文 / 王不留（微信公众号：王不留）
昨天有位朋友微信问我一段翻译。当时一直在开会，今日清早研究了一番。
大家提出问题，共同探讨是一件很有意思的事情。
这其实是2021年3月20号刊《经济学人》的一篇文章。
这段内容是这样的：
That sparsity suggested the genome in question did not belong to a free-living organism. And, with the benefit of further expeditions to the lake, Dr Graf and Dr Milucka now know that it is actually the DNA of a novel bacterium that is well on the way to becoming an organelle, and is hosted by a previously undescribed species of ciliate. Moreover, this bacterium-cum-organelle's free-living ancestor appears to have taken up residence in the ancestors of its ciliate hosts only 200m years ago. It thus provides a snapshot of the process by which mitochondria themselves formed. It has also proved a success. Nitrate-breathing ciliates related to the one in Lake Zug have spread across the globe. A comparison conducted by Dr Graf and Dr Milucka of DNA samples in a genetic database has revealed closely related species as far afield from Switzerland as the lakes of East Africa's Great Rift Valley.
接下来，我做个翻译和解释。
That sparsity suggested the genome in question（被提及的，讨论中的） did not belong to a free-living （独立生存的）organism.
这种稀疏性表明，所讨论的基因组不属于自由生命体。
And, with the benefit of （得益于）further expeditions to the lake, Dr Graf and Dr Milucka now know that it is actually the DNA of a novel bacterium that is well on the way to（去……的路上） becoming an organelle（细胞器）, and is hosted by a previously undescribed species of ciliate（纤毛虫）. (斜线是bacterium的定语从句)
而且，得益于对该湖的进一步考察，格拉夫博士和米卢卡博士现在知道，它实际上是一种新细菌的DNA，而且新细菌正朝着成为一种细胞器的方向发展，并寄生于一种以前未被描述的纤毛虫物种。
在与朋友讨论时，产生一个问题：
在本段，host是动词且是被动语态，is hosted by 不是被寄生的意思吗？
不是的。这应该是“寄生于”。我们先要理清楚host的意思。
host 用作名词时，有多种含义，其中，在生物学里，表示“寄生物的寄主，宿主”的意思。
host 用作动词时，表示“主持，主办”等意思。那么 host 的主语应该是主人，宾语应该是客人。
即 主人 host 客人。（中文意思为：主人招待客人 或 主人接待客人）
反过来就是 客人 be hosted by 主人。
参考文章，就是 a novel bacterium is hosted by a species of ciliate. (新细菌寄生于一种纤毛虫物种)
本段涉及生物知识，补充点相关内容：
植物和动物都是由细胞组成的，细胞内都有细胞核。
微生物中只有真菌具有真正的细胞核和完整的细胞器，故又称真核细胞型微生物。
细菌仅有原始核结构，无核膜和核仁，细胞器很少，属于原核细胞型微生物。
病毒（virus）则没有细胞结构，属于原生微生物。
Moreover, this bacterium-cum-organelle's free-living ancestor appears to have taken up residence in the ancestors of its ciliate hosts only 200m years ago. It thus provides a snapshot of the process by which mitochondria themselves formed. It has also proved a success.
此外，这种细菌兼细胞器的自由生命体的祖先似乎在2亿年前就定居在纤毛虫宿主的祖先那里。因此，它提供了线粒体自身形成过程的快照。它也证明是成功的。
Nitrate-breathing ciliates（专有名词，不知如何翻译） related to the one in Lake Zug have spread across the globe. A comparison conducted by Dr Graf and Dr Milucka of DNA samples in a genetic database has revealed（披露，展现） closely related species as far afield（在远处，远离） from Switzerland as the lakes of East Africa's Great Rift Valley.
与Zug湖中的纤毛虫相关的呼吸硝酸盐的纤毛虫已经遍布全球。格拉夫博士和米卢卡博士在一个基因数据库中对DNA样本进行了比较，结果发现，与瑞士密切相关的物种与东非大裂谷的湖泊一样遥远。
Nitrate-breathing ciliates “呼吸硝酸盐的纤毛虫”仅为字面意思。专有名词，不知如何翻译。
翻译完了，是不是仍然一头雾水？
我就是这样的情况，但这也很正常。主要原因还是缺少相关的知识储备。
公众号没有留言功能。因为才疏学浅，肯定有翻译不准确的地方。
对了，这种生物长啥样？看下图。