Making and breaking DMS by salt marsh microbes - populations and pathways, revealed by stable isotope probing and molecular techniques

盐沼微生物制造和破坏 DMS - 通过稳定同位素探测和分子技术揭示的种群和途径

基本信息

批准号：
NE/H008586/1
负责人：
Andrew Johnston
金额：
$ 19.04万
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：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH008586%2F1
关键词：
Making breaking DMS salt marsh

项目摘要

There is an evocative gas, called dimethyl sulfide - DMS for short - which most of us have smelled, since it is a component of the smell of the seaside. But it is far more important than that. Around 300 million tons are made each year by marine microbes, around 10% of which escapes into the atmosphere. Not only does this bring back memories of days by the sea, but DMS is chemically modified in the air to compounds that cause clouds to form over the oceans, affecting weather and climate. And, when it rains, these compounds come back to earth in a major step in the global circulation of the essential element sulfur. And one more thing. Even in tiny amounts, DMS attracts different marine animals - fish, penguins and tiny crustaceans all swim, fly or paddle towards it as fast as they can. The reason is that they know that where there is DMS there is food. This is because DMS is a by-product of biochemical processes that occur when different microbes devour another sulfur-containing molecule, with a ridiculously long name - dimethylsulfoniopropionate. This DMSP is made in prodigious amounts by tiny plankton organisms in the oceans, by seaweeds and by a very few land plants that live by the sea. At UEA, we discovered how microbes make the DMS and in Warwick, the ways in which other marine microbes can further transform this gas are studied. We use molecular biology, gene cloning and DNA sequencing to identify the genes in a whole range of microbes that let them undertake these reactions. For both processes, we found that some very unexpected organisms can make or can break down DMS and that they can do this in completely different and surprising ways. Most of these studies are on purified strains that we grow in the lab. This lets us identify the genes and their individual functions, but it does not tell us which are the most important pathways and which of the microbes are the key players in natural environments. This is because the great majority of bacteria that live 'out here' in the natural world have never been cultured. Luckily, some very recent techniques let us study such 'difficult' microbes. One neat trick, invented by Professor Murrell, is to feed natural populations of microbes with a version of the substrate that is chemically identical to the normal one but which is, literally, heavier. So, in our case, we will use forms of DMS and DMSP in which the carbon atoms have an atomic weight of 13, not the more conventional 12. When a microbe digests such a heavy molecule, the heavy carbon is incorporated into its molecules, including DNA. By purifying this heavy DNA from the light form and by looking for signature sequences in the genes, the microorganisms and fungi that used the DMS or the DMSP can be identified and the mechanisms by which they do so can be inferred. We will do these experiments on mud from the salt marshes of North Norfolk. These are home to the grass Spartina, one of the few land plants that makes DMSP. This plant is also important because it is has been spread by human hand across the world and is now a serious pest on many coasts all over the world, killing off many native species. Not surprisingly, there is a lot of DMSP around Spartina roots, which teem with bacteria and fungi that consume or make DMS. We will therefore conduct a census of these microbes, some of which may be new to science. Our findings should relate to other hotspots for DMS and DMSP, such as corals and the massive blooms of plankton in the oceans. Although very small, the sheer numbers of microbes mean that they affect our environment more than most of us realise. Given the environmental consequences of the DMS gas, it is important to know which types of bacteria and fungi that affect its production and destruction and which of the various potential pathways are involved. This may help us model how environmental changes such as climate change alter the balance of these processes.

有一种令人回味的气体，称为二甲硫醚（简称 DMS），我们大多数人都闻过，因为它是海边气味的组成部分。但它远比这重要。海洋微生物每年生产约 3 亿吨，其中约 10% 逃逸到大气中。这不仅让人回想起在海边度过的日子，而且 DMS 在空气中经过化学修饰，形成化合物，导致海洋上空形成云，影响天气和气候。而且，下雨时，这些化合物会返回地球，这是必需元素硫的全球循环的重要一步。还有一件事。即使数量很少，DMS 也会吸引不同的海洋动物——鱼类、企鹅和小型甲壳类动物都会以最快的速度向它游、飞或划。原因是他们知道哪里有 DMS 哪里就有食物。这是因为 DMS 是不同微生物吞噬另一种含硫分子时发生的生化过程的副产品，它的名字长得可笑——二甲基磺酰基丙酸酯。这种 DMSP 是由海洋中的微小浮游生物、海藻和极少数生活在海边的陆地植物产生的。在东英吉利大学，我们发现了微生物如何产生 DMS；在沃里克大学，我们研究了其他海洋微生物进一步转化这种气体的方式。我们利用分子生物学、基因克隆和 DNA 测序来识别各种微生物中能够进行这些反应的基因。对于这两个过程，我们发现一些非常意想不到的生物体可以制造或分解 DMS，并且它们可以以完全不同且令人惊讶的方式做到这一点。这些研究大部分都是针对我们在实验室培养的纯化菌株。这让我们能够识别基因及其各自的功能，但它并没有告诉我们哪些是最重要的途径以及哪些微生物是自然环境中的关键参与者。这是因为自然界中生活在“这里”的绝大多数细菌从未被培养过。幸运的是，一些最近的技术让我们能够研究这种“困难”的微生物。穆雷尔教授发明了一个绝妙的技巧，就是用一种化学性质与普通底物相同但实际上更重的底物来喂养自然微生物群体。因此，在我们的例子中，我们将使用 DMS 和 DMSP 的形式，其中碳原子的原子量为 13，而不是更传统的 12。当微生物消化如此重的分子时，重碳会并入其分子中，包括DNA。通过从轻链中纯化重链 DNA 并寻找基因中的特征序列，可以识别使用 DMS 或 DMSP 的微生物和真菌，并推断它们的作用机制。我们将在北诺福克盐沼的泥浆上进行这些实验。这里是大米草的家园，大米草是为数不多的能够制造 DMSP 的陆地植物之一。这种植物也很重要，因为它是由人类手工传播到世界各地的，现在是世界各地许多海岸的严重害虫，杀死了许多本地物种。不足为奇的是，大米草根部周围存在大量 DMSP，其中充满了消耗或制造 DMS 的细菌和真菌。因此，我们将对这些微生物进行普查，其中一些对科学来说可能是新的。我们的发现应该与 DMS 和 DMSP 的其他热点相关，例如珊瑚和海洋中浮游生物的大量繁殖。尽管微生物非常小，但其数量之多意味着它们对我们环境的影响比我们大多数人意识到的要大。考虑到 DMS 气体对环境的影响，了解影响其产生和破坏的细菌和真菌类型以及涉及哪些潜在途径非常重要。这可能有助于我们模拟气候变化等环境变化如何改变这些过程的平衡。