据物理学家组织网报道，英属哥伦比亚大学(UBC)已经发现世界上最大、最复杂的海洋病毒，Cafeteria roenbergensis病毒主要感染那些吃海洋生态系统中非常重要和分布广泛的浮游生物的掠食者。
这种病毒的基因组比一些细胞生物的基因组还大，它的遗传复杂性使科学家感到疑惑，不知道该把它归为“无生命”生物，还是“有生命”生物行列。海洋微生物学和环境病毒学专家、这项研究的第一论文作者和英属哥伦比亚大学教授柯蒂斯苏特勒说：“我们一般认为病毒都很小，是简单生物体，只有少量基因。然而我们在这种病毒里发现的大量遗传机制，只能在有生命的细胞生物体里找到，它们需要很多基因才能产生DNA、RNA、蛋白质和糖。”
该研究成果发表在本周的《美国国家科学院院刊》上。一般情况下，病毒在活宿主细胞外无法自我复制，它们需要利用宿主提供的蛋白质进行复制，自我复制形式是区分“无生命”和“有生命”生物的分界线。然而最新发现的这种巨型病毒却对上述归类标准发起了挑战，它们虽然仍需要一个细胞进行复制，但它们是在自己的基因组里进行编码的。
20世纪90年代初，有人在德克萨斯州沿海水域发现这种巨型海洋病毒。苏特勒和他的科研组确定该病毒的基因组含有大约73万个碱基对。这使Cafeteria roenbergensis病毒成为目前已知的世界最大海洋病毒和第二大病毒，排名仅次于淡水病毒――多噬棘阿米巴模仿病毒，后者拥有120万个碱基对。Cafeteria roenbergensis病毒还感染在海洋食物链中处于重要地位的浮游动物。
苏特勒说：“尽管这些海洋浮游生物的掠食行为在海洋和淡水系统的碳转移及营养循环过程中起着重要作用，但是我们对该病毒在这个系统里所扮演的角色几乎一无所知。毫无疑问，这种病毒可能还是一大组未知但是具有生态重要性的海洋巨型病毒的代表。”
推荐英文摘要：
PNAS doi: 10.1073/pnas.1007615107
Giant virus with a remarkable complement of genes infects marine zooplankton
Matthias G. Fischera, Michael J. Allenb, William H. Wilsonc, and Curtis A. Suttlea,d,e,1
Departments of aMicrobiology and Immunology,
dBotany, and
eEarth and Ocean Sciences, University of British Columbia, Vancouver, BC, Canada V6T 1Z4;
bPlymouth Marine Laboratory, Plymouth PL1 3DH, United Kingdom; and
cBigelow Laboratory for Ocean Sciences, West Boothbay Harbor, ME 04575-0475
As major consumers of heterotrophic bacteria and phytoplankton, microzooplankton are a critical link in aquatic foodwebs. Here, we show that a major marine microflagellate grazer is infected by a giant virus, Cafeteria roenbergensis virus (CroV), which has the largest genome of any described marine virus (≈730 kb of double-stranded DNA). The central 618-kb coding part of this AT-rich genome contains 544 predicted protein-coding genes; putative early and late promoter motifs have been detected and assigned to 191 and 72 of them, respectively, and at least 274 genes were expressed during infection. The diverse coding potential of CroV includes predicted translation factors, DNA repair enzymes such as DNA mismatch repair protein MutS and two photolyases, multiple ubiquitin pathway components, four intein elements, and 22 tRNAs. Many genes including isoleucyl-tRNA synthetase, eIF-2γ, and an Elp3-like histone acetyltransferase are usually not found in viruses. We also discovered a 38-kb genomic region of putative bacterial origin, which encodes several predicted carbohydrate metabolizing enzymes, including an entire pathway for the biosynthesis of 3-deoxy-d-manno-octulosonate, a key component of the outer membrane in Gram-negative bacteria. Phylogenetic analysis indicates that CroV is a nucleocytoplasmic large DNA virus, with Acanthamoeba polyphaga mimivirus as its closest relative, although less than one-third of the genes of CroV have homologs in Mimivirus. CroV is a highly complex marine virus and the only virus studied in genetic detail that infects one of the major groups of predators in the oceans.
