Biodiversity and biogeography of phages in modern stromatolites and thrombolites

Viruses, and more particularly phages (viruses that infect bacteria), represent one of the most abundant living entities in aquatic and terrestrial environments. The biogeography of phages has only recently been investigated and so far reveals a cosmopolitan distribution of phage genetic material (or genotypes). Here we address this cosmopolitan distribution through the analysis of phage communities in modern microbialites, the living representatives of one of the most ancient life forms on Earth. On the basis of a comparative metagenomic analysis of viral communities associated with marine (Highborne Cay, Bahamas) and freshwater (Pozas Azules II and Rio Mesquites, Mexico) microbialites, we show that some phage genotypes are geographically restricted. The high percentage of unknown sequences recovered from the three metagenomes (>97%), the low percentage similarities with sequences from other environmental viral (n = 42) and microbial (n = 36) metagenomes, and the absence of viral genotypes shared among microbialites indicate that viruses are genetically unique in these environments. Identifiable sequences in the Highborne Cay metagenome were dominated by single-stranded DNA microphages that were not detected in any other samples examined, including sea water, fresh water, sediment, terrestrial, extreme, metazoan-associated and marine microbial mats. Finally, a marine signature was present in the phage community of the Pozas Azules II microbialites, even though this environment has not been in contact with the ocean for tens of millions of years. Taken together, these results prove that viruses in modern microbialites display biogeographical variability and suggest that they may be derived from an ancient community.     

试论我国政府经济职能的科学定位

介绍了政府经济职能的内涵、发达市场经济国家政府经济职能的定位和我国政府经济职能的科学定位，提出了我国经济发展面临的新问题。     

网络环境下的用户信息需求与高校图书馆信息服务

随着计算机技术、通信技术、网络技术的应用，图书馆服务模式发生了巨大变化。在分析传统信息服务模式的基础上，针对高校图书馆用户的信息需求，提出了网络环境下信息服务的新思路。     

水轮机组发电机空气间隙的控制分析

对影响水轮机组空气间隙的因素及其精度进行了分析，提出合理的质量标准，探讨了厂房倾斜等因素对空气间隙的影响及其测量调整方法，以确保空气间隙均匀合格。     

Functional metagenomic profiling of nine biomes

Microbial activities shape the biogeochemistry of the planet and macroorganism health. Determining the metabolic processes performed by microbes is important both for understanding and for manipulating ecosystems (for example, disruption of key processes that lead to disease, conservation of environmental services, and so on). Describing microbial function is hampered by the inability to culture most microbes and by high levels of genomic plasticity. Metagenomic approaches analyse microbial communities to determine the metabolic processes that are important for growth and survival in any given environment. Here we conduct a metagenomic comparison of almost 15 million sequences from 45 distinct microbiomes and, for the first time, 42 distinct viromes and show that there are strongly discriminatory metabolic profiles across environments. Most of the functional diversity was maintained in all of the communities, but the relative occurrence of metabolisms varied, and the differences between metagenomes predicted the biogeochemical conditions of each environment. The magnitude of the microbial metabolic capabilities encoded by the viromes was extensive, suggesting that they serve as a repository for storing and sharing genes among their microbial hosts and influence global evolutionary and metabolic processes.