Linking crenarchaeal activity to global nitrogen cycling in soil

微生物是环境中营养物质周转和转化的关键角色，包括碳和氮。然而，由于我们无法在实验室中培养绝大多数微生物，我们对这些微生物中介过程的理解严重受阻。最近分子技术的应用绕过了这些限制，因为它们绕过了实验室培养的需要，而且它们使我们能够研究“未培养的大多数”，从而彻底改变了我们对微生物多样性的看法。已发现的许多微生物群在实验室培养中没有代表性，因此没有已知的生态系统功能，但在自然环境中丰富。一个重要的例子是中温古生菌，它约占陆地和海洋环境中所有原核生物的6%。分子技术最近预测，弧菌可能在环境中的氨氧化过程中发挥核心作用，这是全球氮循环的关键步骤，此后在实验室中分离出了一株能氧化氨气的弧菌。由于隐古菌是一种比以前描述的氨氧化细菌更丰富的细菌，它们可能代表着生物圈中最重要的氨氧化生物。这项研究计划旨在量化它们在土壤氨氧化中的作用，比较环境因素对它们活性的影响，并确定它们是否具有明显的生态生理特征和生态学。

Microbes are key players in the turnover and transformation of nutrients, including carbon and nitrogen, in the environment. However, our understanding of these microbially mediated processes is severely hampered by our inability to culture the vast majority of microbes in the laboratory. The recent application of molecular techniques has circumvented these limitations, because they bypass the need for laboratory cultivation, and they have revolutionised our view of microbial diversity by enabling us to examine the 'uncultured majority'. Many groups of microbes have been discovered which have no representative in laboratory culture, and therefore no known ecosystem function, but which are abundant in natural environments. An important example is the mesophilic crenarchaea, which constitute approximately 6% of all prokaryotes in terrestrial and marine environments. Molecular techniques recently predicted that crenarchaea may have a central role in the oxidation of ammonia in the environment, a key step in the global nitrogen cycle, and an ammonia oxidising crenarchaea has since been isolated in the laboratory. As crenarchaea are a much more abundant than previously characterised ammonia-oxidising bacteria, they may represent the most important ammonia-oxidising organisms in the biosphere. This research proposal aims to quantify their role in ammonia oxidation in soil, to compare the impact of environmental factors on their activity and that of 'traditional' ammonia-oxidising organisms and to determine whether they possess distinct ecophysiological characteristics and ecology.