Geomicrobial response to environmental stress-functional implications of identifying thresholds in anthropogenic gradients

农业用地和城市对陆地-淡水界面的压力可能导致对生物群的压力增加，水质恶化，并可能成为生态系统健康的障碍。长期以来的生态系统评估方法是使用生物完整性（BI）措施，将退化环境的生物属性与更理想的、受影响最小的环境的生物属性进行对比。然而，人类活动产生了各种各样的物质，对生物群、盐、营养物、碳氢化合物、金属和异种生物造成压力。一个关键的知识缺口是确定BI诊断沉积物和水中这些物质的关键微生物介导转化的措施，并确定这些过程是否可以改善压力。沉积物/水界面在生物地球化学循环（如P、N、S、C、Fe和Si）和水质中起重要作用。虽然这一过渡带拥有大量的微生物类群，但它们的主要功能特征和对日益增加的环境压力（如人为压力、极端环境）的适应能力在很大程度上是未知的。例如，富营养化涉及磷和氮沉积物动力学的研究集中在与金属氧化物及其氧化还原转化（如固氮、矿化（腐烂）、硝化和反硝化）相关的吸附/解吸机制上。然而，这些措施可以是系统特定的，因为基本的微生物成分是建模和概念表征的黑箱。我们结合地球化学方法了解微生物功能表达的方法表明，在细菌存在的情况下，微生物群落对氧化还原波动和矿物溶解的反应之间存在明确的联系，这可以导致金属和营养物质释放的特定途径，并解释细菌如何从这种电子交换代谢中受益。在实验室和实地项目中使用微生物和分析技术，这个假设驱动的研究项目将扩大我们对水生淡水沉积物中细菌对人为压力的反应的理解。我们将确定细菌在沉积物水界面中的机制和功能作用，以转化表征压力生境类别的关键物质。研究结果将在一个新的组学数据库中共享，并用于完善受胁迫影响生态系统的生物地球化学循环模型，提高对微生物异位功能的理解。通过农业、工业、人力和旅游业，维持可持续的淡水资源对加拿大社会经济的可持续发展至关重要。该计划将记录细菌在控制自然淡水生态系统中受人为压力的金属和营养动态方面所起的关键作用。通过确定基因表达的关键生物标志物，我们将推进基于工具的开放阵列在陆地和水生生态系统中污染物评估中的应用。

Agricultural land and urban pressures on the terrestrial-freshwater interface can lead to increased stress on biota, poor water quality and can be an impediment to ecosystem health. A long-standing approach to ecosystem assessment uses biological integrity (BI) measures contrasting biological attributes of degraded environments to those of more desirable, minimally impacted ones. However, anthropogenic activity produces diverse materials that stress biota, salts, nutrients, hydrocarbons, metals, and xenobiotics. A critical knowledge gap is to identify measures of BI diagnostic of the key microbially-mediated transformations of those materials in sediment and water and determining whether how these processes can ameliorate the stress. The sediment/water interface plays an important role in biogeochemical cycles (e.g., P, N, S, C, Fe and Si) and water quality. Although this ecotone harbors a vast array of microbial taxa, their dominant functional characteristics and resilience to increasing environmental stress e.g., anthropogenic pressures, environmental extremes are largely unknown. For example, studies of eutrophication involving P and N sediment dynamics have focused on adsorption/desorption mechanisms associated with metal oxides and their redox transformations (e.g., nitrogen fixation, mineralization (decay), nitrification and denitrification). However, these measures can be system specific as the essential microbial component is a black box in modelling and conceptual characterization. Our approach to understanding microbial functional expression coupled with geochemical methods show clear connections between microbial community response to redox fluctuations and mineral dissolution in the presence of bacteria, which can lead to specific pathways of metal and nutrient release and explain how the bacteria benefit from this electron exchange metabolism. Using microbial and analytic techniques in laboratory and field-based programs, this hypothesis driven research program will expand our understanding of bacterial response to anthropogenic pressure in aquatic freshwater sediments. We will identify the mechanistic and functional roles of bacteria at the sediment water interface in transforming key materials of concern that characterize classes of stressed habitats. Results will be shared in a new omics database and used to refine models of biogeochemical cycling in stress impacted ecosystems and improve understanding of microbial heterotopic function. Maintaining sustainable freshwater resources is essential to Canada's socio-economic sustainability through agriculture, industry, people, and tourism. This program will document the critical role that bacteria play in controlling metal and nutrient dynamics in natural freshwater ecosystems subject to anthropogenic stress. By identifying key biomarkers of gene expression, we will advance the application of tool based open arrays for assessing contaminants in terrestrial and aquatic ecosystems.