Ecosystem engineers (EEs) are present in every environment and are known to strongly influence ecological processes and thus shape the distribution of species and resources. In this study, we assessed the direct and indirect effect of two EEs (perennial shrubs and ant nests), individually and combined, on the composition and function of arid soil bacterial communities. To that end, topsoil samples were collected in the Negev desert highlands during the dry season from four patch types: (1) barren soil; (2) under shrubs; (3) near ant nests; or (4) near ant nests situated under shrubs. The bacterial community composition and potential functionality were evaluated in the soil samples (14 replicates per patch type) using 16S rRNA gene amplicon sequencing together with physico-chemical measures of the soil. We have found that the EEs affected the community composition differently. Barren patches supported a soil microbiome, dominated by Rubrobacter and Proteobacteria, while in EE patches Deinococcus-Thermus dominated. The presence of the EEs similarly enhanced the abundance of phototrophic, nitrogen cycle, and stress-related genes. In addition, the soil characteristics were altered only when both EEs were combined. Our results suggest that arid landscapes foster unique communities selected by patches created by each EE(s), solo or in combination. Although the communities' composition differs, they support similar potential functions that may have a role in surviving the harsh arid conditions. The combined effect of the EEs on soil microbial communities is a good example of the hard-to-predict non-additive features of arid ecosystems that merit further research.

中文翻译：

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生态系统工程师在塑造干旱土壤细菌群落的多样性和功能方面的作用

生态系统工程师 (EE) 存在于每个环境中，众所周知，它们会强烈影响生态过程，从而影响物种和资源的分布。在这项研究中，我们评估了两种 EE（多年生灌木和蚁巢）单独和组合对干旱土壤细菌群落的组成和功能的直接和间接影响。为此，在旱季期间在内盖夫沙漠高地从四种斑块类型收集表土样品：（1）贫瘠土壤；(2) 灌木下；(3)靠近蚁巢；或 (4) 靠近位于灌木下的蚂蚁巢穴。使用 16S rRNA 基因扩增子测序以及土壤的物理化学测量，在土壤样品中评估细菌群落组成和潜在功能（每个斑块类型 14 个重复）。我们发现 EE 对社区组成的影响不同。贫瘠的斑块支持土壤微生物组，主要由Rubrobacter和 Proteobacteria，而在 EE 补丁中，Deinococcus-Thermus 占主导地位。EEs 的存在同样增强了光养、氮循环和胁迫相关基因的丰度。此外，只有当两种 EE 结合时，土壤特性才会改变。我们的结果表明，干旱景观培养了由每个 EE（s）单独或组合创建的补丁选择的独特社区。尽管社区的组成不同，但它们支持相似的潜在功能，可能在恶劣的干旱条件下生存。EEs 对土壤微生物群落的综合影响是干旱生态系统难以预测的非加性特征的一个很好的例子，值得进一步研究。