1► About “virovore” ⾷⽤病毒的⽣物 We already know an organism classification by food source: Carnivore-animals that feed on meat, and Herbivore-animals that feed on plants. Recently, scientists may have discovered the first organism that feeds exclusively on viruses and have added a new category to the classification of the organisms: virovore, which have a virus-only diet. The results of the research were written up in the paper and published in the Proceedings of the National Academy of Sciences (NAS).
现今我们已知一种以⾷物来源的⽣物分类⽅式：⾷⾁动物-以⾁类为⾷的动物、⾷草动物-以植物为⾷的动物。⽽近⽇，科学家们发现了第⼀种专门以病毒为⾷的⽣物，并在⽣物分类⾥新增了⼀个类别：⾷病毒⽣命体。这项研究成果被写成论⽂，发表在了美国国家科学院(NAS)的刊物上。
This new finding not only fills the gap in food chains and overturns the viral shunt hypothesis, it also revolutionizes human cognition of viruses and the ecological model of existing perceptions, and even influences people’s opinions on global carbon cycling.
这项新发现，不仅填补了⾷物链上的空⽩、推翻了“病毒分流”假说，也彻底改变了⼈类对病毒的认知、改变了⼈们既有认知的⽣态模型，甚⾄影响⼈们对全球碳循环的看法。
A ciliate, or cilia-propelled microorganism, belonging to the genus Halteria. New research led by Nebraska’s John DeLong has revealed that ciliates can feed on water-dwelling viruses — and even grow on a virus-only diet. From: Proyecto Agua via flickr (CC BY-NC-SA 2.0)
2► How did scientists find out virovore Virovore是怎么被发现的 Discussing how did scientists find out virovore, it was actually due to the obsession with “balance” and “integrity” of the researchers. In the existing cognition, it seems that the rampaging viruses have never appeared in the food chain of the dog-eat-dog world. “Viruses are made up of nucleic acids, a lot of nitrogen and phosphorous,” said John DeLong, one of the paper’s authors. “Surely everything should want to eat them.”
⾄于是怎么发现这类⽣物的，还要归功到研究⼈员对“平衡”与“完整”的执着追求。在现有的认识⾥，好像肆虐的病毒从来都没有出现在⾷物链上。论⽂作者之一John DeLong表示：“病毒主要由核酸，⼤量的氮和磷组成，没有⽣物‘吃’它们这不合理。”
Earlier in 1993, Canadian scientist Curtis Suttle had already done some experiments finding that single-celled protists were capable of consuming and digesting viruses, but delved no further to prove it whether deliberately. But professor Suttle always believes the virovore may exist. Recently, John’s research team was studying the chlorovirus (a virus that widely separates in water and often gains access to green algae), and by coincidence, the team inadvertently came up with the hypothesis: do these microorganisms living in water feed specifically on viruses to produce the energy they need itself?
早先在1993年，加拿⼤科学家Curtis Suttle就做过实验发现病毒能够被原⽣⽣物吃进去和消化掉，只是⽆法证明这些病毒是不是被原⽣⽣物刻意捕⾷的。但Suttle教授一直坚信，⾷病毒⽣命体是存在的。近期的John研究团队原本在研究绿藻病毒（⼀种⼴泛分布在活⽔⾥、经常感染绿⾊⽔藻的病毒），⽽在机缘巧合下，团队⾥的⼈不经意提出的假设：⽣活在⽔⾥的这些微⽣物有没有专门以病毒为⾷，来制造⾃⾝所需能量的？
Most organisms may accidentally feed on viruses, but John said he want to see if any organisms would feed exclusively. Further research was then undertaken by the team to find out the query.
⼤部分⽣物可能会在⽆意间误⾷病毒，但John表⽰想要看看有没有⽣物专以病毒为⾷。于是便展开进⼀步研究。
3► Experiments and results 实验与结果
Chlorovirus particles infecting microscopic green algae. From: Kit Lee and Angie Fox
To test the proposed hypothesis, the researchers of John’s team drove out to a nearby pond and collected some water samples containing a large number of microorganisms. Next, they added generous portions of chlorovirus to one sample, and the other keep the original. To confirm that the microorganisms were actually consuming the virus, the team tagged some of the chlorovirus DNA with a fluorescent green dye before it was introduced to the two types of plankton to figure out how the food chain works.
为了验证提出的假设，John团队研究⼈员去附近的池塘采集了⼀些含有⼤量微⽣物的活⽔样本。⼀些池塘⽔作为对照，⼀些池塘⽔加⼊会感染绿藻的氯病毒。为了⽅便观察，John团队还在加⼊主要两种微⽣物之前通过荧光绿⾊染料标记氯病毒DNA，来检查⾷物链的“关系”。
Researchers have discovered that a microbe called "Halteria" frantically devours the virus and thrives. In the water samples that did not contain other food sources, the population of the Halteria was growing an average of about 15 times larger over that same timespan and the number of chloroviruses was plummeting by as much as 100-fold in just two days. Halteria deprived of the chlorovirus, meanwhile, wasn’t growing at all. Paramecium also acts the same. It also used chlorovirus as a source of nutrition. Moreover, this confirmed that viruses were being eaten: the Halteria’s vacuoles – microbial equivalent of stomachs – were glowing green from the feeding, and the fluorescent green mobile traces marked on the chlorovirus DNA.
研究⼈员发现，⼀种名为“Halteria”的微⽣物疯狂吞⾷病毒并茁壮成⻓。在不含有其它⾷物来源的⽔样本中，Halteria的数量在两天内增加了15倍，⽽氯病毒的含量下降到了原来的百分之⼀。⽽在没有氯病毒的对照样本中，Halteria与初始状态相差⽆⼏，其数量并没有明显增加。Paramecium也有类似表现，也同样把氯病毒作为营养来源。并且，发出绿光的Halteria液泡和标记在氯病毒DNA的荧光绿移动痕迹也都证实病毒被“吃掉”了。
Halteria feeds on the Chlorovirus and absorbs viral nutrients to grow
The microbe Halteria is a common genus of protists known to flit about as its hair-like cilia propel it through the water, this kind of ciliate actively feeds on viruses. Some ciliates are only about 100 microns in size, and they may likely be able to sustain growth if enough virus is consumed. Paramecium, On the other hand, is a kind of grass crawler.
这种会主动进⾷病毒的微⽣物“Halteria”是⼀种常⻅的原⽣⽣物属，以其⽑发状纤⽑推动其在⽔中⻜⾏⽽闻名，是纤⽑⾍的⼀种。⼀些纤⽑⾍的⼤⼩就只有100微⽶，这种个头如果能⾷⽤⾜够的病毒是很有可能可以维持⽣⻓所需的。⽽“Paramecium”是⼀种草履⾍。
This suggests that two planktonic organisms, Halteria and Paramecium, can actively eat viruses and thrive. But the differences between these two is that while the Paramecium snacked on the viruses, its sizes and numbers barely budged so it cannot be considered as a virovore. Whereas Halteria, on the other hand, their numbers grew rapidly in just two days. They dined on them, using the chlorovirus as a source of nutrients, they digest and absorb them and ultimately can grow also reproduce normally. So they are the real virovore.
这表明，两种浮游⽣物——“Halteria”和“Paramecium”可以主动⾷⽤病毒并茁壮成⻓。但两者的区别是，虽然“Paramecium”能够吃掉病毒，但它们的数量却没有明显地增⻓，如果只吃病毒的话却不能正常繁衍，因此它们并不能算是专以病毒为⾷的⽣物；⽽“Halteria”的表现却⼤不⼀样，在短短的两天时间⾥它们的数量快速增⻓，它们是真正的专吃病毒的⽣物，⽽且还可以对其进⾏消化和吸收，还能够以此来进⾏正常的⽣⻓和繁衍。
4► A profound finding 颠覆性的发现 According to the above experiments, the researchers finally confirmed that the protozoan Halteria is the first organism discovered by humans to feed on viruses! This discovery is certainly disruptive for biological academia. One of the important breakthroughs was the rejection of the viral shunt hypothesis, which showed that viruses do not completely block the movement of the energy and materials from bacteria up toward the food chain. But are instead consumed by the protists, which continues the flow of energy and materials up toward the food chain. This suggests that the viral shunt hypothesis no longer applies.
通过以上实验，研究者们最终确认，原⾍Halteria，是⼈类发现的第⼀种以病毒为⾷的⽣物！对于⽣物学界来说，这项发现⽆疑是颠覆性的。其中⼀项重要的突破是推翻“病毒分流”的假说，研究表明病毒并不完全会阻碍细菌中的能量和物质⾛向上游⾷物链， 反⽽它还会被原⽣动物⾷⽤，进⽽能量和物质继续在上游⾷物链中流动。这就说明“病毒分流”的假说不再适⽤。
Perhaps in the near future, humans will be able to discover more virovore. Even further, during the studies of virovore, we may find new ways of fighting and eliminating viruses. The researchers indicate that after that they will continue to focus on these questions: How might it shape the structure of food webs? The evolution and diversity of species within them?
或许在不远的将来，⼈类能发现更多的⾷病毒⽣命体。甚⾄进⼀步，在研究⾷病毒⽣命体中，找到对抗和消除病毒的新⽅法。研究⼈员表明，之后他们将继续研究病毒对⾷物链、物种进化等更⼤系统的影响。
Maybe, mankind will defeat viruses and get rid of diseases through continues research…
说不定，⼈类将在不断的研究中战胜病毒，摆脱疾病呢……
5► Reference 参考文献 https://doi.org/10.1073/pnas.2215000120
https://newatlas.com/science/first-virovore-eats-viruses/
https://gizmodo.com/first-lifeform-known-to-eat-viruses-vivovore-1849944677
https://news.unl.edu/newsrooms/today/article/eating-viruses-can-power-growth reproduction-of-microorganism/
https://www.sciencealert.com/an-organism-that-can-dine-exclusively-on-viruses-has been-found-in-a-world-first
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