科學家發(fā)現(xiàn)一種存在于全世界海洋中的耐惡劣環(huán)境的微生物擁有一種新穎的逃脫病毒攻擊的策略：它在生命的不同階段之間轉換。
一種名為Emiliana huxleyi的單細胞浮游植物身披碳酸鈣的盔甲,，而且在海洋-大氣二氧化碳系統(tǒng)中扮演著一個重要的角色,，它擁有一種大起大落的生活史。E. huxleyi的暴發(fā)是如此的巨大,，以至于從太空中可以看到海洋上的一片藍綠色區(qū)域,。它的衰落是由病毒感染造成的，而且?guī)缀跄芟麥绲暨@種微生物,。Miguel Frada及其同事報告說,，這種微生物從它熟悉的“二倍體”生命階段（擁有染色體的兩份拷貝）轉變到了一個讓病毒無法攻擊的“單倍體”階段（類似于精細胞和卵細胞）。這種單倍體階段讓E. huxleyi袖手旁觀病毒的攻擊,，直到病毒消退,。
這組作者探索了實驗室中單一和混合的二倍體和單倍體群落如何對病毒做出響應。單倍體階段的生長沒有受到注入病毒的影響,；二倍體的E. huxleyi幾乎被滅絕了,。然而，一個新的單倍體細胞群落從殘余的細胞中誕生,，這組科學家懷疑,，單倍體細胞和多倍體細胞外殼之間差異是免疫力的關鍵。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS published September 29, 2008, doi:10.1073/pnas.0807707105
The “Cheshire Cat” escape strategy of the coccolithophore Emiliania huxleyi in response to viral infection
Miguel Frada, Ian Probert, Michael J. Allen, William H. Wilson, and Colomban de Vargas
The coccolithophore Emiliania huxleyi is one of the most successful eukaryotes in modern oceans. The two phases in its haplodiploid life cycle exhibit radically different phenotypes. The diploid calcified phase forms extensive blooms, which profoundly impact global biogeochemical equilibria. By contrast, the ecological role of the noncalcified haploid phase has been completely overlooked. Giant phycodnaviruses (Emiliania huxleyi viruses, EhVs) have been shown to infect and lyse diploid-phase cells and to be heavily implicated in the regulation of populations and the termination of blooms. Here, we demonstrate that the haploid phase of E. huxleyi is unrecognizable and therefore resistant to EhVs that kill the diploid phase. We further show that exposure of diploid E. huxleyi to EhVs induces transition to the haploid phase. Thus we have clearly demonstrated a drastic difference in viral susceptibility between life cycle stages with different ploidy levels in a unicellular eukaryote. Resistance of the haploid phase of E. huxleyi provides an escape mechanism that involves separation of meiosis from sexual fusion in time, thus ensuring that genes of dominant diploid clones are passed on to the next generation in a virus-free environment. These “Cheshire Cat” ecological dynamics release host evolution from pathogen pressure and thus can be seen as an opposite force to a classic “Red Queen” coevolutionary arms race. In E. huxleyi, this phenomenon can account for the fact that the selective balance is tilted toward the boom-and-bust scenario of optimization of both growth rates of calcifying E. huxleyi cells and infectivity of EhVs.
