雪中充滿了微小的生命

雪中充滿了微小的生命

Frosty the Snowman famously came to life one day with the help of a magical silk hat. As recent research suggests, however, he and other snowmen might already be more "alive" than most people realize — even if they aren't dancing around with broomstick canes. That's because, regardless of how it's sculpted or adorned, snow itself is often surprisingly full of microbial life.

有一天，雪人Frosty在一頂神奇的絲綢帽子的幫助下蘇醒了過來。然而，最近的研究表明，他和其他雪人可能已經(jīng)比大多數(shù)人意識到的更“活躍”了——即使他們沒有拿著掃帚和拐杖跳舞。這是因?yàn)椋瑹o論如何雕刻或裝飾，雪本身往往充滿了令人驚訝的微生物生命。

Photo: ch123/Shutterstock

That includes snow that's been lying on the ground for weeks or months, but freshly fallen snow can teem with tiny creatures, too. Some microbes even play key roles in the formation of snowflakes long before they fall.

這包括已經(jīng)在地上躺了幾周或幾個(gè)月的雪，但是新落下的雪也會有很多小生物。有些微生物甚至在雪花形成過程中起著關(guān)鍵作用。

Although life generally depends on liquid water, a variety of organisms have evolved impressive techniques for surviving in snow and ice. They may wait for seasonal thaws, slow their metabolisms, produce antifreeze proteins or encourage the snow around them to melt. A few have been known to science for a long time, but many have only been discovered in recent years.

雖然生命通常依賴液態(tài)水，但各種各樣的生物體已經(jīng)進(jìn)化出了在冰雪中生存的令人印象深刻的技術(shù)。它們可能會等待季節(jié)性的解凍，減緩新陳代謝，產(chǎn)生防凍蛋白，或者促使周圍的雪融化。一些已經(jīng)為科學(xué)界所知很長一段時(shí)間了，但是許多是最近幾年才被發(fā)現(xiàn)的。

There is "watermelon snow," for example, whose pink or red color was documented centuries ago by Aristotle. It wasn't until the 19th century, though, that scientists realized it was caused by something alive in the snow. We now know it can be caused by a few kinds of algae, including Chlamydomonas nivalis, which is often found in mountains, polar regions and other places where snow lasts all year. The algae themselves are green, but they produce a red pigment as a defense against UV radiation. The pigment also reduces the albedo of snow, helping it melt and support more algae. The algae help other life inhabit snow, too, by serving as prey for creatures like ice worms, nematodes, rotifers and tardigrades.

比如“西瓜雪”，它的粉色或紅色早在幾個(gè)世紀(jì)前就被亞里士多德記錄下來了。然而，直到19世紀(jì)，科學(xué)家們才意識到它是由雪中的某種生物引起的。我們現(xiàn)在知道它可能是由幾種藻類引起的，包括經(jīng)常在山區(qū)、極地和其他終年下雪的地方發(fā)現(xiàn)的nivalis衣藻。藻類本身是綠色的，但它們會產(chǎn)生一種紅色色素來抵御紫外線輻射。這種色素還能降低雪的反照率，幫助雪融化并支持更多的藻類。這些藻類也幫助其他生物棲息在雪中，它們是冰蟲、線蟲、輪蟲和緩步動物的獵物。

Even if snow is pristinely white, it may still host a wealth of microbial life. That's what researchers recently found after looking for microbial DNA in snow samples from Northern Europe and North America. Published earlier this year in the journal Microbial Ecology, their findings reveal a hidden empire of bacteria, fungi and algae in seemingly lifeless snow. "I was just blown away by the biodiversity," co-author Shawn Brown, a professor of biology at the University of Memphis, told New Scientist.

即使雪是原始的白色，它仍然可能有豐富的微生物生命。這是研究人員最近在北歐和北美的雪樣本中尋找微生物DNA后發(fā)現(xiàn)的。今年早些時(shí)候發(fā)表在《微生物生態(tài)學(xué)》雜志上的發(fā)現(xiàn)揭示了一個(gè)隱藏在看似沒有生命的雪地里的細(xì)菌、真菌和藻類帝國。“我被生物多樣性震驚了，”論文的合著者、孟菲斯大學(xué)的生物學(xué)教授肖恩·布朗告訴《新科學(xué)家》雜志。

Snow often carries microbes before it even reaches the ground, and in some cases it may not have formed without them. Like raindrops, snowflakes develop in the sky when water molecules cluster around some kind of nucleus. That could be a particle of dust or soot, but research suggests many snowflakes form around a bacterium of the species Pseudomonas syringae.

雪通常在到達(dá)地面之前就攜帶了微生物，在某些情況下，如果沒有它們，雪可能就不會形成。就像雨滴一樣，當(dāng)水分子聚集在原子核周圍時(shí)，雪花就會在天空中形成。那可能是一粒灰塵或煤煙，但研究表明，許多雪花是在一種名為“丁香假單胞菌”的細(xì)菌周圍形成的。

These bacteria float into the sky as moisture evaporates from foliage and soil, or they can just be whisked into the atmosphere by wind. Their surfaces have proteins that are highly effective at prompting water to freeze, so once they're up in a cloud, water molecules cluster around them, freeze and fall as precipitation. P. syringae is so helpful for snow formation that it's often used to create artificial snow for ski slopes, according to Micropia, a museum in Amsterdam dedicated to microbes.

當(dāng)水分從樹葉和土壤中蒸發(fā)時(shí)，這些細(xì)菌會飄浮到空中，或者它們會被風(fēng)吹到大氣中。它們的表面有一種蛋白質(zhì)，能有效地促使水結(jié)冰，所以一旦它們在云層里，水分子就會聚集在它們周圍，凍結(jié)并沉淀下來。阿姆斯特丹一家專門研究微生物的博物館Micropia稱，紫丁香對雪的形成非常有幫助，經(jīng)常被用來為滑雪場制造人工雪。

There are also algae that live in glaciers and sea ice, as well as other ice-adapted microbes that remain shrouded in mystery or have yet to be discovered. Scientists have found intriguing hints of bacterial life in Antarctica, for example, in surface snow as well as in dark lakes sealed deep below an enormous ice sheet.

也有藻類生活在冰川和海冰中，還有其他適應(yīng)冰的微生物仍然籠罩在神秘之中或尚未被發(fā)現(xiàn)?？茖W(xué)家們在南極洲發(fā)現(xiàn)了有趣的細(xì)菌生命跡象，例如，在表面的雪中，以及深埋在巨大冰原下的黑暗湖泊中。

Many snow and ice microbes may play important ecological roles, but we still have a lot to learn about where they live, what they do and how they work. Unfortunately, some of these cold-adapted microbes may soon see their habitats transformed by human-induced climate change, which is widely melting ice and scrambling snowfall patterns.

許多冰雪微生物可能扮演著重要的生態(tài)角色，但關(guān)于它們生活在哪里、它們做什么以及它們是如何工作的，我們還有很多要了解。不幸的是，一些適應(yīng)寒冷的微生物可能很快就會看到它們的棲息地被人類引起的氣候變化所改變，這是廣泛融化的冰和混亂的降雪模式。

Snow and ice would be beautiful even if they were lifeless, so their support of mysterious microbial communities is yet another reason not only to appreciate the world we've inherited, but also to do what we can to protect it. An extinction crisis increasingly threatens species around the planet, and unlike Frosty, vanishing wildlife can rarely promise to "be back again someday."

即使沒有生命，冰雪也會是美麗的，因此，它們對神秘微生物群落的支持，不僅是我們欣賞這個(gè)世界的另一個(gè)理由，也是我們盡力保護(hù)它的另一個(gè)理由。一場滅絕危機(jī)正日益威脅著地球上的物種，而與霜凍不同的是，正在消失的野生動物很少能保證“有一天會再回來”。