Structure and function of replicate natural bacterial communities

我们依靠细菌提供的服务来消化我们的食物，分解污染物，并回收对维持自然生态系统至关重要的营养物质。尽管它们很重要，但我们才刚刚开始了解细菌群落是如何运作的。这是有充分理由的。微生物世界可能是最复杂和动态的生物生态系统，因此实验仍处于起步阶段。拟议的研究将探讨描述控制生物多样性（如物种数量）和细菌群落组成（即物种身份）的因素及其对生态系统功能的影响的基本问题。采用的方法是采用一个相对简单但自然的生态系统，易于复制。这样一个系统是由充满水的树洞提供的，这是“自然的微观世界”，我过去曾成功地利用它来揭示一些基本模式。特别是，之前的研究表明，更大的树洞含有更多不同的细菌群落。此外，当从树洞中分离细菌并在实验室中重建群落时，更多样化的群落也具有更高水平的生态系统功能（以细菌群落的总呼吸量来衡量）。目前的建议是从这些令人兴奋的结果中得出的，通过进行一系列的实地实验，试图发现这些模式背后的机制。例如，一种可能的机制是，较大的树洞含有更多不同的细菌群落，因为细菌细胞在较大的树洞中的定植速度更快。拟议研究的主要目标是评估改变定殖率改变细菌群落最终状态的程度。这是通过明确地操纵野外的定植率来实现的。我还建议调查由此产生的不同群落在生态系统功能水平上是否也存在差异。这样一个实验的结果通过展示定植动态如何影响细菌群落，对微生物生态学具有深远的影响，这一发现将成为我们理解微生物群落如何运作的核心。

We rely on the services that bacteria provide to digest our food, to breakdown pollutants, and to recycle the nutrients that are essential for maintaining natural ecosystems. Despite their importance, we are only beginning to understand how communities of bacteria operate. There is good reason why this is the case. The microbial world is perhaps the most complex and dynamic biological ecosystem, so experiments remain in their infancy. The proposed research will investigate fundamental questions in describing the factors that control the biodiversity (e.g. the number of species) and composition (i.e. the identity of the species) of bacterial communities and the consequences for ecosystem functioning. The approach that is used is to take a relatively simple but natural ecosystem that is easy to replicate. Such a system is provided by water-filled treeholes, which are 'natural microcosms' that I have used successfully in the past to uncover some fundamental patterns. In particular, this previous work has shown that larger treeholes contain more diverse bacterial communities. In addition, when bacteria are isolated from the treeholes and the communities are re-constructed in the laboratory, more diverse communities also have higher levels of ecosystem functioning (measured as the total respiration of the bacterial community). The current proposal follows from these exciting results by conducting a series of field experiments that attempt to discover the mechanisms that underlie the patterns. For example, one possible mechanism is that larger treeholes contain more diverse bacterial communities because colonisation by bacterial cells is more rapid into larger treeholes. The principle goal of the proposed research is to assess the degree to which altering the colonisation rate alters the final state of the bacterial community. This is done by explicitly manipulating colonisation rate in the field. I also propose to investigate whether the different communities that are thus created also differ in their level of ecosystem functioning. The results of such an experiment has far-reaching implications for microbial ecology by demonstrating how colonisation dynamics influence bacterial communities, a finding that would lie at the heart of our understanding of how microbial communities operate.