Some ancient microbes frozen with Ötzi the Iceman are still growing

与冰人奥茨一同冰封的古老微生物仍在生长

Ötzi the Iceman, Europe’s most famous mummy, is crawling with microbes, some long dead, some still eking out a living after thousands of years, and some very modern. After he died in the Ötztal Alps, the Copper Age man now known as Ötzi lay alone and forgotten for 5,300 years, until a group of hikers stumbled on his freeze-dried remains in 1991. 欧洲最著名的木乃伊——冰人奥茨（Ötzi the Iceman）身上爬满了微生物，其中一些早已死亡，一些在数千年后依然勉强存活，还有一些则是非常现代的品种。这位被称为奥茨的铜石并用时代男子在奥茨塔尔阿尔卑斯山去世后，独自被遗忘了 5300 年，直到 1991 年一群徒步旅行者偶然发现了他的冷冻干燥遗骸。

Since then, he’s received a lot of attention from scientists, who have sequenced his DNA, pored over his last meal and the remains of his gut microbes, and examined his clothes and his broken tools. Today, Ötzi lies in a high-tech resting place at the South Tyrol Museum of Archaeology in Italy, where, it turns out, his body is still home to a handful of cold-adapted yeast species that have probably been with him since just after he died. 自那时起，他受到了科学家的广泛关注。研究人员对他的 DNA 进行了测序，仔细研究了他的最后一餐和肠道微生物残留，并检查了他的衣物和破损的工具。如今，奥茨安放在意大利南蒂罗尔考古博物馆的高科技展柜中。事实证明，他的身体里依然寄居着几种耐寒酵母，这些酵母很可能在他去世后不久就一直伴随着他。

Microbiologist Mohamed S. Sarhan (of the Institute of Mummy Studies at the private Eurac Research center) and his colleagues recently sampled material from Ötzi’s stomach and meltwater from inside his body, swabbed his skin, and even sampled airborne microbes from his frozen storage room and the lab outside it. They also took samples from a block of frozen alpine soil taken from next to Ötzi’s body back in 1991. 微生物学家 Mohamed S. Sarhan（来自私立 Eurac 研究中心的木乃伊研究所）及其同事最近对奥茨的胃部物质和体内融水进行了采样，擦拭了他的皮肤，甚至采集了他冷冻储藏室及其外部实验室空气中的微生物样本。他们还对 1991 年从奥茨遗体旁采集的一块冰冻高山土壤进行了取样。

We already know quite a bit about Ötzi’s gut microbes thanks to a 2019 study, but Sarhan and his colleagues wanted the bigger picture. Instead of just sequencing all the microbial DNA they could find on Ötzi, the researchers wanted to understand which species were really part of his ancient one-man ecosystem and which were modern contaminants. 多亏了 2019 年的一项研究，我们已经对奥茨的肠道微生物有了一定了解，但 Sarhan 和他的同事们希望获得更全面的图景。研究人员没有仅仅对奥茨身上能找到的所有微生物 DNA 进行测序，而是试图弄清楚哪些物种真正属于他古老的“单人”生态系统，哪些是现代污染物。

Ötzi is kept in carefully maintained conditions, as close as possible to the glacier that preserved his body for more than 5,000 years. The chamber is a brisk -6º Celsius, with 99 percent humidity carefully maintained by a spray of UV-treated water. That’s enough to protect the mummy from most of the microbes that usually help decompose human remains. 奥茨被保存在精心维护的环境中，尽可能还原他被冰川保存 5000 多年的原始状态。储藏室温度保持在零下 6 摄氏度，并通过喷洒紫外线处理过的水，将湿度严格控制在 99%。这足以保护木乃伊免受大多数通常会分解人类遗骸的微生物侵害。

But Sarhan and his colleagues were surprised to find that it’s also the perfect environment for a few microbes that Ötzi carried with him down from the mountains. In samples from the mummy, Sarhan and his colleagues found four strains of cold-tolerant yeasts, all closely related to similar yeasts found in Arctic glaciers, in Antarctica, and high in the mountains of Italy and Russia. 但 Sarhan 和他的同事们惊讶地发现，这对于奥茨从山上带下来的一些微生物来说，竟是完美的生存环境。在木乃伊的样本中，研究团队发现了四种耐寒酵母菌株，它们与在北极冰川、南极洲以及意大利和俄罗斯高山中发现的类似酵母亲缘关系密切。

And unlike Ötzi’s long-dead gut bacteria, which left just broken, aging fragments of DNA behind, the yeasts seem to be alive and reproducing (albeit at, ahem, a glacial pace). “These yeasts have accompanied Ötzi on his long journey through the millennia,” said Frank Maxiner, director of the Institute for Mummy Studies at Eurac and a coauthor of the recent study, in a press release. 与奥茨体内早已死亡、只留下破碎且老化的 DNA 片段的肠道细菌不同，这些酵母似乎依然活着并正在繁殖（尽管速度极其缓慢，如同冰川移动一般）。Eurac 木乃伊研究所所长、该研究的合著者 Frank Maxiner 在新闻稿中表示：“这些酵母在数千年的漫长旅程中一直陪伴着奥茨。”

The yeasts—species of Phenolifera, Glaciozyma, Goffeauzyma, and Mrakia—turned up on Ötzi’s skin, in his stomach, and in water sampled from inside his body. Sarhan and his colleagues cultured live yeast from the samples, but their shotgun metagenomics results also revealed a bunch of short fragments of DNA, most bearing the kind of damage that happens when DNA molecules break down over time. 这些酵母——包括 Phenolifera、Glaciozyma、Goffeauzyma 和 Mrakia 等属——出现在奥茨的皮肤上、胃里以及从他体内采集的水样中。Sarhan 和他的同事们从样本中培养出了活酵母，但他们的鸟枪法宏基因组测序结果也揭示了大量短 DNA 片段，其中大多数带有 DNA 分子随时间推移而分解时产生的损伤特征。

That’s a hallmark of ancient DNA, which meant that the yeasts had most likely been living on and in Ötzi’s body since shortly after he died. And when Sarhan and his colleagues compared samples taken in 2010 to those taken in 2019, they saw longer fragments and less damage, on average—in other words, there was more recent DNA in the mix, which suggested the yeasts were slowly but persistently growing. 这是古 DNA 的标志，意味着这些酵母很可能自奥茨去世后不久就一直生活在他的体表和体内。当研究人员将 2010 年采集的样本与 2019 年的样本进行对比时，他们发现平均而言，后者的片段更长、损伤更少——换句话说，样本中包含了更多近期的 DNA，这表明这些酵母正在缓慢但持续地生长。

From there, the yeasts probably lay dormant in between brief thawing sessions, when they proliferated in transient patches of meltwater or moist tissue. And the yeasts may have actually gotten some help from modern efforts to preserve Ötzi’s remains. Three out of the four species can break down phenol, an antifungal compound that conservators used to treat the mummy in 1991. The treatment would have given those particular species an evolutionary edge over others. 此后，这些酵母可能在短暂的解冻期之间处于休眠状态，并在融水或潮湿组织的短暂间隙中增殖。此外，这些酵母可能还从现代保护奥茨遗体的措施中获得了“帮助”。四种酵母中的三种能够分解苯酚，而苯酚正是 1991 年文物保护人员用于处理木乃伊的抗真菌化合物。这种处理方式反而让这些特定的物种在进化上获得了超越其他微生物的优势。