Sequencing the Sea Sulphur Cycle

想象一下这个。一种非常简单的分子，它迷住了遥远海洋中的海鸟，它让小虾在吃午饭时兴奋地翻滚，这导致了遥远的海洋上形成了滚滚的云彩。而且，似乎这还不够，每次你在海边散步时，那种强烈的、令人回味的气味并不是来自你父母告诉你的臭氧，也不是来自《宋飞正传》(Seinfeld)中的卡尔文·克莱恩(Calvin Klein)海洋除臭剂(听；http://podcast.sciam.com/daily/sa_d_podcast_070209.mp3)，，而是这种神奇的小物质，一种名为二甲基硫化物的气体)。这种非凡的化合物不太可能从另一种名为二甲基硫代丙酸酯(简称DMSP)的分子开始，它被大量的海洋浮游生物和海藻用作抗应激保护剂。当这些植物死亡时，它们释放DMSP，然后细菌将其附着，细菌将其分解，利用其中的一部分来满足它们对碳和硫的食物需求。在世界范围内，这以惊人的规模发生，每年有超过4亿吨的DMSP因细菌作用而转移。分解过程的一个产物是神奇的DMS，其中一些被释放到空气中，造成海边特有的气味等。值得注意的是，一些海洋海鸟，如海燕和剪毛鸟，感觉到DMS是食物供应的标志，并在数英里外找到它的家。而且，在不同的尺度上，微小但数量巨大的类似虾的生物，称为桡足类动物，也可以使用DMS来指示附近的食物供应。然而，更重要的是，DMS在大气中被进一步修饰为硫酸盐气溶胶，它充当成核剂，在海洋上空形成云层，就像人们从一粒种子开始在水晶花园中生长晶体一样(某种程度上)。这对全球气候有重大影响，甚至被圣人詹姆斯·洛夫洛克用来支持他的“盖亚假说”。尽管DMS的生产和随后的转化非常重要，但在许多方面，我们对这些过程是如何发生的知之甚少，至少在分子水平上是这样。然而，申请人最近的工作至少揭开了制造DMS并将其转化为其他含硫化合物的一些步骤。然而，非常令人惊讶的是，这项工作也表明，不同种类的海洋细菌可以通过几种不同的方式进行这些反应。因此，我们现在希望了解这些耐人寻味的重要细菌的全部基因组成，以便我们能够揭开它们非凡的新陈代谢灵活性背后的原因。通过获得它们的全部基因组序列，我们将拥有大量的资源来帮助我们和海洋微生物界的其他人更好地了解DMS气体的形成以及生化和环境命运在局部和全球层面上正在发生的事情。

Picture this. A molecule, quite a simple one, which charms the sea birds in distant seas, which makes tiny shrimps tumble in excitement at getting their lunch and, which causes the billowing clouds to form over the far-flung oceans. And, as if that were not enough, every time you stroll by the seaside, that tangy, evocative aroma is due not to the ozone your parents told you about, or the Calvin Klein 'Ocean' deodorant in 'Seinfeld' (listen to; http://podcast.sciam.com/daily/sa_d_podcast_070209.mp3), but to this marvellous little substance, a gas called DIMETHYL SULPHIDE. The rather unlikely starting point for this remarkable compound is another molecule, called Dimethylsulphiopropionate (DMSP for short) which is used by huge numbers of marine plankton and seaweeds as an anti-stress protectant. When these plants die, they release the DMSP and this is then latched onto by bacteria, which break it down, using part of it for their carbon and sulphur food requirements. Worldwide, this occurs at a prodigious scale, with more than 400 million tonnes of DMSP being shifted by bacterial action every year. One product of the breakdown process is the magical DMS, some of which is released into the air, causing, among other things, the characteristic smell of the seaside. Remarkably, some ocean seabirds, such as petrels and shearwaters, sense the DMS as a marker for food supplies and home in on it from miles away. And, on a different scale, tiny, but hugely abundant shrimp-like creatures called copepods can also use DMS to indicate nearby food supplies. More important, though, DMS is further modified in the atmosphere, to sulfate aerosols, which act as nucleating agents to form clouds over the oceans, in the same way (sort of) as one gets crystals to grow in a crystal garden by starting off with a 'seed'. This has major effects on global climate and was even used by that sage, James Lovelock, as a plank to underpin his 'Gaia Hypothesis'. Although the production and subsequent conversions of DMS are hugely important, in many ways, we know very little about how these processes occur, at least at molecular levels. However, recent work by the applicants has unravelled at least some of the steps by which DMS is made and by which it is then transformed into other sulphurous compounds. Very suprisingly, though, that work also showed that there are several different ways in which different species of marine bacteria can undertake these reactions. So, we now wish to know the entire genetic makeup of these intriguing, and important bacteria so that we can unravel just what lies behind their remarkable metabolic flexibility. By having the entire sequences of their genomes, we will have a great set of resources to help us, and others in the marine microbiology world, to understand far better what is going on, at a local and a global level in the formation and biochemical and environmental fate of the DMS gas.