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1.
The upper millimeters of sediments are considered major locations of microbial colonization and activity. The goal of our study was to investigate variations of microbial communities in the uppermost sediment layers of the coastal Baltic Sea with emphasis on the complex interplay between microbiology and physico‐chemical sediment properties. We selected a high‐resolution methodological approach that combined the cryolanding sampling technique (spatial resolution of 250 μm) with microsensor‐, spectrophotometric and microscopic analyses. While the oxygen penetration depths in dark conditions ranged from 1.4 mm to 2.6 mm during the study period, this zone expanded by about 1 mm in light and could be divided into three micro‐horizons: (i) an upper zone with a high net O2 production, (ii) an intermediate zone with increased O2 consumption on account of light‐stimulated respiration and (iii) a lower zone with lower O2 consumption. Time‐series experiments revealed a rapid response of the benthic microbial community to altered light intensities. In May and July, the net O2 budget in the porewater of sediments was positive within 35 and 22 min after illumination, respectively, whereas in June O2 production exceeded O2 consumption after 112 min. The thickness of the O2 production and O2 consumption micro‐zones decreased from May to July coinciding with an increase in temperature. In May, sites of enhanced O2 consumption were closely associated with subsurface maxima of microbial numbers and enzymatic activities indicating a tight coupling between photoautotrophic and heterotrophic processes between 1‐ and 2‐mm depth. In June and July, the microbial abundance and enzymatic activity hardly varied with depth. Spatial and temporal microheterogeneity of microbial distribution and activity in O2 gradients was seen as a reflection of the complex interplay between microbiology and physico‐chemical sediment properties.  相似文献
2.
以连云港市对虾养殖池表层沉积物为研究对象,采用Tessier连续萃取法,研究了表层沉积物中重金属(Cu、Zn、Pb、Cd、Cr、As、Mn)的赋存形态和酶(脲酶、碱性磷酸酶、过氧化氢酶、转化酶)活性的相关性。结果表明,重金属Cu和Zn以有机-硫化物结合态为主要的赋存形态,Pb以铁锰氧化物态为主要的赋存形态,Cd以可交换态(平均33.47%)和碳酸盐结合态(平均31.16%)为主要存在形态,Cr和As主要以残渣态存在,Mn的铁锰氧化物态比例最高。脲酶的活性范围为0.45—8.96mg/(g·24h),碱性磷酸酶活性范围为2.45—6.69mg/(g·24h),过氧化氢酶活性范围为0.14—2.36m L/(g·min),转化酶活性范围为0.45—10.45mg/(g·24h)。脲酶活性与Cd、As的可交换态、Cd的碳酸盐结合态、Cu、As的铁锰氧化物态、Zn、Pb、Cd、Mn的有机硫化物态之间显著相关;碱性磷酸酶活性与Zn、Cd的铁锰氧化物态显著相关;过氧化氢酶活性与Cd的可交换态、碳酸盐结合态及残渣态、Cu、Cd、As的铁锰氧化物态、Zn、Pb、Cd、Mn的有机硫结合态之间显著相关;转化酶活性与Cu、Cd、As的可交换态、Cd的碳酸盐结合态、Cu、Cd、As的铁锰氧化物态、Zn、Pb、Cd、Mn的有机硫化物态、Cd、As的残渣态之间显著相关。酶活性可以用来指示海水养殖池沉积物中重金属的形态转化过程。  相似文献
3.
A survey of a Ligurian tourist harbour was carried out during winter 2006 and summer 2007 in order to study the organic matter (OM) turnover through extracellular enzymatic activity. Seawater and sediments were sampled at six stations, three inside the port boundaries, one outside the port and two in an area influenced by the outflow of a minor river (Boate). The seawater showed OM turnover times similar to other oligo-mesotrophic coastal areas, and low concentrations of chlorophyll-a and inorganic nutrients. The sediments, instead, revealed high OM loads and a predominance of proteolysis. A significant reduction of the OM loads was observed in the outside station, indicating that the OM accumulation was due to the structures and activities of the harbour and to the Boate influence. The OM biotic recycling via enzymatic activity was enhanced especially during summer. Although the carbohydrates were probably highly refractory, their turnover was notably faster, due to glycolytic enzymatic activity that was enhanced more than the proteolytic in both the sediment and in the seawater. This suggested that the removal and recycling of OM were potentially efficient, and prevented the shift to eutrophication of the Rapallo harbour area.  相似文献
4.
Seasonal monitoring was carried out to investigate the influence of extracellular enzymatic activity (EEA) on metal speciation and organic matter cycling in the rhizosediment of Spartina maritima . Heavy metal speciation was achieved by the Tessier scheme, and showed a similar pattern of variation of the organic-bound fraction, indicating a decomposition process in progress. Both humic acid and organic matter showed the same seasonal pattern. The basal respiration of the rhizosediments also presented a similar seasonal pattern, indicating a microbial degradation of organic matter. The high organic-bound fraction found in the summer gradually decreased towards the winter. This decrease was found to be related to the increase of activity of peroxidase, β- N -acetylglucosaminidase and protease. Also the activity of sulphatase was found to be related to the depletion on the exchangeable fraction, probably due to sulphide formation and consequent mobilization. The results show an interaction between several microbial activities, affecting metal speciation.  相似文献
5.
Extracellular enzyme activities were compared among surface water, bottom water, and sediments of the Delaware Estuary using six fluorescently labeled, structurally distinct polysaccharides to determine the effects of suspended sediment transport on water column hydrolytic activities. Potential hydrolysis rates in surface waters were also measured for the nearby shelf. Samples were taken in December 2006, 6 months after a major flood event in the Delaware Basin that was followed by high freshwater run-off throughout the fall of 2006. All substrates were hydrolyzed in sediments and in the water column, including two (pullulan and fucoidan) that previously were not hydrolyzed in surface waters of the Delaware estuary. At the time of sampling, total particulate matter (TPM) in surface waters at the lower bay, bay mouth, and shelf ranged between 31 mg l−1 and 48 mg l−1 and were 2 to 20 times higher than previously reported. The presence of easily resuspended sediments at the lower bay and bay mouth indicated enhanced suspended sediment transport in the estuary prior to our sampling. Bottom water hydrolysis rates at the two sites affected by sediment resuspension were generally higher than those in surface waters from the same site. Most notably, fucoidan and pullulan hydrolysis rates in bay mouth bottom waters were 22.6 and 6.2 nM monomer h−1, respectively, and thus three and five times higher than surface water rates. Our data suggest that enhanced mixing processes between the sediment and the overlying water broadened the spectrum of water column hydrolases activity, improving the efficiency of enzymatic degradation of high molecular weight organic matter in the water with consequences for organic matter cycling in the Delaware estuary.  相似文献
6.
研究紫菜抗逆的分子机制,将本实验室克隆的条斑紫菜(Porphyra yezoensis Ueda)锰超氧化物歧化酶(manganese superoxide dismutase,Mn SOD)基因全长cDNA克隆到质粒pET-30c(+)中,构建原核表达载体pET-S,转化大肠杆菌BL21(DE3)表达Mn SOD,表达产物的分子量约为30 KDa.利用不同浓度的Mn~(2+)诱导重组Mn SOD的表达,可以检测到比活力随Mn~(2+)浓度增高而上升的趋势.用重组Mn SOD免疫新西兰大白兔,制备了多克隆抗体,多克隆抗体的效价为1∶8 000.免疫印迹实验(Western Blot)表明该多克隆抗体具有很好的特异性.  相似文献
7.
The extent to which marine organic matter is associated with surfaces and the consequences of such associations for organic matter remineralization are the focus of considerable attention. Since extracellular enzymes operating outside microbial cells are required to hydrolyze organic macromolecules to sizes sufficiently small for substrate uptake, the effects of surface interactions–on enzymes as well as on substrates–for hydrolytic activity also require investigation. We used a simplified laboratory system consisting of a free (dissolved) polysaccharide (pullulan) and the same polysaccharide tethered to agarose beads to restrict mobility, plus the corresponding free enzyme (pullulanase) and the same enzyme sorbed to montmorillonite (Mte), to investigate systematically the consequences of surface associations of enzymes and of substrates on hydrolytic activity. Changes in substrate molecular weight were monitored with time to measure the course of enzymatic hydrolysis. Although hydrolysis of free substrate was nearly complete after 2 min incubation with the free enzymes, the sorbed enzymes also effectively hydrolyzed free substrate, and the data suggest that they retained activity longer in solution compared to the free enzymes. Sorbed enzymes progressively hydrolyzed the free substrate from > 50 kD to lower molecular weights during a 24 h incubation, with a final product distribution on average showing only 1.4% and 10.3% of substrate still in the > 50 kD and 10 kD size classes, while 46.6%, 29.3%, and 12.5% of substrate was in the 4 kD, monomer, and free tag size classes, respectively. This product distribution was very similar to that of the free substrate/free enzyme experiment. Tethering the substrate to agarose beads led to lower substrate release (2–3% of total substrate after 98 h incubation) into solution compared to the free substrate case. For tethered substrates, the state of the enzyme (free or sorbed) measurably affected the molecular weight distribution of the hydrolysis products, with free enzymes producing a higher fraction of high molecular weight hydrolysis products (28.7 ± 5.4% of substrate > 50 kD at the end of the incubation) compared to sorbed enzymes (11.6 ± 2.8% of substrate > 50 kD at the end of the incubation.) Tethered substrates were also hydrolyzed in a sediment slurry from surface sediments from Cape Lookout Bight, North Carolina; 0.1% of total substrate was released by enzymes naturally present in 1 cm3 of sediment after 144 h incubation, demonstrating that the enzymes naturally present in marine sediments are also capable of accessing tethered substrates. These investigations suggest that surface associations of enzymes in marine systems may extend the active lifetime of such enzymes, providing an opportunity for hydrolysis over longer periods of time and producing a different size spectrum of hydrolysis products relative to free enzymes. Furthermore, in well-mixed systems, surface-associated enzymes can hydrolyze substrates whose mobility is restricted, highlighting the importance of processes such as resuspension and bioturbation on organic matter remineralization.  相似文献
8.
The Atacama trench, the deepest ecosystem of the southern Pacific Ocean (ca. 8000 m depth) was investigated during the Atacama Trench International Expedition. Sediments, collected at three bathyal stations (1040–1355 m depth) and at a hadal site (7800 m) were analyzed for organic matter quantity and biochemical composition (in terms of phytopigments, proteins, carbohydrates and lipids), bacterial abundance, biomass and carbon production and extracellular enzymatic activities. Functional chlorophyll-a (18.0±0.10 mg m−2), phytodetritus (322.2 mg m−2) and labile organic carbon (16.9±4.3 g C m−2) deposited on surface sediments at hadal depth (7800 m) reached concentrations similar to those encountered in highly productive shallow coastal areas. High values of bacterial C production and aminopeptidase activity were also measured (at in situ temperature and 1 atm). The chemical analyses of the Atacama hadal sediments indicate that this trench behaves as a deep oceanic trap for organic material. We hypothesize that, despite the extreme physical conditions, benthic microbial processes might be accelerated as a result of the organic enrichment.  相似文献
9.
激素敏感性脂肪酶(hormone sensitive lipase,HSL)和乙酰辅酶A羧化酶(acetyl-CoA carboxylase,ACC)是脂代谢的关键酶,肌肉和肝脏是鱼类脂代谢的主要场所。为研究饥饿过程中这两种酶的作用,本实验采用实时荧光定量PCR技术以及ELISA技术检测了在35 d饥饿过程中这两种酶在大黄鱼肌肉和肝组织中mRNA表达水平和酶活性的变化。结果显示,饥饿胁迫显著降低大黄鱼肌肉和肝组织中脂肪含量,以及脂肪合成关键酶ACC mRNA表达水平(P0.05);显著提高脂肪分解关键酶HSL mRNA表达水平(P0.05)。饥饿胁迫对肌肉和肝组织中HSL和ACC酶活性均有显著影响(P0.05),肌肉和肝组织HSL(相关系数r分别为0.598 2和0.539 6)以及肌肉组织ACC酶活性(r=0.677 7)与对应mRNA表达水平呈中度正相关(0.5r0.8),但ACC酶活性在肝组织与其对应的mRNA表达量呈负相关(r=-0.374 0),提示饥饿胁迫对大黄鱼HSL和ACC的表达存在翻译前和翻译后两种水平的调控。本研究结果可为研究饥饿胁迫对大黄鱼脂类代谢分子层面的影响机制提供依据。  相似文献
10.
中华乌塘鳢(Bostrychus sinensis)属于广盐广温、低氧耐受性强、药用价值高的鱼类,为我国东南沿海重要养殖对象。谷胱甘肽过氧化物酶(glutathione peroxidase,GPx)是生物体内重要的抗氧化酶,能够清除过氧化氢防止机体生物膜氧化受损,研究中华乌塘鳢GPx基因对其养殖及海洋生态研究具有重要意义。利用分子克隆技术获得了中华乌塘鳢GPx7和GPx8(分别命名为BsGPx7和BsGPx8)的cDNA序列。BsGPx7编码186个氨基酸,含有2个半胱氨酸(Cys56和Cys85)催化位点;BsGPx8编码210个氨基酸,含有1个半胱氨酸(Cys109)催化位点。利用RT-PCR方法研究了BsGPx7、BsGPx8基因在中华乌塘鳢组织中的分布表达,以及不同浓度镉离子(7.5,15,30 mg/L)胁迫下BsGPx7、BsGPx8基因的表达量变化。结果显示,BsGPx7和BsGPx8在组织中呈泛在性表达,其中肝脏的表达量最高,其次是鳃和皮肤。不同浓度的镉离子胁迫下,BsGPx7基因在鳃和皮肤中的表达量均显著上调(P<0.05),BsGPx8基因在肝脏、鳃和皮肤中的表达量均显著上调(P<0.05)。成功构建了原核表达载体,表达并纯化获得了BsGPx7重组蛋白(rBsGPx7)。对rBsGPx7在不同温度和pH条件下的酶活性进行了测定,表明rBsGPx7在35℃和pH 8条件下酶活性最高。综上提示,BsGPx7与BsGPx8参与了机体对抗镉离子诱导的氧化应激的过程,可能在抗氧化防御中起一定作用。  相似文献
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