Drought represents a significant stress to microorganisms and is known to reduce microbial activity and organic matter decomposition in Mediterranean ecosystems. However, we lack a detailed understanding of the drought stress response of microbial decomposers. Here we present metatranscriptomic and metabolomic data on the physiological response of in situ microbial communities on plant litter to long-term drought in Californian grass and shrub ecosystems. We hypothesised that drought causes greater microbial allocation to stress tolerance relative to growth pathways. In grass litter, communities from the decade-long ambient and reduced precipitation treatments had distinct taxonomic and functional profiles. The most discernable physiological signatures of drought were production or uptake of compatible solutes to maintain cellular osmotic balance, and synthesis of capsular and extracellular polymeric substances as a mechanism to retain water. The results show a clear functional response to drought in grass litter communities with greater allocation to survival relative to growth that could affect decomposition under drought. In contrast, communities on chemically more diverse and complex shrub litter had smaller physiological differences in response to long-term drought but higher investment in resource acquisition traits across precipitation treatments, suggesting that the functional response to drought is constrained by substrate quality. Our findings suggest, for the first time in a field setting, a trade off between microbial drought stress tolerance, resource acquisition and growth traits in plant litter microbial communities.

中文翻译：

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干旱和植物凋落物化学改变了微生物基因的表达和代谢物的产生。

干旱对微生物来说是一种重大压力，并且已知会降低地中海生态系统中的微生物活动和有机物分解。然而，我们缺乏对微生物分解者的干旱胁迫响应的详细了解。在这里，我们提供了关于植物凋落物上原位微生物群落对加利福尼亚草和灌木生态系统中长期干旱的生理反应的元转录组学和代谢组学数据。我们假设干旱导致相对于生长途径更大的微生物分配到胁迫耐受性。在草屑中，来自长达十年的环境和减少降水处理的群落具有不同的分类和功能特征。干旱最明显的生理特征是产生或吸收相容溶质以维持细胞渗透平衡，合成荚膜和细胞外聚合物作为保水机制。结果表明，草屑群落对干旱有明显的功能反应，相对于生长而言，生存分配更大，这可能会影响干旱下的分解。相比之下，化学上更多样化和复杂的灌木凋落物上的群落对长期干旱的生理差异较小，但在降水处理中对资源获取性状的投资较高，这表明对干旱的功能响应受到基质质量的限制。我们的研究结果首次在野外环境中表明，植物凋落物微生物群落中微生物干旱胁迫耐受性、资源获取和生长特性之间的权衡。