法国科学家在最新一期英国《自然》（Nature）杂志上发表报告说，他们在单细胞生物阿米巴变形虫体内发现了两种新型病毒，其中一种体积“巨大”，堪称目前世界上最大的病毒。
法国国家科研中心微生物专家伯纳德·拉斯科拉和迪迪埃·拉乌尔在报告中说，两种新型病毒都是在寄生于空调系统冷却水管道里的阿米巴变形虫体内发现的。其中一种名叫Mimivirus，比一般病毒大出很多，体积几乎与小型细菌相仿，用普通显微镜就能够观察到它的存在。而且它的“块头”甚至超过了现在世界上已知的最大病毒——巨病毒，后者在2003年有关军团病的研究中被发现，也寄生在水生阿米巴变形虫体内。
拉斯科拉表示，巨病毒比Mimivirus略小，但两种病毒都属于同一家族。
科学家发现的另一种病毒叫作Sputnik。据拉斯科拉介绍，该病毒依附在Mimivirus身上，有21个基因，它能够破坏宿主Mimivirus的繁殖能力。
科学家指出，这些病毒通常都存在于浮游生物中，因此可能在海洋的营养循环等方面发挥着重要作用。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature，doi:10.1038/nature07218，Bernard La Scola，Didier Raoult
The virophage as a unique parasite of the giant mimivirus
Bernard La Scola1,6, Christelle Desnues1,6, Isabelle Pagnier1, Catherine Robert1, Lina Barrassi1, Ghislain Fournous1, Michèle Merchat2, Marie Suzan-Monti1, Patrick Forterre3,4, Eugene Koonin5 & Didier Raoult1
URMITE, Centre National de la Recherche Scientifique UMR IRD 6236, Faculté de Médecine, Université de la Méditerranée, 27 Boulevard Jean Moulin, 13385 Marseille Cedex 5, France
Climespace, 185 Rue de Bercy, 75012 Paris, France
Biologie Moléculaire du Gène chez les Extrêmophiles, Institut de Génétique et Microbiologie, Bâtiment 409, Université Paris Sud, Centre d'Orsay, 91405 Orsay Cedex, France
Biologie Moléculaire du Gène chez les Extrêmophiles, Département de Microbiologie, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
National Center for Biotechnology Information (NCBI), National Library of Medicine, National Institutes of Health, Building 38A, Room 5N503, 8600 Rockville Pike, Bethesda, Maryland 20894, USA
These authors contributed equally to this work.
Correspondence to: Didier Raoult1 Correspondence and requests for materials should be addressed to D.R. (Email: didier.raoult@gmail.com).
Viruses are obligate parasites of Eukarya, Archaea and Bacteria. Acanthamoeba polyphaga mimivirus (APMV) is the largest known virus; it grows only in amoeba and is visible under the optical microscope. Mimivirus possesses a 1,185-kilobase double-stranded linear chromosome whose coding capacity is greater than that of numerous bacteria and archaea1, 2, 3. Here we describe an icosahedral small virus, Sputnik, 50 nm in size, found associated with a new strain of APMV. Sputnik cannot multiply in Acanthamoeba castellanii but grows rapidly, after an eclipse phase, in the giant virus factory found in amoebae co-infected with APMV4. Sputnik growth is deleterious to APMV and results in the production of abortive forms and abnormal capsid assembly of the host virus. The Sputnik genome is an 18.343-kilobase circular double-stranded DNA and contains genes that are linked to viruses infecting each of the three domains of life Eukarya, Archaea and Bacteria. Of the 21 predicted protein-coding genes, eight encode proteins with detectable homologues, including three proteins apparently derived from APMV, a homologue of an archaeal virus integrase, a predicted primase–helicase, a packaging ATPase with homologues in bacteriophages and eukaryotic viruses, a distant homologue of bacterial insertion sequence transposase DNA-binding subunit, and a Zn-ribbon protein. The closest homologues of the last four of these proteins were detected in the Global Ocean Survey environmental data set5, suggesting that Sputnik represents a currently unknown family of viruses. Considering its functional analogy with bacteriophages, we classify this virus as a virophage. The virophage could be a vehicle mediating lateral gene transfer between giant viruses.
