SP08: Microbiome and stress

干旱胁迫极大地改变了土壤性质。水分有效性的降低增加了氧有效性和溶质浓度，降低了扩散速率并改变了土壤的物理性质。这种变化会对微生物产生一连串的影响。例如，根分泌物减少会导致异养根际细菌的营养短缺，从而降低它们的代谢活动。这可能会影响植物的营养回报。这些级联如何被植物多样性引起的生态系统稳定性、多功能性或干旱严重程度所改变尚不清楚，这将是拟议研究的一个核心问题。因此，我们将研究抗旱性细菌的多样性、相对丰度和活性如何随着植物多样性和干旱强度的梯度而变化。我们将使用Y-A-S框架将抗旱性状分为与产量提高(Y)、养分获取(A)和胁迫耐受性(S)相关的类别。这包括能够矿化氮和磷（Y-A），产生外多糖（A-S）或渗透保护物质(S)或能够休眠(S)的细菌。我们将解决以下研究问题：1)植物多样性如何改变具有不同耐旱性状的细菌的相对丰度和多样性？2)在何种干旱强度下，抗旱细菌（S策略）优于Y-A策略，这是如何通过植物多样性介导的？3)种子细菌和土壤细菌的耐旱特性有何不同？为了解决这些问题，我们将参加Main实验和DrY实验，分别比较植物多样性对耐旱细菌的长期影响和对不同干旱严重程度的短期响应。此外，我们将进行MockCoMic实验，测试从主实验的种子和根际土壤中分离的耐旱细菌合成联合体对植物减轻干旱胁迫的有效性。我们将测试(1)具有不同耐旱性状的微生物与植物抗旱性和恢复的相关性；(2)细菌是来自根际土壤还是种子是否重要。通过我们的建议，我们将特别有助于研究部门的总体假设，即植物多样性稳定生态系统功能，并且可以根据对干旱的短期反应来预测长期模式。此外，我们将能够将功能电位与贡献微生物群的多样性联系起来。这使我们能够估计生态系统的稳定性是通过(1)具有不同耐旱性状的细菌的增加（多功能性）实现的，例如，覆盖整个Y-A-S三角形，还是(2)具有相同性状的细菌群落的多样化，例如，更多样化的多糖生产者，或者(3)两者兼而有。

Drought stress drastically changes soil properties. The reduced water availability increases oxygen availability and solute concentration, reduces diffusion rates and changes physical soil properties. Such changes induce a cascade of consequences for microorganisms. For example, reduced root exudation causes nutrient shortage for heterotrophic rhizosphere bacteria, which then reduce their metabolic activity. That might affect nutrient return to the plant. How such cascades are altered by plant diversity-induced ecosystem stability, multifunctionality or drought severity is not known and will be a central question of the proposed research. Therefore, we will investigate how drought resistant bacteria change in diversity, relative abundance and activity along plant diversity and drought intensity gradients. We will use the Y-A-S framework to classify drought resistance traits in the categories related to yield improvement (Y), nutrient acquisition (A) and stress tolerance (S). That includes bacteria able to mineralize nitrogen and phosphorus (Y-A), produce exopolsyaccharides (A-S) or osmoprotective substances (S) or those being able to become dormant (S). We will address the following research questions: 1) How does plant diversity alter the relative abundance and diversity of bacteria exhibiting different drought-tolerance traits? 2) At which drought intensity do drought-resistant bacteria (S strategy) prevail over Y-A strategists and how is that mediated by plant diversity? 3) How do drought-tolerance traits of seed and soil-derived bacteria differ? To address these questions, we will participate in the Main Experiment and the DrY Experiment, to compare long-term plant diversity effects on drought-tolerant bacteria and short-term responses to different drought severity, respectively. Additionally, we will perform a MockCoMic Experiment, which tests synthetic consortia of drought-tolerant bacteria, which are isolated from seeds and rhizosphere soils of the Main Experiment, for their effectiveness to reduce drought stress of plants. We will test (1) the relevance of microbes with different drought-tolerance traits for the plant drought resistance and recovery and (2) if it matters whether the bacteria originate from the rhizosphere soil or the seed. With our proposal, we will particularly contribute to the overarching hypothesis of the Research Unit that plant diversity stabilizes ecosystem functioning and that the long-term pattern can be predicted based on short-term responses to drought. In addition, we will be able to link functional potentials to the diversity of contributing microbial groups. This enables us to estimate whether ecosystem stability is achieved by (1) an increase of bacteria with different drought tolerance traits (multifunctionality), for example, covering the whole Y-A-S triangle or (2) by a diversification of bacterial communities with the same trait, for example, more diverse polysaccharide producers or (3) both.