A novel C1q-domain-containing protein from Zhikong scallop Chlamys farreri with lipopolysaccharide binding activity

The C1q-domain-containing (C1qDC) proteins are a family of proteins characterized by a globular C1q (gC1q) domain in their C-terminus. They are involved in various processes of vertebrates and supposed to be an important pattern recognition receptor in innate immunity of invertebrates. In this study, a novel member of C1q-domain-containing protein family was identified from Zhikong scallop Chlamys farreri (designated as CfC1qDC) by expressed sequence tag (EST) and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of CfC1qDC was of 777 bp, consisting of a T-terminal untranslated region (UTR) of 62 bp and a 3' UTR of 178 bp with a polyadenylation signal sequence AATAAA and a poly (A) tail. The CfC1qDC cDNA encoded a polypeptide of 178 amino acids, including a signal peptide and a C1q-domain of 158 amino acids with the theoretical isoelectric point of 5.19 and the predicted molecular weight of 17.2 kDa. The C1q-domain in CfC1qDC exhibited homology with those in sialic acid binding lectin from mollusks and C1qDC proteins from higher vertebrates. The typical 10 beta-strand jelly-roll folding topology structure of C1q-domain and the residues essential for effective packing of the hydrophobic core were well conserved in CfC1qDC. By fluorescent quantitative real-time PCR, mRNA transcripts of CfC1qDC were mainly detected in kidney, mantle, adductor muscle and gill, and also marginally detectable in hemocytes. In the bacterial challenge experiment, after the scallops were challenged by Listonella anguillarum, there was a significant up-regulation in the relative expression level of CfC1qDC and at 6 h post-injection, the mRNA expression reached the maximum level and was 4.55-fold higher than that of control scallops. Similarly, the expression of CfC1qDC mRNA in mixed primary cultures of hemocytes stimulated by lipopolysaccharides (LPS) was up-regulated and reached the maximum level at 6 h post-stimulation, and then dropped back to the original level gradually. In order to investigate its function, the cDNA fragment encoding the mature peptide of CfC1qDC was recombined and expressed in Escherichia coli BL21 (DE3). The recombinant CfC1qDC protein displayed a significantly strong activity to bind LIDS from E. coli, although no obvious antibacterial or agglutinating activity toward Gram-negative bacteria E. coli JM109, L. anguillarum and Gram-positive bacteria Micrococcus luteus was observed. These results suggested that CfC1qDC was absolutely a novel member of the C1qDC protein family and was involved in the recognition of invading microorganisms probably as a pattern recognition molecule in mollusk. (c) 2008 Elsevier Ltd. All rights reserved.

Identification and molecular characterization of a peritrophin-like protein from fleshy prawn (Fenneropenaeus chinensis)

Peritrophin, one of the components of the peritrophic matrix, was first isolated from the intestine of insects. It is thought to protect insects from invasion of microorganisms and to stimulate digestion of food. Peritrophin-like proteins have also been found in crustaceans, as a component of the egg layer. In this study, one fragment of the peritrophin-like gene was obtained from fleshy prawn (Chinese shrimp) (Fenneropenaeus chinensis) by panning the T7 phage display library constructed with the shrimp hemocyte cDNA. The total sequence of the peritrophin cDNA was cloned by modified SMART cDNA and LD-PCR methods. The full cDNA is 1048 bp and the deduced protein is composed of 274 amino acids, including 21 amino acid signal peptide, and four peritrophin A domains and the latter three forming three chitin-binding domains. Similarity analysis results showed that the peritrophin-like protein from F chinensis has significant similarities with peritrophin-like and cortical rod proteins from other shrimp. It was inducing expression in hemocytes, heart, stomach, gut, and gills of the infected shrimp, and constitutive expression in the ovaries. No expression signal was detected in the hepatopancreas of either infected or noninfected shrimp. The recombinant peritrophin-like protein has the activity of binding Gram-negative bacteria and strong binding activity to chitin. Therefore, the bacteria and chitin binding activities of the peritrophin-like protein suggest that it may plays a role in immune defense and other physiological resposes. (c) 2005 Elsevier Ltd. All rights reserved.

Identification and characterization of a Cystatin gene from Chinese mitten crab Eriocheir sinensis

Cystatins are a superfamily of proteins as reversible inhibitor of cysteine proteinases which play essential roles in a spectrum of physiological and immunological processes In this study, a novel member of Cystatin superfamily was identified from Chinese mitten crab Enocheir sinensis (designated EsCystain) by expressed sequence tag (EST) analysis and rapid amplification of cDNA ends (RACE) approaches The full-length cDNA of EsCystatin was of 1486 bp, consisting of a 5'-terminal untranslated region (UTR) of 92 bp, a 3' UTR of 1034 bp with a polyadenylation signal sequence AATAAA and a polyA tail, and an open reading frame (ORF) of 360 bp encoded a polypeptide of 120 amino acids with the theoretical isoelectric point of 548 and the predicted molecular weight of 13 39 kDa. A signal Cystatin-like domain (Gly(25) to Lys(112)) was found in the putative amino acid sequences of EsCystatin Similar to other Cystatins, the conserved central Q(70)VVSG(74) motif was located in the Cystatin-like domain of EsCystatin But EsCystatin lacked of signal peptide and disulphide bond. The EsCystatin exhibited homology with the other known Cystatins from invertebrates and higher vertebrates, and it was clustered into Cystatin family 1 in the phylogenetic tree. The mRNA transcripts of EsCystain were mainly expressed in hemolymph, gill, hepatopancreas, gonad and muscle, and also marginally detectable in heart After Listonella anguillarum challenge, the relative expression level of EsCystatin in hemolymph was down-regulated to 0 6-fold (P < 0.05) at 3 h post-challenge. Subsequently, it was up-regulated to 3.0-fold (P < 0.01)at 24 h Afterwards. EsCystatin mRNA transcripts suddenly decreased to original level. After Pichia pastoris GS115 challenge, its mRNA expression level in hemolymph was up-regulated to the peak at 3 h (2 8-fold of that in blank (P < 0 01)) The cDNA fragment encoding the mature peptide of EsCystatin was recombined and expressed in Escherichia coli Rosetta-gami (DE3). The recombinant EsCystatin displayed a promoter inhibitory activity against papain When the concentration of EsCystatin protein was of 300 mu g mL(-1), almost 89% of papain activity could be inhibited. These results collectively suggested that EsCystatin was a novel member of protein in Cystatin family, was a potent inhibitor of papain and involved in immune response versus invading microorganisms. (C) 2010 Elsevier Ltd All rights reserved.

中国明对虾免疫系统中抗氧化相关基因的克隆与表达分析

对虾病害在世界范围内的广泛传播，给水产养殖和沿海农村经济造成了重大损失。深入开展对虾免疫机制研究并在此基础上寻找对虾疾病防治的有效方法已成为当务之急。研究表明，当对虾等甲壳动物受到外界病原刺激时，其体内的吞噬细胞在吞噬活动中会激活磷酸己糖支路的代谢，引起呼吸爆发，产生多种活性氧分子。另外，受到病原侵染的对虾还会产生其他多种免疫反应，这些免疫反应将消耗大量的能量（ATP），产能的呼吸链会加速运转，由此也会引发大量活性氧的产生。这些活性氧分子可以杀灭入侵的病原微生物，但同时由于活性氧分子反应的非特异性，它们也会对宿主的细胞、组织和器官造成严重伤害，进而导致对虾生理机能的损伤和免疫系统的破坏。所以，消除对虾体内因过度免疫反应产生的过量氧自由基将能够增强其抵御病原侵染的能力，提高免疫力。本论文从中国明对虾体内克隆了线粒体型超氧化物歧化酶（mMnSOD）、胞质型超氧化物歧化酶（cMnSOD）、过氧化氢酶（Catalase）和过氧化物还原酶（Peroxiredoxin）等四种与免疫系统相关的抗氧化酶基因，分析了它们的分子结构特征，组织分布及应答不同病原刺激的表达变化模式，并对其中的mMnSOD基因和Peroxiredoxin基因进行了体外重组表达、分离纯化和酶活性分析。 采用RACE技术从中国明对虾血细胞中克隆了两个超氧化物歧化酶（SOD）基因，通过序列比对分析发现，其中一个为mMnSOD基因，另一个为cMnSOD基因。mMnSOD基因的cDNA全长为1185个碱基，其中开放阅读框为660个碱基，编码220个氨基酸，其中推测的信号肽为20个氨基酸。多序列比对结果显示中国明对虾mMnSOD基因的推导氨基酸序列与罗氏沼虾、蓝蟹的推导氨基酸序列同源性分别为88%和82%。Northern blot结果表明，该基因在对虾的肝胰脏、血细胞、淋巴器官、肠、卵巢、肌肉和鳃等组织中均有表达。半定量RT-PCR结果显示，对虾感染病毒3 h时，该基因在血细胞和肝胰脏中的转录水平显著升高。此外，通过构建原核表达载体，本研究对该基因进行了体外重组表达，并对纯化的重组蛋白进行了质谱鉴定和酶活分析。cMnSOD基因的cDNA全长为1284个碱基，其中开放阅读框为861个碱基，编码287个氨基酸。多序列比对结果显示中国明对虾cMnSOD基因的推导氨基酸序列与斑节对虾和凡纳滨对虾的同源性高达98%和94%。组织半定量结果显示，cMnSOD基因在对虾被检测的各个组织中均有表达。 另外，半定量RT-PCR结果表明，对虾感染病毒23h时，该基因在肝胰脏中的转录上升到正常水平的3.5倍；而感染后59 h时，该基因在血细胞中的转录上升到正常水平的2.5倍。 利用根据其他生物过氧化氢酶保守氨基酸序列设计的简并引物，结合RACE技术，从中国明对虾肝胰脏中克隆到了过氧化氢酶基因的部分片段，片段长1725个碱基。多序列比对结果发现目前所得中国明对虾Catalase基因部分片段的推导氨基酸序列与罗氏沼虾和皱纹盘鲍Catalase氨基酸序列的同源性分别达到95%和73%。通过实时荧光定量PCR技术对中国明对虾Catalase基因在各个组织中的分布情况及病毒感染后该基因在血细胞和肝胰脏中的转录变化进行了研究。结果发现，该基因在肝胰脏、鳃、肠和血细胞中表达水平较高，在卵巢、淋巴器官和肌肉中的表达水平相对较弱；感染病毒23 h和37 h时，对虾血细胞和肝胰脏中该基因mRNA的表达量分别出现显著性上升。 依据中国明对虾头胸部cDNA文库提供的部分片段信息，结合SMART-RACE技术，从中国明对虾肝胰脏中克隆到了过氧化物还原酶基因（Peroxiredoxin）， 该基因的cDNA全长为942个碱基，其中开放阅读框为594个碱基，编码198个氨基酸。中国明对虾Peroxiredoxin基因的推断氨基酸序列与伊蚊、文昌鱼和果蝇等Peroxiredoxin基因的推断氨基酸序列同源性分别为77%、76%和73%。其蛋白理论分子量为22041.17 Da，pI为5.17。Northern blot结果表明，Peroxiredoxin基因在对虾的肝胰脏、血细胞、淋巴器官、肠、卵巢、肌肉和鳃等组织中均有表达。实时荧光定量PCR结果显示，弧菌感染后，该基因在对虾血细胞和肝胰脏中的转录水平都有明显变化并且表达模式不同。另外，对该基因进行了体外重组表达，并对纯化的重组蛋白进行了质谱鉴定和酶活性分析。酶活性分析表明，复性后的重组蛋白能在DTT存在的条件下还原H2O2。

两株海藻内生真菌次生代谢产物及其生物活性研究

海洋微生物拥有丰富多样的次生代谢途径，其中海洋生物内生真菌次生代谢产物研究日益受到天然产物化学界的重视。本论文以菌丝体生物量、发酵产物重量、抗菌与细胞毒活性、薄层色谱分析结果以及高效液相色谱分析结果等为评价依据对采自青岛沿海的13株海藻内生真菌在四种液体培养基上的静置发酵产物进行了综合评价，并从中选择了黑曲霉Aspergillus niger EN-13（分离自褐藻囊藻Colpomenia sinuosa）和杂色曲霉A. versicolor EN-7（分离自褐藻鼠尾藻Sargassum thunbergii）两株真菌进行了30升规模发酵（分别采用GPYM培养基和PDB培养）和化学成分的研究，对分离得到的大部分化合物进行了初步的生物活性筛选。 发酵提取物采用常规的硅胶柱层析、反相硅胶柱层析，凝胶Sephadex LH-20柱层析、制备薄层层析、半制备高效液相色谱以及重结晶等分离手段，得到单体化合物。利用各种现代波谱技术(IR、UV、EI-MS、FAB-MS、HR-ESI-MS、1H-NMR、13C-NMR、DEPT、1H-1H COSY、HSQC、HMBC等)并结合化学方法从两种菌株发酵提取物中鉴定了55个化合物的结构。其中从菌株A. niger EN-13分离鉴定了31个化合物，发现9个新化合物，包括2个鞘酯类化合物（AN-1~2）、3个萘并-γ-吡喃酮类化合物（AN-3~5）、3个苯乙基取代的α-吡喃酮类化合物（AN-17, AN-19~20）和1个甾体Diels-Alder加成产物（AN-21），另有1个新的天然环二肽（AN-27）被分离鉴定；从菌株A. versicolor EN-7分离鉴定了24个化合物，发现2个新化合物，为蒽醌AV-12与AV-17，另外，从前一菌株（A. niger EN-13）中鉴定的2个新鞘酯类化合物（AN-1~2）在A. versicolor EN-7中也被再次分离到。 对大部分单体化合物进行了抗菌活性、DPPH自由基清除活性和细胞毒活性测试。结果显示新化合物AN-1、AN-5和AN-20具有弱或中等强度的抑制白色念珠菌生长的活性，AN-4、AN-5、AN-21显示了弱或中等强度的抑制黑曲霉生长的活性，AV-12、AV-17显示了弱的抑制大肠杆菌生长的活性。在DPPH自由基清除活性筛选中，AN-5显示了中等强度的活性，其EC50为109.3 mM，与阳性对照BHT相近（EC50为81.8 mM）。其它部分已知化合物在抗菌和DPPH自由基清除活性的筛选中也显示了弱或中等强度的活性。在针对人肝癌细胞株SMMC-7721和人肺腺癌细胞株A549的体外细胞毒活性筛选中，所测样品均未显示显著活性。

Studies on mass summer mortality of cultured zhikong scallops (Chlamys farreri Jones et Preston) in China

Mass mortalities of cultured zhikong scallops (Chlamys farreri) have occurred each summer in most culture areas of northern China since 1996. Among the hypothesized causes are high culture density, infectious disease and genetic inbreeding. To investigate these potential agents, C. farreri were deployed at three densities (low, medium and high) at three sites (Jiaonan, Penglai and Yantai) in the summer of 2000. Scallops were sampled for survival, growth and histopathology before, during and after a mortality episode. Most of the mortality occurred in July and August, during and toward the later part of the spawning season, when water temperature reached 23-26 degrees C. Final cumulative mortalities reached 85% to 90% at all three sites. Scallops in the medium and high densities had higher initial death rates than did those at the low density. High densities also inhibited growth. Ciliates from the genus Trichodina, larvae of various organisms and anomalous secretions were observed in sections of the gill cavity, with highest prevalence during and at the end of the mortality period. Prokaryotic inclusion bodies were found in the soft tissues, but their prevalence was low and apparently without correlation with mortalities. Genetic analysis with random amplified polymorphic DNA markers showed slightly lower heterozygosity in the cultured stocks (0.301) than in the wild stocks (0.331). It is possible that the mortalities are caused by a combination of several factors such as stress associated with reproduction, high temperature, overcrowding and poor circulation in the growout cages, opportunistic invaders or pathogens, and possibly inbreeding. (c) 2005 Elsevier B.V. All rights reserved.

Antimicrobial screening and active compound isolation from marine bacterium NJ6-3-1 associated with the sponge Hymeniacidon perleve

Twenty-nine marine bacterial strains were isolated from the sponge Hymeniacidon perleve at Nanji island, and antimicrobial screening showed that eight strains inhibited the growth of terrestrial microorganisms. The strain NJ6-3-1 with wide antimicrobial spectrum was identified as Pseudoalteromonas piscicida based on its 16S rRNA sequence analysis. The major antimicrobial metabolite, isolated through bioassay-guide fractionation of TLC bioautography overlay assay, was identified as norharman (a beta-carboline alkaloid) by EI-MS and NMR.

Marine bacteria associated with marine macroorganisms: the potential antimicrobial resources

In order to explore marine microorganisms with medical potential, marine bacteria were isolated from seawater, sediment, marine invertebrates and seaweeds collected from different coastal areas of the China Sea. The antimicrobial activities of these bacteria were investigated. Ethyl acetate extracts of marine bacterial fermentation were screened for antimicrobial activities using the method of agar diffusion. The results showed that 42 strains of the isolates have antimicrobial activity. The proportion of active bacteria associated with marine invertebrates (20%) and seaweeds (11%) is higher than that isolated from seawater (7%) and sediment (5%). The active marine bacteria were assigned to the genera Alteromonas, Pseudomonas, Bacillus and Flavobacterium. The TLC autobiographic overlay assay implied that the antimicrobial metabolites produced by four strains with wide antimicrobial spectrum were different. Due to a competitive role for space and nutrient, the marine bacteria associated with marine macroorganisms (invertebrates and seaweeds) could produce more antibiotic substances. These marine bacteria were expected to be potential resources of natural antibiotic products.

Distribution pattern of marine flagellate and its controlling factors in the central and north part of the Huanghai Sea in early summer

A survey was carried out in the central and north part of the Huanghai Sea (34.5degrees similar to 37.0degreesN, 120.5degrees similar to124.0degreesE) during June 12 similar to 27, 2000. It was found that the abundance of marine flagellate ranged from 45 to 1278 cell/ml, 479 cell/ml in average. Flagellate was more abundant in the central part than in the north part of Huanghai Sea, and the abundance decreased with the increasing distance from the coast, showing a similar distribution pattern with isotherm. Vertically, high density of flagellate was always presented in the bottom of thermocline, and formed a dense accumulation in the central area of the Huanghai Sea Cold Water Mass. The effects of physical and biological factors on the distribution of marine flagellate in early summer were discussed. Water temperature (especially the existence of thermocline) rather than salinity showed significant effect on the distribution pattern of marine flagellate in the Huanghai Sea in early summer. When comparing the abundance of marine flagellate with that of other microorganisms, it revealed a comparatively stable relationship among these organhisms, with a ratio of heterotrophic bacteria: cyanobacteria: flagellate: dinoflagellate: ciliate being 10(5) 10(3):10(2):10(1):10(0).

Bromophenol derivatives from the red alga Rhodomela confervoides

Eight new bromophenol derivatives, 2,3-dibromo-4,5-dihydroxybenzyl methyl sulfoxide (1), 4-(2,3-dibromo-4,5-dihydroxyphenyl)-3-butene-2-one (2), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid (3), 2-(3-bromo-5-hydroxy-4-methoxyphenyl)-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid methyl ester (4), 2-phenyl-3-(2,3-dibromo-4,5-dihydroxyphenyl)propionic acid (5), 4'-methoxy-2",3',3"-tribromo-4",5',5"-trihydroxydiphenylacetic acid (6), and 3-bromo-5-hydroxy-4-methoxyphenylacetic acid (7) and its methyl ester (8), together with a known bromophenol, 3-bromo-5-hydroxy4-methoxybenzoic acid (9), were isolated from the red alga Rhodomela confervoides. Their structures were elucidated by spectroscopic methods including IR, EIMS, FABMS, ESIMS, HRFABMS, HRESIMS, 1D and 2D NMR, and single-crystal X-ray structure analysis. Compounds 1-4, 8, and 9 were found inactive against several human cancer cell lines and microorganisms.

Bromophenols coupled with derivatives of amino acids and nucleosides from the red alga Rhodomela confervoides

Three new bromophenols coupled with pyroglutamic acid derivatives and one bromophenol coupled with deoxyguanosine were obtained from the red alga Rhodomela confervoides. By spectroscopic methods including 2D NMR and single-crystal X-ray structure analysis their structures were elucidated as N-(2,3-dibromo-4,5-dihydroxybenzyl)methyl pyroglutamate (1), N-(2,3-dibromo-4,5-dihydroxybenzyl)pyroglutamic acid (2), N-[3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyllmethyl pyroglutamate (3), and 2-N-(2,3-dibromo-4,5-dihydroxybenzylamino)deoxyguanosine (4), respectively. Compounds 1-4 were evaluated against several microorganisms and human cancer cell lines, but found inactive. To our knowledge this is the first report of bromophenols coupled with amino acid or nucleoside derivatives through the C-N bond.

The characteristics of nutrient removal and inhibitory effect of Ulva clathrata on Vibrio anguillarum 65

To investigate the ecological effect of macroalgae on de-eutrophication and depuration of mariculture seawater, the variation of dissolved inorganic nitrogen (DIN) and phosphate (DIP), the amount of Vibrio anguillarum, and total heterotrophic bacteria in Ulva clathrata culture, as well as on the algal surface, were investigated by artificially adding nutrients and V. anguillarum strain 65 from February to April 2006. The results indicated that U. clathrata not only had strong DIN and DIP removal capacities, but also showed a significant inhibitory effect on V. anguillarum, although not reducing the total heterotrophic bacteria. Vibrio anguillarum 65 dropped from 5 similar to 8 x 10(7) cfu mL(-1) to 10 cfu mL(-1) (clone-forming units per mL) in 10 g L-1 of fresh U. clathrata culture within 2 days; i.e., almost all of the Vibrios were efficiently eradicated from the algal culture system. Our results also showed that the inhibitory effect of U. clathrata on V. anguillarum strain 65 was both DIN- and DIP-dependent. Addition of DIN and DIP could enhance the inhibitory effects of the algae on the Vibrio, but did not reduce the total heterotrophic bacteria. Further studies showed that the culture suspension in which U. clathrata was pre-cultured for 24 h also had an inhibitory effect on V. anguillarum strain 65. Some unknown chemical substances, either released from U. clathrata or produced by the alga associated microorganisms, inhibited the proliferation of V. anguillarum 65.

Characteristics of sulfide corrosion products on 316L stainless steel surfaces in the presence of sulfate-reducing bacteria

It has been found that microbial communities play a significant role in the corrosion process of steels exposed in aquatic and soil environments. Biomineralization influenced by microorganisms is believed to be responsible for the formation of corrosion products via complicated pathways of electron transfer between microbial cells and the metal. In this study, sulfide corrosion products were investigated for 316L stainless steel exposed to media with sulfate-reducing bacteria media for 7 weeks. The species of inorganic and organic sulfides in the passive film on the stainless steel were observed by epifluorescence microscope, environmental scanning electron microscope combined with energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The transformation from metal oxides to metal sulfides influenced by sulfate-reducing bacteria is emphasized in this paper. (c) 2005 Elsevier B.V. All rights reserved.

Experimental warming, not grazing, decreases rangeland quality on the Tibetan Plateau

We investigated experimental warming and simulated grazing ( clipping) effects on rangeland quality, as indicated by vegetation production and nutritive quality, in winter-grazed meadows and summer- grazed shrublands on the Tibetan Plateau, a rangeland system experiencing climatic and pastoral land use changes. Warming decreased total aboveground net primary productivity ( ANPP) by 40 g . m(-2) . yr(-1) at the meadow habitats and decreased palatable ANPP ( total ANPP minus non- palatable forb ANPP) by 10 g . m(-2) . yr(-1) at both habitats. The decreased production of the medicinal forb Gentiana straminea and the increased production of the non- palatable forb Stellera chamaejasme with warming also reduced rangeland quality. At the shrubland habitats, warming resulted in less digestible shrubs, whose foliage contains 25% digestible dry matter ( DDM), replacing more digestible graminoids, whose foliage contains 60% DDM. This shift from graminoids to shrubs not only results in lower- quality forage, but could also have important consequences for future domestic herd composition. Although warming extended the growing season in non- clipped plots, the reduced rangeland quality due to decreased vegetative production and nutritive quality will likely overwhelm the improved rangeland quality associated with an extended growing season.Grazing maintained or improved rangeland quality by increasing total ANPP by 20 - 40 g . m(-2) . yr(-1) with no effect on palatable ANPP. Grazing effects on forage nutritive quality, as measured by foliar nitrogen and carbon content and by shifts in plant group ANPP, resulted in improved forage quality. Grazing extended the growing season at both habitats, and it advanced the growing season at the meadows. Synergistic interactions between warming and grazing were present, such that grazing mediated the warming- induced declines in vegetation production and nutritive quality. Moreover, combined treatment effects were nonadditive, suggesting that we cannot predict the combined effect of global changes and human activities from single- factor studies.Our findings suggest that the rangelands on the Tibetan Plateau, and the pastoralists who depend on them, may be vulnerable to future climate changes. Grazing can mitigate the negative warming effects on rangeland quality. For example, grazing management may be an important tool to keep warming- induced shrub expansion in check. Moreover, flexible and opportunistic grazing management will be required in a warmer future.

宣龙式赤铁矿含矿岩系的成矿过程研究

Xuanlong-type Hematite Deposits, distributed in Xuanhua and Longguang area in Hebei province and hosted in the Changchengian Chuanlinggou Formation of Mesoproterozoic, is an oldest depositional iron deposit characterized by oolitic and stromatolitic hematite and siderite. This thesis made an systematic study of its sedimentary, sedimentology, geochemistry, mineralogy and sequence stratigraphy. Based on above, the mechanism and background of biomineralization are discussed. There are four types of hematite ores including stromatolite, algal oolite, algal pisolite and oncolite. Based on detailed study on ore texture, the authors think both algal oolite and algal pisolite ores are organic texture ores, and related to the role of microorganisms. The process of blue-green algae and bacteria in the Xuanlong basin absorbing, adsorbing and sticking iron to build up stromatolite is the formation process of Xuanlong-type hematite deposit. Researches on ore-bearing series and ore geochemistry show that the enrichment of elements is closely related to the microorganism activities. Fe_2O_3 is enriched in dark laminations of stromatolite with much organic matter and SiO_2 in light laminations with detrital matters. The trace elements, especially biogenic elements, including V, P, Mo are enriched in ores but relatively low in country rocks. The paper also demonstrates on the sequence stratigraphy of hematite deposits and five sequences and twelve systems are divided. The characteristics of sequence stratigraphy show that the deposit-forming location has obviously selectivity and always exists under a transgressive setting. The oxygen isotope in hematite is about -2.2～5.7‰, which is similar to that of Hamlys iron formation of Australia but more negative than that of volcanic or hydrothermal iron deposits characterized by high positive values. The calculation by the result of oxygen isotope analysis shows that the temperature of ancient sea water was 48.53℃. The negative value of carbon isotope from siderite indicates its biogenic carbon source. Meanwhile, the occurrence of seismite in the ore-beds, which indicates the formation of hematite deposits is associated with frequent shock caused by structural movement such as distal volcano or ocean-bottom earthquake etc, show the occurrence of hematite deposits is eventual, not gradual. In shorts, Xuanlong-type hematite deposits were the result of interaction among geological setting of semi-isolated Xuanglong basin, favorable hot and humid climate condition, abundant iron source, microorganism such as algae and bateria as well as the fluctuation of the sea level.