DataSheet_2_Bacterial Diversity and Interaction Networks of Agave lechuguilla Rhizosphere Differ Significantly From Bulk Soil in the Oligotrophic Basin of Cuatro Cienegas.xlsx

Due to the environmental conditions presented in arid zones, it is expected to have a high influence of deterministic processes over the community assemblages. Symbiotic interactions with microorganisms could increase colonization and survival of plants in difficult conditions, independent of the plants physiological and morphological characteristics. In this context, the microbial communities associated to plants that inhabit these types of areas can be a good model to understand the community assembly processes. We investigated the influence of stochastic and deterministic processes in the assemblage of rhizosphere microbial communities of Agave lechuguilla and bulk soil on the Cuatro Cienegas Basin, a site known for its oligotrophic conditions. We hypothesize that rhizospheric microbial communities of A. lechuguilla differ from those of bulk soil as they differ in physicochemical properties of soil and biotic interactions, including not only the plant, but also their microbial co-occurrence networks, it is expected that microbial species usually critical for plant growth and health are more common in the rhizosphere, whereas in the bulk soil microbial species related to the resistance to abiotic stress are more abundant. In order to confirm this hypothesis, 16S rRNA gene was sequenced by Illumina from rhizospheric and bulk soil samples in two seasons, also the physicochemical properties of the soil were determined. Our results showed differences in bacterial diversity, community composition, potential functions, and interaction networks between the rhizosphere samples and the ones from bulk soil. Although community structure arises from a complex interplay between deterministic and stochastic forces, our results suggest that A. lechuguilla recruits specific rhizospheric microbes with functional traits that benefits the plant through growth promotion and nutrition. This selection follows principally a deterministic process that shapes the rhizospheric microbial communities, directed by the plant modifications around the roots but also subjected to the influence of other environmental variables, such as seasonality and soil properties. Interestingly, keystone taxa in the interactions networks, not necessarily belong to the most abundant taxonomic groups, but they have an important role by their functional traits and keeping the connections on the community network.

鉴于干旱地带的环境特征，确定性过程对群落组装的影响预计将占据主导地位。与微生物的共生互作可提升植物在恶劣环境中的定殖与存活能力，且该效应独立于植物自身的生理与形态学特性。在此背景下，栖息于此类区域的植物相关微生物群落，可作为解析群落组装过程的优质模型。本研究针对以寡营养环境特征闻名的锡沃斯盆地（Cuatro Cienegas Basin），探究了随机过程与确定性过程对莱丘盖拉龙舌兰（Agave lechuguilla）根际（rhizosphere）微生物群落与非根际土壤（bulk soil）组装过程的影响。我们提出如下假说：由于土壤理化性质与生物互作（不仅包括植物本身，还包括微生物的共现网络）存在差异，莱丘盖拉龙舌兰的根际微生物群落与非根际土壤微生物群落结构有所不同；预计根际中对植物生长与健康至关重要的微生物类群更为富集，而非根际土壤中与抗非生物胁迫相关的微生物类群占比更高。为验证该假说，本研究于两个季节采集根际与非根际土壤样本，通过Illumina测序平台对16S核糖体RNA（16S rRNA）基因进行测序，并测定了土壤的理化性质。研究结果显示，根际样本与非根际土壤样本在细菌多样性、群落组成、潜在功能以及互作网络方面均存在显著差异。尽管群落结构是确定性与随机过程共同复杂互作的结果，但本研究结果表明，莱丘盖拉龙舌兰会招募具有特定功能性状的根际微生物，通过促进植物生长与营养吸收为植株带来益处。这种微生物招募过程主要遵循由植物根系周围环境改造所驱动的确定性过程，同时也受季节变化、土壤性质等其他环境变量的影响。有趣的是，互作网络中的关键类群（keystone taxa）未必隶属于丰度最高的分类单元，但其凭借自身的功能性状以及对群落网络连接性的维系作用，发挥着重要的生态功能。