Impact of bacterial biomass on the surface wettability of soil particles under varying moisture conditions

不同湿度条件下细菌生物量对土壤颗粒表面润湿性的影响

• 批准号: 298894107
• 负责人: Dr. Dörte Diehl
• 金额: --
• 依托单位: Universitätsleitung - Präsidium
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/298894107?language=en
• 关键词: Impact; bacterial; biomass; surface; wettability

Particle wettability is an important controlling factor for a multitude of processes in soil, including fluid movement and distribution, transport and adsorption of colloids and organic molecules, as well as biological activity. Low wettability of soil particles (soil water repellency) generally is considered to be attributable to the presence of adsorbed organic compounds derived from fungal hyphae or plant material. Recent research revealed first evidence for a potential role of bacterial biomass in the development of water repellency in soil. However, until now it is unclear to which extent bacterial cells and their fragments contribute to the occurrence and persistence of soil water repellency and whether bacterial adaptation to water and salt stress can possibly explain the frequently observed variation of water repellency in response to wetting and drying events. Our project aims at unraveling these questions in a series of closely interlinked joint experiments by (1) investigating the factors and conditions that contribute to the occurrence of bacterial surface hydrophobicity, (2) analyzing how bacterial surface properties are reflected by the surface properties of cell-mineral associations and soil material, (3) evaluating the biological and physical stability of cell/fragment (necromass)-mineral associations, and (4) testing the potential feedback of soil particle wettability on bacteria and their surface properties. Starting from experiments in artificial systems, pure bacterial cultures will be exposed to different kinds of stress (osmotic or matric stress) and the isolated cells and cell fragments subsequently intermixed with mineral particles. Surface properties of bacterial cells, minerals and their associations will be characterized by combining contact angle measurements and surface free energy calculations with information on surface chemical structure and nanomechanical properties obtained by X-ray photoelectron spectroscopy and atomic force microscopy. Using the combination of these techniques will help to explore the underlying mechanisms of changes in bacterial surface properties and will allow identifying important interaction mechanisms between minerals and bacterial cells as a prerequisite for evaluating the persistence of the observed effects. Analysis of phospholipid fatty acids in soils exposed to different drought levels will provide first information on drought-induced shifts in the soil microbial community and on bacteria which are particularly effective in changing the wetting properties of soil particles. Identification of biomarkers with strong relationship to cell surface properties will potentially allow to estimate cell wettability even in complex systems such as natural soil. Ultimately, the synthesis of data obtained in this project will greatly enhance the mechanistic understanding of processes and controlling factors involved in the microbially-mediated development and dynamics of soil water repellency.

颗粒润湿性是土壤中许多过程的重要控制因素，包括流体的运动和分布、胶体和有机分子的迁移和吸附以及生物活性。土壤颗粒的低润湿性(土壤拒水性)通常被认为是由于真菌菌丝或植物材料中存在被吸附的有机化合物。最近的研究首次揭示了细菌生物量在土壤拒水性发展中的潜在作用。然而，到目前为止，还不清楚细菌细胞及其片段在多大程度上有助于土壤拒水性的发生和持续，也不清楚细菌对水和盐胁迫的适应是否可能解释经常观察到的憎水性随干湿事件的变化。我们的项目旨在通过一系列紧密相连的联合实验来解决这些问题，方法是(1)调查导致细菌表面疏水性发生的因素和条件，(2)分析细菌表面属性如何通过细胞-矿物组合和土壤材料的表面属性来反映，(3)评估细胞/碎片(坏死团)-矿物组合的生物和物理稳定性，以及(4)测试土壤颗粒润湿性对细菌及其表面属性的潜在反馈。从人工系统的实验开始，纯细菌培养物将暴露在不同类型的压力(渗透或基质压力)下，分离的细胞和细胞碎片随后与矿物质颗粒混合。通过将接触角测量和表面自由能计算与X射线光电子能谱和原子力显微镜获得的表面化学结构和纳米机械性能信息相结合，将表征细菌细胞、矿物及其缔合的表面属性。结合使用这些技术将有助于探索细菌表面性质变化的潜在机制，并将允许确定矿物和细菌细胞之间的重要相互作用机制，作为评估观察到的影响的持久性的先决条件。对暴露在不同干旱程度下的土壤中磷脂脂肪酸的分析将提供有关干旱引起的土壤微生物群落变化和细菌的第一批信息，这些细菌在改变土壤颗粒的润湿特性方面特别有效。识别与细胞表面性质密切相关的生物标记物将潜在地估计细胞的润湿性，即使在自然土壤等复杂系统中也是如此。最终，本项目所获得的数据的综合将极大地加强对微生物介导的土壤拒水发育和动态过程和控制因素的机理理解。