大开眼界：世界上最大型的真菌

In the late 1980s, researchers discovered the biggest organism on record, a “humongous fungus” on Michigan’s Upper Peninsula that covered 37 hectares, about the same size as the Mall of America in Bloomington, Minnesota.

上世纪80年代末，研究人员在密歇根州上半岛发现了有史以来最大的一种生物，一种“巨型真菌”，占地37公顷，与明尼苏达州布卢明顿的美国购物中心大小相当。

Now, the same team of scientists has found that this Armillaria gallica, which gives rise to honey mushrooms (above), is about four times as big—and twice as old—as they originally thought.

现在，同一组科学家发现，这种能产生蜂蜜蘑菇的蜜环菌(见上图)，比他们原先想象的要大四倍—出现时间也比原来的早两倍。

Like other fungi, Armillaria sprouts tiny threads underground; but unlike most fungi, these threads fuse to form shoelace-size strings that extend great distances to consume dead or weak wood.

像其他真菌一样，蜜环菌在地下萌发细小的菌丝;但与大多数真菌不同的是，这些菌丝会融合成鞋带大小的线，这些线会延伸很远的距离来消耗死的或弱的木材。

To find out how big the massive underground network of fungus really was, the scientists took 245 far-flung string samples and analyzed their genes.

为了弄清巨大的地下真菌网络到底有多大，科学家们采集了245个遥远的线状样本并分析了它们的基因。

Not only did they belong to the same individual fungus, but—based on how fast the underground strands grow—that fungus must be at least 2500 years old, they report in a non–peer-reviewed study posted last week to the bioRxiv preprint server.

这些样本不仅仅属于同一个真菌，而且—根据地下菌丝生长的速度—这个真菌至少有2500年了，他们在上周发表在bioRxiv预印本服务器上的一项非同行评议的研究报告中说。

By sequencing the genomes of 15 evenly distributed samples, the researchers could also see how the honey mushroom’s genome changed over time.

通过对15个分布均匀的样本的基因组进行测序，研究人员还可以看到蜜环菌的基因组是如何随时间发生变化的。

To their surprise, it has a very slow mutation rate, with just 163 genetic changes among the genome’s 100 million bases.

令他们惊讶的是，它的突变率非常低，在基因组的1亿个碱基中只有163个基因发生了变化。

Mutation rates often reflect how quickly an organism can evolve—and this fungus, it seems, doesn’t evolve very fast.

突变率通常反映了生物体进化的快慢，而这种真菌似乎进化得并不快。

The researchers aren’t sure how the mutations rate is kept in check, through a well-developed DNA mechanism or simply being underground and out of sunlight may do the trick.

研究人员不确定突变率是如何被控制的，是通过一种发育良好的DNA机制或者仅仅是位于地下和没有阳光的地方可能会起到作用。

But even with its new size estimate, the Michigan fungus has already been eclipsed by a different Armillaria in Oregon, discovered in 1998.

但是，尽管有了新的估计，密歇根真菌已经被俄勒冈州1998年发现的另一种蜜环菌盖过了。

That one, now the largest organism in the world, may be more than 8000 years old and covers more than 770 hectares.

这是目前世界上最大的生物体，可能已有超过8000年的历史，覆盖面积超过770公顷。

对于这种规模惊人的真菌朋友们有什么看法呢？欢迎给amber留言哦！

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