Cloning the smell of the seaside - molecular genetics of dimethyl sulphide production by bacteria

克隆海边的气味——细菌产生二甲硫醚的分子遗传学

• 批准号: BB/E01688X/1
• 负责人: Andrew Johnston
• 金额: $ 42.99万
• 依托单位: University of East Anglia
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FE01688X%2F1
• 关键词: Cloning; smell; seaside; molecular; genetics

We've all been to the seaside and we've all been told by a knowing parent to 'breathe in that ozone', because it's 'good for you'. Well, firstly, it's not ozone and second, it's not terribly good for you. That distinctive aroma is, in fact another gas, called dimethyl sulphide (DMS) and it has been known since 1971 that it is hugely important, with some 30 million tons of it being liberated into the air, world wide, every year. And once in the atmosphere it has other major effects, being the 'seed' that sets off cloud formation over the oceans. Indeed, it has been proposed that the production of this molecule is on such a scale that it has major effects on the world's climate. Yet, despite all this, we have absolutely no idea of how, at a molecular level, this process occurs. This is all the more surprising since we have known for some time that many marine bacteria, some of which are easy to grow in the laboratory, can liberate DMS if supplied with the key precursor molecule, called Dimethylsulphiopropionate - DMSP for short. Not a compound one reads about every day, yet there are over two billion tonnes of it in the world's oceans, seas and seashores. That's the weight, give or take, of another seaside symbol, the Blackpool Tower - 70,000 times over. Amazing. This DMSP molecule is used by the great masses of marine plant life - seaweeds and microscopic plankton - as a buffer, or osmo-protectant, against the saltiness of the sea. When these plants die, some of the DMSP that escapes from them is used as food by some marine bacteria and, when they do so, they convert some of it to the DMS gas in the process. We recently isolated one such DMSP-consuming bacterium from the Norfolk coast and used various molecular techniques to get our hands on some of the genes that are involved. By looking at their sequences, we can guess what the genes might be doing and, so far, it looks as if the mechanisms are very different from those hypothetical ones that had been proposed before. We also saw that very similar genes exist in some other, very unexpected, types of bacteria, such as those that live, symbiotically, on the roots of land plants. So the extent of DMS production by bacteria may be far wider and varied than we had thought. We now hope to get a much deeper understanding on this process, at least in 'our' strain. We want to identify and characterize all the enzymes that are involved and we want to know how the pathway is regulated - we already know that these bacteria are not stupid, since they only switch on their systems for degrading the DMSP if the compound is present in their environment. Once we know what is happening with this Norfolk strain, it should be fairly straightforward to find out if other types of marine bacteria that eat DMSP do so in the same way. So, for the first time, we are close to getting a real insight into the molecular details of this pathway, allowing us to amuse, fascinate and educate our friends the next time we go to Great Yarmouth and somebody asks about the delicate scent of rotting seaweed that drifts up from the golden sands.

我们都去过海边，一位知情的父母告诉我们“呼吸臭氧”，因为它“对你有好处”。嗯，首先，它不是臭氧，其次，它对你来说并不是很好。这种独特的香气实际上是另一种气体，称为二甲硫醚 (DMS)，自 1971 年以来人们就知道它非常重要，全世界每年约有 3000 万吨二甲硫醚被释放到空气中。一旦进入大气层，它就会产生其他重大影响，成为在海洋上空形成云的“种子”。事实上，有人提出，这种分子的生产规模如此之大，以至于对世界气候产生了重大影响。然而，尽管如此，我们完全不知道这个过程在分子水平上是如何发生的。更令人惊讶的是，因为我们早就知道许多海洋细菌（其中一些很容易在实验室中生长）如果提供了关键的前体分子（称为二甲基硫代丙酸酯，简称 DMSP），就可以释放 DMS。没有一种化合物是人们每天都会读到的，但世界海洋和海岸中却有超过 20 亿吨的化合物。这是另一个海滨标志——布莱克浦塔的重量的 70,000 倍。惊人的。这种 DMSP 分子被大量海洋植物（海藻和微型浮游生物）用作缓冲剂或渗透保护剂，以抵御海水的咸味。当这些植物死亡时，一些从它们中逸出的 DMSP 被一些海洋细菌用作食物，当它们这样做时，它们会在此过程中将其中一些转化为 DMS 气体。我们最近从诺福克海岸分离出一种这样的 DMSP 消耗细菌，并使用各种分子技术来获得一些相关基因。通过观察它们的序列，我们可以猜测这些基因可能在做什么，到目前为止，看起来这些机制与之前提出的假设机制非常不同。我们还发现，非常相似的基因存在于其他一些非常出乎意料的细菌类型中，例如那些共生在陆地植物根部的细菌。因此，细菌产生 DMS 的范围可能比我们想象的更广泛、更多样化。我们现在希望能够更深入地了解这个过程，至少是在“我们的”压力下。我们想要识别和表征所有涉及的酶，我们想知道该途径是如何调节的 - 我们已经知道这些细菌并不愚蠢，因为它们只有在化合物存在于 DMSP 中时才会打开其系统来降解 DMSP。他们的环境。一旦我们知道了这种诺福克菌株发生了什么，就可以很容易地找出以 DMSP 为食的其他类型的海洋细菌是否也以同样的方式这样做。因此，我们第一次接近真正了解这一途径的分子细节，这让我们下次去大雅茅斯时，当有人问起腐烂的微妙气味时，我们可以逗乐、着迷并教育我们的朋友从金色的沙滩上飘浮起来的海藻。