Biochemical and genetic diversity of a critical step in the sulphur cycle - molecular studies of bacterial dimethyl sulphide production

硫循环关键步骤的生化和遗传多样性——细菌二甲硫醚生产的分子研究

基本信息

批准号：
BB/H002642/1
负责人：
Andrew Johnston
金额：
$ 45.73万
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=BB%2FH002642%2F1
关键词：
Biochemical genetic diversity critical step

项目摘要

The gas dimethyl sulphide (DMS for short) does strange things to animals. Tiny shrimp-like crustaceans, some seabirds and even harbour seals get excited by it, since its aroma is a sign of nearby food. And, for the general populace, it is a much-loved memento of days by the beach, being part of the evocative smell of the seaside. But DMS is much more important than that. It represents the major route for transfer of sulphur from the oceans to land and, as such, is a critical part of the natural sulphur cycle, in which living organisms transfer sulphur from one form to another. You may not know it, but many of the molecules in your body contain sulphur and without it we cannot survive. DMS is also important for our environment because when it gets into the air, it is oxidised to form other compounds that act as 'seeds' for cloud formation over the oceans, just as flecks of dust set off crystallisation in crystal gardens. This may affect our climate, by reducing the amounts of light that reaches Earth's surface, perhaps even causing 'global diming'. Furthermore, its oxidation contributes significantly to the phenomenon of acid rain. DMS is made in huge amounts in the oceans - around 300 million tons each year. It is generated by microbes that use another molecule, with a ridiculously long name - dimethylsulphoniopropionate, (DMSP) - as a food source. This DMSP is made by seaweeds and the masses of plankton in the oceans, helping them to survive the stresses of life at sea. When they die, the DMSP is liberated, and is then eaten by some bacteria and fungi, and some of these produce the DMS as a by-product. Other bacteria are more genteel - they devour DMSP in a very different way, which does not produce this microbial sulphurous burp. Given the importance of DMS, it is quite astonishing that today we know so little about genetic basis of its prodution. However, scientists at the University of East Anglia have recently made an important breakthrough by identifying the bacterial genes that are involved in making the DMS. In doing this, they have uncovered at least three completely different ways in which bacteria can make this gas. Not only that, but in the natural environment, these genes can be transferred among very different marine bacteria. Even more remarkably, they were transferred from some bacteria to completely different life forms, such as fungi. And, some of these enzymes, and the organisms that contain them, are of types that had never been suspected of being involved in this important process. Other researchers, at the University of Georgia, have done related work on the genes that are important for the pathway that does not make DMS. Using that information, and their own findings, the UEA group have found one marine bacterium - called Roseovarius nubinhibens - which is a real glutton for DMSP. It has two, possibly three, different ways to make DMS and, as if that were not enough, it can also break down DMSP by the other pathway that does not make DMS. The UEA group now wants to look at the properties of the enzymes that make DMS in this species and to see how a single bacterium decides which of its different pathways it should use under different circumstances - the concentration of the DMSP that is available, the acidity of the medium, the cell density and so on. By learning about these features on these newly discovered systems, we will be much better placed to understand how and why bacteria choose to break down the DMSP in one way, rather than another, and why some make lots of the important gas, but others only make a little. This knowledge will provide great new insights into the natural cycling of one of the most important elements for life on earth.

气体二甲基硫化物（简称DMS）对动物造成了奇怪的事情。小虾状的甲壳类动物，一些海鸟甚至港口海豹会对它感到兴奋，因为它的香气是附近食物的标志。而且，对于普通民众来说，这是海滩上备受喜爱的日子，是海边令人回味的气味的一部分。但是DMS比这重要得多。它代表了从海洋转移到陆地的主要途径，因此是天然硫循环的关键部分，其中活性生物体将硫从一种形式转移到另一种形式。您可能不知道，但是体内的许多分子都含有硫，没有它，我们将无法生存。 DMS对我们的环境也很重要，因为当它进入空气时，它被氧化以形成其他化合物，这些化合物是海洋上云形成的“种子”，就像尘埃落体在水晶花园中散发出结晶一样。这可能会通过减少到达地球表面的光量，甚至导致“全球昏迷”的光线来影响我们的气候。此外，其氧化对酸雨的现象显着促进。 DMS在海洋中大量制造 - 每年约3亿吨。它是由使用另一个分子的微生物产生的，其名称荒谬 - 二甲基磺胺丙酸（DMSP）作为食物来源。该DMSP由海藻和海洋中浮游生物的群体制成，帮助他们在海上生活的压力中生存。当它们死亡时，DMSP将被解放，然后被一些细菌和真菌食用，其中一些会产生DMS作为副产品。其他细菌更绅士 - 它们以截然不同的方式吞噬DMSP，这不会产生这种微生物硫磺bur。鉴于DMS的重要性，令人惊讶的是，今天我们对其产量的遗传基础知之甚少。但是，东英吉利大学的科学家最近通过识别涉及制造DMS的细菌基因，取得了重要的突破。通过这样做，他们至少发现了细菌可以使这种气体的三种完全不同的方式。不仅如此，在自然环境中，这些基因可以在非常不同的海洋细菌中转移。更值得注意的是，它们从某些细菌转移到了完全不同的生命形式，例如真菌。而且，其中一些酶以及包含它们的生物是从未涉嫌参与这一重要过程的类型。佐治亚大学的其他研究人员在对不制造DMS的途径上很重要的基因上进行了相关工作。使用这些信息及其自己的发现，UEA组发现了一种海洋细菌 - 称为Roseovarius nubin usinens-这是DMSP的真正glutton。它有两种制造DM的方法，可能是三种不同的方法，而且似乎还不够，它也可以通过其他不会产生DMS的途径来分解DMSP。现在，UEA组希望查看在该物种中产生DM的酶的性质，并查看单个细菌在不同情况下应使用哪种不同的途径 - 可用的DMSP的浓度，培养基的酸度，细胞密度等。通过在这些新发现的系统上了解这些功能，我们将更好地理解细菌如何以及为什么选择以一种方式分解DMSP，而不是另一种方式，以及为什么有些人会产生很多重要的气体，而另一些则只会产生一点。这些知识将为地球上最重要的元素之一的自然循环提供巨大的新见解。