基因,利用RT-qPCR检测其在草菇常用生产菌株(CPS)V844、V5、V971和V844继代退化菌株(SDS) T8、T12、T16、T20中的表达;用Genorm、NormFinder和BestKeeper3种软件分析候选基因的表达稳定性,并结合几何平均数法筛选出最佳参考基因。结果表明,SPRYp、α-TUB和β-TUB2基因适用于草菇常用生产菌株检测,SPRYp、GPD和α-TUB基因适用于草菇继代退化检测,SPRYp基因适用于两种条件的检测。两两差异分析表明,草菇常用生产菌株的最佳参考基因组合为SPRYp、α-TUB和β-TUB 2,继代退化菌株的最佳参考基因组合为SPRYp和GPD,两种条件混合菌株的最佳参考基因组合为SPRYp和α-TUB。  相似文献   

13.
桔青毒素(citrinin,CTN)是以玉米、谷物、奶酪等为主要成分的食品和动物饲料中常见的、由桔青霉菌产生的酮类真菌毒素,可引起人和动物的慢性中毒或癌症,一直缺少灵敏的快速检测方法。本文通过指数富集适体系统进化技术(简称SELEX)对可能与CTN结合的特异性适体进行了筛选,经过15轮循环,得到17条适体。通过二级结构分析、亲和力检测发现适体13(Apt-13)对CTN有较好的亲和度,解离常数Kd为0.06μmol/L。进一步利用非荧光标记染料PicoGreen,利用其与双链DNA结合的原理,建立了桔青毒素非标记荧光检测方法,30min完成检测,最低检测限达到国家标准(50ppb)且与其他毒素无交叉反应。本研究建立的基于适体的桔青毒素检测技术成本低,可以替代传统的基于抗体的检测方法,为霉菌毒素的精准检测技术的开发提供了实验证据。  相似文献   

14.
白桦是我国北方重要的造林树种,但其中的高木质素含量严重制约了它作为造纸资源植物的开发利用。本文利用RACE技术获得了白桦咖啡酰辅酶A-3-O-甲基转移酶(CCoAOMT)基因全长ORF序列,并构建了白桦CCoAOMT基因的反义表达载体,通过农杆菌介导法将其导入到白桦中。PCR检测表明反义CCoAOMT基因已整合到白桦的基因组中。对转化植株的半定量PCR检测显示转基因株系的CCoAOMT基因表达量下降;Wiesner染色发现,与野生型相比,转基因植株木质素含量有所下降。对七年生的转基因白桦和野生型对照进行了化学成分分析,结果表明转基因白桦的苯醇抽提物和Klason木质素显著减少,聚戊糖含量升高。上述结果暗示BpCCoAOMT基因参与白桦木质素的合成,反义表达该基因后木质素含量减少,更易于去除。白桦CCoAOMT基因对木质素的合成起重要作用,这为培育低木质素含量的制浆新品种白桦奠定了基础。  相似文献   

15.
A peptide nucleic acid (PNA) probe was developed to detect the toxic dinoflagellate, Takayama pulchella TPXM, using fluorescent in situ hybridization (FISH) combined with epifluorescent microscopy and flow cytometry. The PNA probe was then used to analyze HAB samples from Xiamen Bay. The results indicated that the fluorescein phosphoramidite (FAM)-labeled probe (PNATP28S01) [Flu]-OO ATG CCA TCT CAA GA, entered the algal cells easily and bound to the target species specifically. High hybridization efficiency (nearly 100%) was observed. Detection by epifluorescence microscopy and flow cytometry gave comparable results. The fluorescence intensity of the PNA probe hybridized to T. pulchella cells was remarkably higher than that of two DNA probes used in this study and than the autofluorescence of the blank and negative control cells. In addition, the hybridization condition of the PNA probe was easier to control than DNA probes, and when applied to field-collected samples, the PNA probe showed higher binding efficiency to the target species than DNA probes. With the observed high specificity, binding efficiency, and detection signal intensity, the PNA probe will be useful for monitoring harmful algal blooms of T. pulchella.  相似文献   

16.
Laboratory experiments provide no general answer to the question of whether zooplankton affects cyanobacteria or are affected by prokaryotes. A cyanobacterium may be grazed upon as small colonies, and the same species, as larger colonies, may inhibit zooplankton feeding. Within zooplankton, different species or groups may be affected differently. With this background we set out to detect winter zooplankton grazing and toxicity of overwintering populations of Microcystis aeruginosa. A polymerase chain reaction (PCR) method with oligonucleotide primers for the mcy gene cluster that encodes microcystin synthetase was employed for detection of M. aeruginosa reminiscent products in grazing cladocera. In our field studies, we detected the mcy gene cluster in strains of overwintering colonies of benthic Microcystis and also confirmed the expression of toxicity by quantitative PCR, phosphatase inhibition and enzyme-linked immunosorbent assays (ELISA). We further confirmed the presence of the mcy gene cluster in DNA and RNA isolated from sampled Daphnia magna specimens, indicating that zooplankton in the natural environment may ingest toxic Microcystis cells as part of their diet during winter months.  相似文献   

17.
The low resolution of chromosome‐based Fluorescence in situ hybridisation (FISH) mapping is primarily due to the structure of the plant cell wall and cytoplasm and the compactness of regular chromosomes, which represent a significant obstacle to FISH. In order to improve spatial resolution and signal detection sensitivity, we provide a reproducible method to generate high‐quality extended chromosomes that are ~13 times as long as their pachytene counterparts. We demonstrate that proteinase K used in this procedure is crucial for stretching pachytene chromosomes of Brassica oleracea in the context of a modified Carnoy's II fixative (6:1:3, ethanol:chloroform:acetic acid). The quality of super‐stretched chromosomes was assessed in several FISH experiments. FISH signals from both repetitive 5S rDNA and single‐copy ARC1 on super‐stretched chromosomes are brighter than those on other different types of chromosome due to enhanced accessibility to targets on stretched pachytene chromosomes. In conclusion, the resulting extended chromosomes are suitable for FISH mapping for repetitive DNA sequences and the localisation of a single‐copy locus, and FISH performed on super‐stretched chromosomes can achieve significantly higher sensitivity and spatial resolution than other chromosome‐based FISH mapping techniques.  相似文献   

18.
胡海涛  钱婷婷  杨玲 《植物学报》2022,57(3):320-326
活性氧(reactive oxygen species, ROS)是植物体内的一把“双刃剑”。ROS作为信号分子在植物生命活动中发挥关键作用,但ROS过量积累会对生物大分子造成氧化损伤。准确测定ROS含量对于评估植物细胞内的氧化还原状态至关重要。由于植物体内ROS各组分半衰期短且反应活性强,定性定量检测较为困难。因此,选择合适的检测方法以提高检测的时空准确性非常重要。目前,荧光分析法因其具有灵敏度高、选择性好、检出限低和直观性强等优点,受到研究人员的广泛关注。该文详细描述基于流式细胞仪和激光共聚焦显微镜,利用2′,7′-二氯二氢荧光素二乙酸酯(H2DCFDA)荧光探针检测水稻(Oryzasativa)体内ROS水平和时空分布的操作流程及注意事项。该技术也可用于直接检测拟南芥(Arabidopsis thaliana)、玉米(Zea mays)和大豆(Glycine max)等模式植物组织中ROS的水平和分布。  相似文献   

19.
We describe the application of lamin immunocytochemistry (ICC) and single- or double-target fluorescence in situ hybridization (FISH) on 4 microm thick frozen tissue sections as a method to facilitate scoring of aberrant chromosome copy numbers in colonic tumors. Analysis of FISH signals in colon tissue sections is often hampered by overlap and truncation of epithelial nuclei, due to the density of the epithelial cells. Furthermore, on the basis of nuclear staining it is often difficult to determine whether or not nuclei are overlapping, or adjoining. Therefore, reliable evaluation of (F)ISH signals to screen for genomic changes was until now mainly restricted to isolated nuclei obtained from relatively thick tissue sections. In this study the applicability of lamin ICC, to stain the nuclear periphery and to distinguish individual nuclei, combined with the FISH procedure is explored to solve this problem for colon epithelium. For ICC we applied the alkaline phosphatase (APase)-Fast Red detection method, since the fluorescent precipitate of this reaction resists extensive proteolytic digestion as needed for efficient FISH on tissue sections. Chromosome copy numbers could easily be determined in 4 microm thick frozen tissue sections by combining lamin ICC and FISH. The ratio of the copy numbers of the chromosomes 7 and 17 could be determined in frozen tissue sections after combined lamin ICC and double-target FISH. It is concluded that the combination of lamin ICC and FISH improves chromosome copy number analysis and can be used to investigate genomic changes in different tumor compartments in thin frozen tissue sections.  相似文献   

20.
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