The evolutionary ecology of interspecific microbial public-goods

矿山废物是世界范围内的一个主要问题，对人类健康和环境产生有害影响。迫切需要制定长期可持续的修复战略。微生物在地球化学过程中发挥着重要作用，它们巨大的代谢多样性可能有助于矿山退化土壤的清理。微生物群落的解毒不仅取决于个体行为，而且取决于不同物种的集体作用。然而，我们对不同的微生物物种如何相互作用来解毒污染土壤中的金属的知识是有限的。我的首要目标是最大限度地发挥微生物的协同作用，为环境解毒，更一般地说，利用进化生态学理论来解决“现实世界”的问题。合作在细菌中很常见，并且在个别物种中有充分的记录，其中一些菌株产生昂贵的化合物，供邻近细胞使用（即公共产品）。我们对微生物公共产品的大部分理解来自于物种内部的相互作用，然而公共产品往往同时有益于其他物种。关键的例子包括抗生素和环境污染物的细胞外分解。因此，合作对人类健康、农业和生态系统功能具有深远的影响。然而，我们目前对推动社区公共产品生产演变和数量的生态约束知之甚少。物种内合作的主要驱动因素是：(1)空间结构，导致主要的局部互动；(2)资源供应，降低边际成本；(3)对多种公共产品的需求，为劳动分工提供了机会。这些变量对整个社区公共产品的影响可能不同于它们对特定内部公共产品的影响，因此需要进行新的理论和实验研究。我将发展新的理论，以确定关键变量如何同时影响物种内部和物种之间的合作。然后，我将在合成微生物群落中测试理论预测，使用实证结果来完善理论。我将把重点放在一个普遍存在的社会特征上——金属解毒的铁载体的产生。铁载体最为人所知的可能是它们作为铁载体的功能，但这些细胞外分子也可以与有毒金属结合，阻止它们吸收和杀死细菌细胞。这为物种之间的合作提供了可能，但也为物种之间的开发提供了可能，在这种情况下，物种使用其他物种的铁载体而不支付公平的份额。这些受控实验使我能够梳理生态和进化过程，并确定支持铁载体生产变化的分子机制。然后，我将把这些知识应用到自然环境的修复中。在我的研究计划的第二阶段，我将在第一阶段的结果的基础上，增加我们对微生物铁载体在驱动植物-微生物相互作用中的作用的理解。越来越多的证据表明，微生物与植物之间的反馈无处不在，是它们共同发挥作用的关键决定因素。例如，植物和微生物产生影响彼此行为的信号，通常是互利的。然而，我们对这些相互作用是如何受到相互作用的微生物群落中的合作和冲突的影响知之甚少。我将首先测试铁载体的生产是否由于植物根系资源供应和结构的增加而增加，以及解毒微生物之间基于铁载体的合作如何改变植物-微生物的反馈，使用合成和天然土壤群落。

Mine waste is a major problem worldwide, having detrimental effects on human health as well as the environment. There is a pressing need to develop long-term sustainable remediation strategies. Microbes play an important role in geochemical processes and their vast metabolic diversity may aid in the clean up of mine-degraded soils. Detoxification in microbial communities not only depends on individual behaviour, but on the collective action of different species. However, our knowledge of how different microbial species interact with one another to detoxify metals in polluted soils is limited. My overarching aim is to maximise microbial synergism in their efforts to detoxify environments and, more generally, to use evolutionary ecology theory to solve 'real world' problems.Cooperation is common in bacteria, and has been well documented within individual species, where some strains produce costly compounds that are used by neighbouring cells (i.e. public-goods). Most of our understanding of microbial public-goods comes from work on within-species interactions, yet public-goods often simultaneously benefit other species. Key examples include the extracellular break down of antibiotics and environmental pollutants. Cooperation therefore has far-reaching consequences for human health, agriculture and ecosystem functioning. However, we currently have little understanding of the ecological constraints driving the evolution and quantity of community-wide public-goods production. Key drivers of within-species cooperation are: (1) spatial structure, resulting in predominantly localised interactions, (2) resource supply, which reduces marginal costs and (3) the need for multiple public goods, which provides opportunities for division of labour. These variables are likely to affect community-wide public goods differently to how they affect intra-specific public goods, requiring the need for novel theoretical and experimental studies.I will develop novel theory to identify how key variables simultaneously affect cooperation within and between species. I will then test the theoretical predications in synthetic microbial communities, using the empirical results to refine theory. I will focus in on a ubiquitous social trait - the production of metal-detoxifying siderophores. Siderophores are perhaps best known for their function as iron-carriers, but these extracellular molecules can also bind to toxic metals and prevent them from being taking up and killing bacterial cells. This opens up the possibility of between-species cooperation but also exploitation, where species use other species' siderophores without paying their fair share. These controlled experiments allow me to tease apart ecological and evolutionary processes, and identify the molecular mechanisms underpinning changes in siderophore production. I will then apply this knowledge to the remediation of natural environments. During the second phase of my research program, I will build on my results from phase one to increase our understanding of the role of microbial siderophores in driving plant-microbe interactions. Evidence is mounting that microbe-plant feedbacks are ubiquitous and a crucial determinant of their combined functioning. For example, plants and microbes produce signals that affect each other's behaviour, often to mutual benefit. However, we have little understanding of how these interactions are affected by cooperation and conflict within the interacting microbial communities. I will first test whether siderophore production is enhanced as a result of increased resource supply and structure in the plant root system and how siderophore-based cooperation between detoxifying microbes alters plant-microbe feedbacks, using both synthetic and natural soil communities.