Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
mBio. 2011 Oct 4;2(5). doi: 10.1128/mBio.00180-11. Print 2011.
At this time, about 3,000 different viruses are recognized, but metagenomic studies suggest that these viruses are a small fraction of the viruses that exist in nature. We have explored viral diversity by deep sequencing nucleic acids obtained from virion populations enriched from raw sewage. We identified 234 known viruses, including 17 that infect humans. Plant, insect, and algal viruses as well as bacteriophages were also present. These viruses represented 26 taxonomic families and included viruses with single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), positive-sense ssRNA [ssRNA(+)], and dsRNA genomes. Novel viruses that could be placed in specific taxa represented 51 different families, making untreated wastewater the most diverse viral metagenome (genetic material recovered directly from environmental samples) examined thus far. However, the vast majority of sequence reads bore little or no sequence relation to known viruses and thus could not be placed into specific taxa. These results show that the vast majority of the viruses on Earth have not yet been characterized. Untreated wastewater provides a rich matrix for identifying novel viruses and for studying virus diversity.
At this time, virology is focused on the study of a relatively small number of viral species. Specific viruses are studied either because they are easily propagated in the laboratory or because they are associated with disease. The lack of knowledge of the size and characteristics of the viral universe and the diversity of viral genomes is a roadblock to understanding important issues, such as the origin of emerging pathogens and the extent of gene exchange among viruses. Untreated wastewater is an ideal system for assessing viral diversity because virion populations from large numbers of individuals are deposited and because raw sewage itself provides a rich environment for the growth of diverse host species and thus their viruses. These studies suggest that the viral universe is far more vast and diverse than previously suspected.
目前，已识别出约 3000 种不同的病毒，但宏基因组研究表明，这些病毒只是自然界中存在的病毒的一小部分。我们通过对从原始污水中富集的病毒粒子群体的核酸进行深度测序来探索病毒多样性。我们鉴定出 234 种已知病毒，包括 17 种感染人类的病毒。还存在植物、昆虫和藻类病毒以及噬菌体。这些病毒代表 26 个分类家族，包括具有单链 DNA（ssDNA）、双链 DNA（dsDNA）、正单链 RNA[ssRNA(+)]和 dsRNA 基因组的病毒。可以归入特定分类群的新病毒代表 51 个不同的家族，使未经处理的废水成为迄今为止检查过的最具多样性的病毒宏基因组（直接从环境样本中回收的遗传物质）。然而，绝大多数序列读段与已知病毒几乎没有或没有序列关系，因此无法归入特定分类群。这些结果表明，地球上绝大多数病毒尚未得到描述。未经处理的废水为鉴定新病毒和研究病毒多样性提供了丰富的基质。
目前，病毒学的重点是研究相对较少数量的病毒物种。特定病毒的研究要么是因为它们容易在实验室中繁殖，要么是因为它们与疾病有关。对病毒宇宙的大小和特征以及病毒基因组的多样性缺乏了解，是理解重要问题的障碍，例如新发病原体的起源以及病毒之间基因交换的程度。未经处理的废水是评估病毒多样性的理想系统，因为大量个体的病毒粒子种群被沉积，并且原始污水本身为多种宿主物种的生长提供了丰富的环境，从而为它们的病毒提供了生长环境。这些研究表明，病毒宇宙远比以前怀疑的要广泛和多样。
