澳大利亚科学家在南极的湖里发现了一种新的噬病毒体(virophage),这是科学家继Sputnik和Mavirus之后,迄今发现的第三种噬病毒体。新发现有助于科学家更好地理解这类病毒生物功能的复杂性,并解释这类病毒为何能迅速变异以致很难用药物或疫苗抵御它们。研究发表在最新出版的美国《国家科学院院刊》上。
新南威尔士大学微生物学家李嘉图·卡维留里领导的科研小组从南极有机湖中发现了这种新病毒,其基因序列与首个噬病毒体Sputnik非常类似,因此将其归为噬病毒体类,并命名为“有机湖噬病毒体(OLV)”。
科学家在藻DNA病毒的基因序列中发现了OLV,藻DNA病毒是一种攻击海藻的大病毒,而OLV则能通过攻击这些藻DNA病毒使海藻躲过藻DNA病毒的攻击并“撒欢似地繁殖”。
2008年,法国科学家发现,从冷冻库分解出来的巨型病毒被一个较小的病毒Sputnik感染,Sputnik能从宿主病毒和其他微生物身上“掠夺”基因,达到显著的基因混合效果,由于这种生活方式类似于噬菌体,科学家将其称为噬病毒体,Sputnik因此成为人们发现的首个噬病毒体。此前,人们只知道病毒能感染细菌,但Sputnik病毒是首个能感染其他病毒的例子。
科学家当时通过对海洋水域所进行的宏基因组学研究发现,存在大量与巨病毒密切相关的基因序列,并认为,应该有大量类似于Sputnik的噬病毒体存在。
本月初,加拿大英属哥伦比亚大学的微生物学家马缇亚斯·菲舍和柯帝士·夏特尔宣布,他们发现了第二种噬病毒体并将其命名为Mavirus。据报道,这种病毒可以攻击到目前为止发现的最大病毒CroV,Mavirus只有在周围有CroV时才活跃起来,而CroV周围出现Mavirus时,其传染速度会降低。研究人员推测,Mavirus能通过窃取CroV的基因而快速繁殖。
第三种噬病毒体OLV的发现使得科学家更加坚信,在其他很多地方,比如冰湖附近的水域中,都可能存在基因序列与OLV相同的噬病毒体,未来科学家或许可以一一发现。目前,对噬病毒体的研究还处于起步阶段,研究结果将有助于科学家更好地理解这些病毒生物功能的复杂性。(生物谷Bioon.com)
生物谷推荐原文出处:
Proceedings of the National Academies of Sciences doi:10.1073/pnas.1018221108
Virophage control of antarctic algal host–virus dynamics
Sheree Yaua, Federico M. Lauroa, Matthew Z. DeMaerea, Mark V. Browna, Torsten Thomasa,b, Mark J. Rafteryc, Cynthia Andrews-Pfannkochd, Matthew Lewisd, Jeffrey M. Hoffmand, John A. Gibsone, and Ricardo Cavicchiolia,1
Viruses are abundant ubiquitous members of microbial communities and in the marine environment affect population structure and nutrient cycling by infecting and lysing primary producers. Antarctic lakes are microbially dominated ecosystems supporting truncated food webs in which viruses exert a major influence on the microbial loop. Here we report the discovery of a virophage (relative of the recently described Sputnik virophage) that preys on phycodnaviruses that infect prasinophytes (phototrophic algae). By performing metaproteogenomic analysis on samples from Organic Lake, a hypersaline meromictic lake in Antarctica, complete virophage and near-complete phycodnavirus genomes were obtained. By introducing the virophage as an additional predator of a predator–prey dynamic model we determined that the virophage stimulates secondary production through the microbial loop by reducing overall mortality of the host and increasing the frequency of blooms during polar summer light periods. Virophages remained abundant in the lake 2 y later and were represented by populations with a high level of major capsid protein sequence variation (25–100% identity). Virophage signatures were also found in neighboring Ace Lake (in abundance) and in two tropical lakes (hypersaline and fresh), an estuary, and an ocean upwelling site. These findings indicate that virophages regulate host–virus interactions, influence overall carbon flux in Organic Lake, and play previously unrecognized roles in diverse aquatic ecosystems.