Origin and Phylogeny of Microbes Living in Permanent Antarctic Lake Ice

Abstract The phylogenetic diversity of bacteria and cyanobacteria colonizing sediment particles in the permanent ice cover of an Antarctic lake was characterized by analyses of 16S rRNA genes amplified from environmental DNA. Samples of mineral particles were collected from a depth of 2.5 m in the 4-m-thick ice cover of Lake Bonney, McMurdo Dry Valleys, Antarctica. A rRNA gene clone library of 198 clones was made and characterized by sequencing and oligonucleotide probe hybridization. The library was dominated by representatives of the cyanobacteria, proteobacteria, and Planctomycetales, but also contained diverse clones representing many other microbial groups, including the Acidobacterium/Holophaga division, the Green Non-Sulfur division, and the Actinobacteria. Six oligonucleotide probes were made for the most abundant clades recovered in the library. To determine whether the ice microbial community might originate from wind dispersal of the algal mats found elsewhere in Taylor Valley, the probes were hybridized to 16S rDNAs amplified from three samples of terrestrial cyanobacterial mats collected at nearby sites, as well as to bacterial 16S rDNAs from the lake ice community. The results demonstrate the presence of a diverse microbial community dominated by cyanobacteria in the lake ice, and also show that the dominant members of the lake ice microbial community are found in terrestrial mats elsewhere in the area. The lake ice microbial community appears to be dominated by organisms that are not uniquely adapted to the lake ice ecosystem, but instead are species that originate elsewhere in the surrounding region and opportunistically colonize the unusual habitat provided by the sediments suspended in lake ice. Received: 16 August 1999; Accepted: 28 December 1999; Online Publication: 28 April 2000     

解毒酶基因的克隆及其在大肠杆菌和蓝藻中的表达(英文)

近几年来 ,在明确了杀虫药剂抗性机理的基础上 ,从杀虫药剂抗性的昆虫中分离出高抗性基因 (即解毒酶基因 ) ,将该基因克隆到表达载体 pRL 4 39上 ,得到表达载体 pRL B1,将其转化大肠杆菌HB10 1,获得了可以表达解毒酶基因的转基因工程菌株。同时构建了穿梭表达载体 pDC B1,并转化大肠杆菌HB10 1后 ,在抗生素氨卞霉素 (30 μg/mL)和卡那霉素 (30 μg/mL)平板上挑选阳性克隆 ,将阳性克隆的细胞、蓝藻和结合质粒以三亲结合转移的方式转入蓝藻。斑点杂交、Southern分析结果表明已经获得了Synechococcussp .PCC 794 2转基因工程藻。     

The Mesh of Civilizations in the Global Network of Digital Communication

Conflicts fueled by popular religious mobilization have rekindled the controversy surrounding Samuel Huntington’s theory of changing international alignments in the Post-Cold War era. In The Clash of Civilizations, Huntington challenged Fukuyama’s “end of history” thesis that liberal democracy had emerged victorious out of Post-war ideological and economic rivalries. Based on a top-down analysis of the alignments of nation states, Huntington famously concluded that the axes of international geo-political conflicts had reverted to the ancient cultural divisions that had characterized most of human history. Until recently, however, the debate has had to rely more on polemics than empirical evidence. Moreover, Huntington made this prediction in 1993, before social media connected the world’s population. Do digital communications attenuate or echo the cultural, religious, and ethnic “fault lines” posited by Huntington prior to the global diffusion of social media? We revisit Huntington''s thesis using hundreds of millions of anonymized email and Twitter communications among tens of millions of worldwide users to map the global alignment of interpersonal relations. Contrary to the supposedly borderless world of cyberspace, a bottom-up analysis confirms the persistence of the eight culturally differentiated civilizations posited by Huntington, with the divisions corresponding to differences in language, religion, economic development, and spatial distance.Have social media created a global village that spans cultural differences and traditional borders? For most of the postwar period, research on international alignments was informed by World Systems Theory, an approach that emphasized the influence of North-South economic divisions and East-West ideological divisions [1]. Following the collapse of the Soviet Union, Fukuyama [2] proposed that those divisions had culminated in the triumph of liberal democratic systems, signaling the “end of history.” In The Clash of Civilizations [3], Fukuyama’s mentor, Samuel Huntington, acknowledged that “the fundamental source of conflict in this new world will not be primarily ideological or primarily economic,” but he challenged Fukyama’s prediction of global consensus:The great divisions among humankind and the dominating source of conflict will be cultural. Nation states will remain the most powerful actors in world affairs, but the principal conflicts of global politics will occur between nations and groups of different civilizations. The clash of civilizations will dominate global politics. The fault lines between civilizations will be the battle lines of the future.The world has undergone substantial changes since Huntington made this prediction in 1993, including rapid economic growth in South Asia and South America and global diffusion of social media connecting the world’s population. Moreover, the evidence for Huntington''s theory of international global alignment was largely top-down, based on the political and economic relations among culturally differentiated nation states. The growing availability of digital traces of human communications now makes it possible to revisit Huntington''s thesis by taking a bottom-up view, based on interpersonal interactions among millions of individuals instead of the alignments of state actors. Have these online interactions created a global village that spans not only the old Cold War divisions but Huntington’s cultural fault lines as well?To find out, we used hundreds of millions of anonymized email and Twitter communications among tens of millions of worldwide users to map global patterns of transnational interpersonal communication. We measure the density, not the content, of interpersonal communication, and our findings do not address Huntington’s highly controversial warning of the potential for conflict between cultures. Nevertheless, the observed patterns provide a unique angle on changing global alignments in the Post-Cold War era.Our work builds on a study by Leskovec and Horvitz of the global flows of online Instant Messaging (IM) [4], extending that research in four important ways. First, we measure the density of social ties, not the density of message traffic. The “fault lines of civilizations” are indicated not by the number of messages two people exchange across borders but by the number of individuals in each country who exchange messages with one another. Second, we measure the density of social ties after taking into account differences in language, geo-location, Cold War alignment, economic development, and religion. (NB: In addition to analyzing communication densities between country pairs, Leskovec and Horvitz also measured global properties of the social network among pairs of individuals, but they did not use the latter to analyze social densities between country pairs. They also found that between-country communication densities were highly correlated with language and spatial distance, but they did not measure communication densities relative to the expected density given similarities of language and geo-location.) Third, we use multiple platforms (Yahoo! email and Twitter) to provide greater robustness and to avoid the possibility that our results are artifacts of the idiosyncrasies of a particular service. Twitter differs from email in two ways that are relevant to our study: most email exchanges are dyadic while Twitter messages are publicly visible, and the Twitter platform makes it much easier for users to discover one another, thereby reducing the tendency for online interactions to reflect pre-existing relationships. Fourth, we correct for internet access and market penetration, without which online traffic flows confound the strength of interpersonal ties with the popularity of a given communication medium. By taking into account differences in Internet access and market penetration, we are able to estimate the global network of social ties derived from the interpersonal flows of Internet communications.We measured communication density based on the number of observed bi-directed ties between users in two countries, relative to the maximum possible number of such ties, given the number of users in each country and the number of people with Internet access. (NB: The email analysis was based on anonymized geo-tagged edge lists. Prior to the analysis, the edge lists were anonymized as follows: Individual email accounts were assigned a random numeric identifier, after which the original email addresses were deleted. The email message content was not accessed or used for this study. Other than country, the edge lists we analyzed contained no individually identifiable information. The project was approved by the Cornell University IRB. The Twitter dataset was provided to us already anonymized by the team that collected it [5]. Scripts for the processing of that dataset are available from http://dx.doi.org/10.6084/m9.figshare.1304572.)A bi-directed email tie exists between two users if at least two messages are exchanged, one in each direction. A bi-directed Twitter tie exists if two users each follow the other. We defined pairwise communication density as the ratio between the observed number of bi-directed ties and the number of expected ties, given the number of subscribers and the number of Internet users.We obtained qualitatively similar results for email and Twitter communication densities and therefore report only the combined density measures for the two platforms. We also measured densities net of geographic proximity, shared language, population size, economic development, and colonial history.     

Binding of HIV-1 virions to α4β7 expressing cells and impact of antagonizing α4β7 on HIV-1 infection of primary CD4+ T cells

HIV-1 envelope glycoprotein is reported to interact with α4β7, an integrin mediating the homing of lymphocytes to gut-associated lymphoid tissue, but the significance of α4β7 in HIV-1 infection remains controversial. Here, using HIV-1 strain Ba L, the gp120 of which was previously shown to be capable of interacting with α4β7, we demonstrated that α4β7 can mediate the binding of whole HIV-1 virions to α4β7-expressing transfectants. We further constructed a cell line stably expressing α4β7 and confirmed the α4β7-mediated HIV-1 binding. In primary lymphocytes with activated α4β7 expression, we also observed significant virus binding which can be inhibited by an anti-α4β7 antibody. Moreover, we investigated the impact of antagonizing α4β7 on HIV-1 infection of primary CD4+ T cells. In α4β7-activated CD4+ T cells, both anti-α4β7 antibodies and introduction of shorthairpin RNAs specifically targeting α4β7 resulted in a decreased HIV-1 infection. Our findings indicate that α4β7 may serve as an attachment factor at least for some HIV-1 strains. The established approach provides a promising means for the investigation of other viral strains to understand the potential roles of α4β7 in HIV-1 infection.     

拟核结合蛋白与细菌基因的表达调控

拟核结合蛋白是细菌遗传物质组织和基因表达调控的关键. 细菌基因组压缩为致密的拟核必需有拟核结合蛋白的支撑. 拟核结合蛋白、DNA超螺旋和大分子簇在拟核的结构形成中起到重要作用,其中拟核结合蛋白最重要.拟核结合蛋白还影响细菌DNA的复制、重组、转录和修复等多个重要生理过程.作为全局调控因子,拟核结合蛋白是调控细菌适应环境变化所需基因表达的关键. 本文总结拟核结合蛋白的结构、功能和调控,特别是其在致病与非致病分枝杆菌中的差别,为寻找新药物靶标提供线索.     

心脏起搏器程控与遥测系统的研究

目的通过搭建一个心脏起搏器程控与遥测的实验平台,研究高效的程控遥测方案。方法系统由计算机显示终端、FPGA开发板、无线传输硬件电路构成。讨论除无线传输硬件电路之外的设计：计算机显示终端主要实现发送程控命令和显示遥测数据;FPGA开发板分别模仿程控仪和心脏起搏器,主要实现程控遥测信息的编码、解码和纠错功能。结论本系统提出了一种脉冲位置调制（PPM）编码方式——多位PPM编码方式,用于产生包含信息的脉冲波。该方法可以提高无线通讯的传输效率,若应用于植入式心脏起搏器,可延长其电池的使用寿命。实际测试结果证实了本方案的可行性。     

苜蓿盲蝽气味分子结合蛋白AlinOBP2结合特性初步分析

昆虫具有灵敏的嗅觉系统,能够特异性地识别性信息素和寄主挥发物来进行寻找配偶、定位寄主植物和产卵位点.气味分子结合蛋白在昆虫嗅觉识别过程中发挥关键作用.本研究表达和纯化了一个新的苜蓿盲蝽气味分子结合蛋白AlinOBP2,采用qRT-PCR方法解析了AlinOBP2基因的表达谱,结果表明AlinOBP2绝大部分在触角中表达,且在雌雄触角中的表达量相当,在头部也有少量的表达.以N-phenyl-1-naphthylamine（1-NPN）为荧光探针,采用荧光竞争结合实验研究了5种性信息素类似物和13种棉花挥发物与AlinOBP2蛋白的结合能力.结果显示,5种性信息素类似物均不能和AlinOBP2有效结合,暗示AlinOBP2在苜蓿盲蝽寻找配偶过程中不发挥作用.在13种棉花挥发物中,庚酸乙酯和AlinOBP2的结合能力最强,结合常数为9.22μmol/L.二甲基萘、3-己酮、乙酸叶醇酯、乙酸壬酯、香芹醇5种化合物和AlinOBP2结合能力一般,结合常数分别为15.49,17.31,21.53,18.86和13.47μmol/L.据此推测,AlinOBP2可能为普通气味结合蛋白,能够选择性地结合某些棉花挥发物并参与苜蓿盲蝽识别普通气味过程.