铜绿假单胞菌噬菌体PaP4的分离与鉴定

[目的]鉴定一株新分离的铜绿假单胞菌噬菌体PaP4的生物学特性.[方法]双层琼脂培养法制备PaP4的单个噬斑,观察噬斑特点;用聚乙二醇8000浓缩PaP4颗粒后,再用氯化铯密度梯度离心纯化;用透射电子显微镜观察磷钨酸负染色的PaP4颗粒;提取PaP4基因组核酸,通过限制性内切酶图谱分析其核酸类型;按照感染复数(MOI)分别为0.000 1、0.001、0.01、0.1、1和10加入噬菌体纯培养液和宿主菌,充分裂解细菌后,测定噬菌体滴度;以MOI=10的比例加入噬菌体及宿主菌,进行一步生长实验,绘制一步生长曲线.[结果]PaP4的噬斑直径约3 mm-5 mm,圆形透明边缘清晰;PaP4噬菌体呈多面体立体对称的头部,直径约50 nm,有一个约30 nm的短尾;限制性酶切实验表明PaP4基因组为双链DNA;当MOI为0.001时PaP4感染其宿主菌产生的子代噬菌体滴度最高;用一步生长曲线描绘了其生长特性.[结论]PaP4属dsDNA短尾科裂解性噬菌体;最佳感染复数是0.001;由一步生长曲线得出感染宿主菌的潜伏期是25 min,裂解期是20 min,平均裂解量是150.     

中国圈养食蟹猴TrimCyp基因频率

TRIM 5α在绝大部分的旧大陆猴中扮演抗逆转录病毒的角色,能够限制HIV-1的活性。TRIMCyp融合基因是继TRIM 5α后的另一个抗HIV-1因子研究热点。旧大陆猴的TRIMCyp融合基因是由CypA假基因cDNA序列以逆转录转座的方式插入至TRIM5基因的3’非翻译区形成,而且TRIMCyp融合基因在不同灵长类动物中具有地域、基因频率、基因型以及抗逆转病毒效应的差异。虽然食蟹猴TRIMCyp基因的频率在东南亚几个国家或地区已经被初步调查,但是,中国大陆食蟹猴养殖场的TRIMCyp基因频率还没有明确阐明。该研究对中国5个省11个养殖场共1594个食蟹猴(Macaca fascicularis)繁殖种群随机样本的TRIMCyp基因频率进行了筛查研究,发现各场频率略有差异,从7.65%～19.79%不等,显著低于已报道的菲律宾、马来西亚和印度尼西亚来源食蟹猴的TRIMCyp基因频率(34.85%~100%)。该原因可能是由于后者是建立于1978年的封闭群。对带有TRIMCyp融合基因的个体CypA测序发现带有NE单倍型的食蟹猴个体很少,NE单倍型频率(4.93%)显著低于东南亚三个国家食蟹猴的NE单倍型频率(11.1%～14.3%)纯合子。该研究为进一步开展食蟹猴HIV-1动物模型和发病机制提供了基础信息。     

The complete mitochondrial genome sequence analysis of Tibetan argali (Ovis ammon hodgsoni): Implications of Tibetan argali and Gansu argali as the same subspecies

The genus Ovis (Bovidae, Artiodactyla) includes six species, i.e. Ovis ammon, Ovis aries, Ovis canadensis, Ovis dalli, Ovis nivicola and Ovis vignei. Based on morphology, geographical location, habitat, etc., the species O. ammon is divided into nine subspecies. The near threatened Tibetan argali is distributed across the Tibetan Plateau and its peripheral mountains, and believed to be one of the O. ammon subspecies (O. a. hodgsoni). However, considering its morphological features and distributions, a question has been proposed by some researchers about the subspecies status of Tibetan argali. In this study, we employed complete mitochondrial DNA (mtDNA) to explore the phylogenetic relationship and population genetic structure of Tibetan argali. The results revealed that the nucleotide composition, gene arrangement and codon usage pattern of the mitochondrial genome of Tibetan argali are similar to those of other caprines. Phylogenetic analyses showed that Tibetan argali was clustered with O. ammon. Interestingly, five Tibetan argali individuals and one of the three Gansu argali (O. a. dalailamae) individuals were clustered in the same branch, which is a sister group to other two Gansu argali individuals. Together with morphological characteristics, our results suggested that Tibetan argali and Gansu argali may belong to the same subspecies (O. a. hodgsoni) of O. ammon, rather than two different subspecies.     

Response of Heat-Shock Protein (HSP) Genes to Temperature and Salinity Stress in the Antarctic Psychrotrophic Bacterium Psychrobacter sp. G

Temperature and salinity fluctuations are two of the most important factors affecting the growth of polar bacteria. In an attempt to better understand the function of heat-shock proteins (HSPs) in the adaptive mechanisms of the Antarctic psychrotrophic bacterium Psychrobacter sp. G to such conditions, genes Hsp845, Hsp2538, Hsp2666, and Hsp2667 were cloned on the basis of the draft genome. The expression characteristics of these HSP genes under different stress conditions were analyzed by the qRT-PCR method. Expression of Hsp845 and Hsp2667 was inhibited significantly by low temperature (0 and 10 °C, respectively). There was no difference of expression when Hsp2538 and Hsp2666 were exposed to 0 °C but the expression of Hsp2666 was inhibited when exposed to 10 °C. Expression of Hsp2538 and Hsp2667 was not sensitive but expression of Hsp845 and Hsp2666 was increased at low salinity (0 and 15, respectively). Expression of the four HSP genes was enhanced at high salinity (90 and 120) and at high temperature independent of salinity. By contrast, low temperature had no significant effect independent of salinity.     

Characterization and Genome Sequencing of Phage Abp1, a New phiKMV-Like Virus Infecting Multidrug-Resistant Acinetobacter baumannii

While screening for alternative antibiotics against multidrug-resistant Acinetobacter baumannii, we isolated a virulent A. baumannii bacteriophage Abp1. Transmission electron microscopy revealed that the phage had an icosahedral head with a short tail and should be classified as a member of the Podoviridae family. SDS-PAGE showed that Abp1 contained at least one major and nine minor proteins. In a single-step growth test, we demonstrated that Abp1 had a latent period of 10 min and a burst size of 350. Abp1 also had a relatively narrow host range. The entire genome was sequenced, and the final assembly yielded a 42,185 bp, linear, double-stranded DNA molecule with a G+C content of 39.15 % and containing 54 putative genes. Among these genes, 26 were functionally known, leaving 28 unknown putative genes. Abp1 is a new member of the phiKMV-like virus subgroup of the T7 group; its genome sequence is very similar to that of the A. baumannii phage phiAB1.     

A compound‐based computational approach for the accurate determination of hot spots

A plethora of both experimental and computational methods have been proposed in the past 20 years for the identification of hot spots at a protein–protein interface. The experimental determination of a protein–protein complex followed by alanine scanning mutagenesis, though able to determine hot spots with much precision, is expensive and has no guarantee of success while the accuracy of the current computational methods for hot‐spot identification remains low. Here, we present a novel structure‐based computational approach that accurately determines hot spots through docking into a set of proteins homologous to only one of the two interacting partners of a compound capable of disrupting the protein–protein interaction (PPI). This approach has been applied to identify the hot spots of human activin receptor type II (ActRII) critical for its binding toward Cripto‐I. The subsequent experimental confirmation of the computationally identified hot spots portends a potentially accurate method for hot‐spot determination in silico given a compound capable of disrupting the PPI in question. The hot spots of human ActRII first reported here may well become the focal points for the design of small molecule drugs that target the PPI. The determination of their interface may have significant biological implications in that it suggests that Cripto‐I plays an important role in both activin and nodal signal pathways.     

miR-191通过调控C/EBPβ转录影响猪前体脂肪细胞分化

对实验室前期Solexa结果进行深入挖掘,结合生物信息学分析从不同发育阶段猪皮下脂肪组织差异表达的miRNAs中筛选出高丰度差异极显著的候选miR-191.采用腺病毒过表达miR-191,实时定量PCR、Western blot及双荧光素酶报告基因检测等技术方法,初步研究miR-191对猪前体脂肪细胞分化的影响.结果发现,miR-191随着猪前体脂肪细胞的分化表达量逐渐增加.与对照组相比,过表达miR-191的猪前体脂肪细胞中miR-191转录本显著增加,并引起CCAAT增强子结合蛋白β(C/EBPβ)、PPARγ和aP2的mRNA水平降低,抑制了猪前体脂肪细胞分化.同时,Western blot结果显示,与对照组相比过表达miR-191的猪前体脂肪细胞在48 h C/EBPβ蛋白水平下降了55%.更重要的是,通过TargetScan等算法正向筛选以及MicroInspector反向筛选联合获得miR-191候选靶基因,经双荧光素酶报告基因检测结果证实,miR-191可直接作用于C/EBPβ3′UTR,从而降低萤火虫荧光素酶活性.综上所述,miR-191可能通过抑制脂肪细胞分化早期标志基因C/EBPβ的表达,从而抑制了猪前体脂肪细胞的分化.     

水杨酸对高温胁迫下铁皮石斛幼苗耐热性的影响

为研究不同浓度水杨酸对铁皮石斛幼苗耐热性的诱导效应,以移栽半年的铁皮石斛幼苗为实验材料,对不同浓度水杨酸诱导高温胁迫下铁皮石斛幼苗的耐热性进行外观评价及叶绿素、可溶性蛋白质、可溶性糖、丙二醛(MDA)、游离脯氨酸(Pro)含量以及超氧化物歧化酶(SOD)、过氧化酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性的动态测定,观察其动态变化趋势并筛选最佳施用浓度.结果显示:在高温胁迫环境下,随着胁迫时间的延长,不同浓度SA处理均能有效缓解高温对铁皮石斛植株伤害;1.5～2.0 mmol·L1SA处理使铁皮石斛叶片中SOD、POD活性显著提高,0.5～1.5 mmol·L-1 SA处理叶片中CAT、APX活性显著提高;1.5～2.0 mmol·L-1SA处理可显著促进叶片Pro、可溶性糖和可溶性蛋白的积累,有效抑制MDA含量的增加,且不同浓度处理之间差异显著.研究表明,适宜浓度水杨酸处理能提高铁皮石斛幼苗的耐热性,并以1.5 mmol·L-1浓度处理效果最好.     

小叶米仔兰枝条中的抗菌活性成分研究

为探讨小叶米仔兰(Aglaia odorata var.microphyllina)中的抗菌活性成分,从其枝条的乙醇提取物中分离得到6个化合物,通过波谱分析,分别鉴定为:4(15)-桉叶烯-1β,7,11-三醇(1)、4α,10β,11-三羟基-1,5-反-愈创木烷-6-烯(2)、6,15α-环氧-1β,4β-二羟基桉烷(3)、2-羟基-丁二酸-1-甲酯(4)、巴西红厚壳素(5)和胡萝卜苷(6)。以上化合物均为首次从该植物中分离得到,其中化合物1、2、4和5为首次从米仔兰属植物中分离得到。用滤纸片琼脂扩散法测定了化合物1~5的抗菌活性,结果显示化合物4和5对金黄色葡萄球菌有抑制作用。