三江平原土壤动物群落多样性对CO2浓度升高的响应

为研究大气CO₂浓度升高条件下土壤动物的响应, 本文采用开顶式气室(OTC)控制大气CO₂浓度, 设置了3个梯度, 分别为低浓度370 ppm背景CO₂ (AC)、中浓度550 ppm CO₂ (EC1)和高浓度700 ppm CO₂ (EC2)。于2017年秋季取样并用改良Tullgren干漏斗法和Baermann湿漏斗分离土壤动物。结果表明: (1)共捕获土壤动物6,268头, 隶属于7纲15目, 优势类群为甲螨亚目, 占捕获量的88.13%; 常见类群为弹尾目和双翅目幼虫, 合计占捕获量的9%。不同CO₂浓度水平下, 优势类群(甲螨亚目)和常见类群(弹尾目、双翅目幼虫)相同, 但是稀有类群存在一定差异。(2) CO₂浓度升高显著增加了甲螨亚目的类群数和个体密度, 显著降低了弹尾目的类群数和个体密度, 对其他土壤动物无显著影响。(3)三江平原不同浓度条件下土壤动物的Shannon-Wiener多样性指数、Pielou均匀度指数均为AC > EC1 > EC2, 而优势度指数为EC2 > EC1 > AC, 丰富度指数为AC > EC2 > EC1。研究表明, 气候变化有可能影响土壤动物的群落结构以及土壤动物的多样性。     

USLE/RUSLE模型中植被因子变化特征及其影响因素

植被因子是USLE/RUSLE模型中最重要的影响因子,其数值变化特征及其影响因素广受关注。以广东省五华县源坑水小流域2011—2013年的径流小区次降雨水沙观测数据为基础,分析了径流小区C值在不同时间尺度的变化特征及其受降雨、植被类型的影响。研究表明:(1)不同时段间C值存在一定波动,其中旱季的C值均大于雨季,夏秋两季的C值较大,且较为接近。各径流小区的C值普遍存在11、8、7月较大,6、5、1月较小的现象,且草本植物C值受植被覆盖度影响较大。(2)降雨量与径流小区C值呈正相关关系,桉树、松树、糖蜜草径流小区C值与次降雨量、各降雨量区间平均值的相关系数分别为0.360**、0.349**、0.291**,0.912*、0.909*、0.822,相较于草本植物,木本植物的C值受降雨影响更大,仅以植被盖度衡量C值有待商榷。(3)相较裸土小区,桉树、松树、糖蜜草小区2011—2013年的土壤流失减幅分别为14.2%、21.5%、23.2%,其C值分别为0.814、0.748、0.772,3种植物中糖蜜草与松树均具有相对较好的水保效益,桉树的水保效益稍逊。     

乙酰肝素酶和CD105在大肠癌中的表达及其相关性

目的探讨乙酰肝素酶和CD105在大肠癌中的表达以及它们之间的关系。方法应用原位杂交方法检测乙酰肝素酶mRNA在95例大肠癌组织中的定位及表达;并用免疫组化方法对全部标本进行CD105染色,记数肿瘤微血管密度(microvesseldensity,MVD);分析乙酰肝素酶mRNA表达与大肠癌浸润、转移和血管生成之间的关系。结果95例大肠癌组织中,乙酰肝素酶mRNA阳性表达49例(51.57%),MVD平均值为(72.1±20.6);阴性表达46例(48.42%),MVD平均值为(41.3±12.4),乙酰肝素酶阳性组MVD表达与阴性组相比有显著性差异(P<0.01)。有浆膜浸润和伴淋巴结转移的大肠癌组织中,乙酰肝素酶mRNA表达阳性率分别为61.42%、63.49%,高于无浆膜浸润(24.00%)和无淋巴结转移组(28.12%),有显著差异(P<0.01)。结论乙酰肝素酶可促进大肠癌的浸润、转移和血管生成,可作为反映大肠癌生物学行为的客观指标。     

象山港网箱养殖区与非养殖区的细菌群落分布

近海集约化养殖是导致我国近海污染的主要来源之一。浮游细菌在近海生态系统的物质循环过程中发挥重要作用,研究海洋浮游细菌群落对养殖活动的响应,对于指示和评价海水养殖生态系统健康具有重要意义。采集了象山港网箱养殖区与非养殖区3个深度,包括表层(0.5 m)、中层(2.5 m)、底层(8.0 m)的水样,利用焦磷酸测序技术测定16S rRNA基因,研究浮游细菌的群落结构和多样性。结果表明:网箱养殖活动不仅使得附近区域水体理化性质发生改变,如化学需氧量浓度显著高于非养殖区域,而且显著地(P0.05)改变了浮游细菌的群落结构,但不同深度间群落结构和多样性的差异不显著。网箱养殖区和非养殖区中主要浮游细菌类群为α-变形菌(Alphaproteobacteria)、γ-变形菌(Gammaproteobacteria)、拟杆菌(Bacteroidetes)、放线菌(Actinobacteria)、β-变形菌(Betaproteobacteria)、ε-变形菌(Epsilonproteobacteria)和其它变形菌(Unclassified Proteobacteria),占细菌总序列数的98.64%。有些细菌类群的平均相对丰度从网箱区到非养殖区差异显著,如拟杆菌(P0.01)和放线菌(P0.05)显著降低,而γ-变形菌(P0.05)显著增加。相似度分析表明γ-变形菌、α-变形菌和拟杆菌是造成网箱区和非养殖区群落差异的主要类群,对群落差异总贡献率达到45.02%。偏冗余分析表明,影响细菌群落分布的主要环境因子有化学需氧量、磷酸盐、铵盐和总有机碳,共解释38.18%的群落变异,空间距离单独解释10.66%的群落变异。实验结果表明,养殖活动导致浮游细菌群落的改变,其中拟杆菌、放线菌和γ-变形菌的丰度显著变化,可能用于评价养殖水体的水质状况。     

Protein 8-class secondary structure prediction using conditional neural fields

Compared with the protein 3-class secondary structure (SS) prediction, the 8-class prediction gains less attention and is also much more challenging, especially for proteins with few sequence homologs. This paper presents a new probabilistic method for 8-class SS prediction using conditional neural fields (CNFs), a recently invented probabilistic graphical model. This CNF method not only models the complex relationship between sequence features and SS, but also exploits the interdependency among SS types of adjacent residues. In addition to sequence profiles, our method also makes use of non-evolutionary information for SS prediction. Tested on the CB513 and RS126 data sets, our method achieves Q8 accuracy of 64.9 and 64.7%, respectively, which are much better than the SSpro8 web server (51.0 and 48.0%, respectively). Our method can also be used to predict other structure properties (e.g. solvent accessibility) of a protein or the SS of RNA.     

Activatable Near-Infrared Fluorescent Probe for In Vivo Imaging of Fibroblast Activation Protein-alpha

Fibroblast activation protein-alpha (FAPα) is a cell surface glycoprotein which is selectively expressed by tumor-associated fibroblasts in malignant tumors but rarely on normal tissues. FAPα has also been reported to promote tumor growth and invasion and therefore has been of increasing interest as a promising target for designing tumor-targeted drugs and imaging agents. Although medicinal study on FAPα inhibitors has led to the discovery of many FAPα-targeting inhibitors including a drug candidate in a phase II clinical trial, the development of imaging probes to monitor the expression and activity of FAPα in vivo has largely lagged behind. Herein, we report an activatable near-infrared (NIR) fluorescent probe (ANP(FAP)) for in vivo optical imaging of FAPα. The ANP(FAP) consists of a NIR dye (Cy5.5) and a quencher dye (QSY21) which are linked together by a short peptide sequence (KGPGPNQC) specific for FAPα cleavage. Because of the efficient fluorescence resonance energy transfer (FRET) between Cy5.5 and QSY21 in ANP(FAP), high contrast on the NIR fluorescence signal can be achieved after the cleavage of the peptide sequence by FAPα both in vitro and in vivo. In vitro assay on ANP(FAP) indicated the specificity of the probe to FAPα. The in vivo optical imaging using ANP(FAP) showed fast tumor uptake as well as high tumor to background contrast on U87MG tumor models with FAPα expression, while much lower signal and tumor contrast were observed in the C6 tumor without FAPα expression, demonstrating the in vivo targeting specificity of the ANP(FAP). Ex vivo imaging also demonstrated ANP(FAP) had high tumor uptake at 4 h post injection. Collectively, these results indicated that ANP(FAP) could serve as a useful NIR optical probe for early detection of FAPα expressing tumors.     

Geographic distance and pH drive bacterial distribution in alkaline lake sediments across Tibetan Plateau

Continent-scale biogeography has been extensively studied in soils and marine systems, but little is known about biogeographical patterns in non-marine sediments. We used barcode pyrosequencing to quantify the effects of local geochemical properties and geographic distance for bacterial community structure and membership, using sediment samples from 15 lakes on the Tibetan Plateau (4-1670?km apart). Bacterial communities were surprisingly diverse, and distinct from soil communities. Four of 26 phyla detected were dominant: Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria, albeit 20.2% of sequences were unclassified at the phylum level. As previously observed in acidic soil, pH was the dominant factor influencing alkaline sediment community structure, phylotype richness and phylogenetic diversity. In contrast, archaeal communities were less affected by pH. More geographically distant sites had more dissimilar communities (r?=?0.443, P?=?0.030). Variance partitioning analysis showed that geographic distance (historical contingencies) contributed more to bacterial community variation (12.2%) than any other factor, although the environmental factors explained more variance when combined (28.9%). Together, our results show that pH is the best predictor of bacterial community structure in alkaline sediments, and confirm that both geographic distance and chemical factors govern bacterial biogeography in lake sediments.     

Sip1Ab gene from a native Bacillus thuringiensis strain QZL38 and its insecticidal activity against Colaphellus bowringi Baly

In this study, we collected 540 soil samples from northeast China and isolated the wild-type strain of Bacillus thuringiensis (Bt) by identifying and cloning 9 Bt strains that expressed the secreted insecticidal protein (Sip) gene. We selected the strain QZL38 for further study. The sip gene was identified from the Bt strain QZL38 using polymerase chain reaction (PCR). We sequenced a 1095-base pair fragment of DNA that encodes 364 amino acid residues of a 41.18?kDa pro-toxin and compared it with the registered Sip1Ab protein amino acid residue sequence. The sequence was submitted to GenBank with the accession no. KP231523, and the gene was named sip1Ab. The Sip1Ab protein expressed in Escherichia coli showed insecticidal activity against Colaphellus bowringi Baly, with an LC50 of 1.051?μg?mL^?1. To identify the active fragment of the Sip1Ab toxin, four pairs of primers with different truncation positions were designed, and the recombinant proteins were expressed in E. coli. The truncated Sip protein expressed in E. coli showed insecticidal activity against C. bowringi Baly. The insecticidal activity of the recombinant proteins against C. bowringi Baly from the Sip1Ab signal peptide after removal of 30 amino acid residues showed an LC50 of 1.078?μg?mL^?1. Sip proteins may play an important role in the prevention and control of the C. bowringi Baly.