Supplementary file 1_The prevalence and distribution of Acidobacteriota in the Nama Karoo of South Africa.docx

The phylum Acidobacteriota is ubiquitous and a dominant bacterial group in arid lands, playing a crucial role in nutrient cycling and ecosystem functioning. This study explores Acidobacteriota in Southern African arid lands through two complementary approaches. A meta-analysis of 240 soil samples revealed relative abundances ranging from 0.008% to 39.1%, with pH identified as the primary driver of community variance. In addition, 96 bulk soil samples from the Nama Karoo were analyzed using full-length 16S rRNA gene sequencing (V1–V9). Acidobacteriota abundance ranged from 2.3% to 12.2%, with Subdivisions 3, 4, and 6 being the most dominant, while rare subdivisions, such as 2 and 9, showed location-specific distributions. Significant beta-diversity differences (p = 0.002) were linked to soil moisture, electrical conductivity, and nitrate availability, and some subdivisions exhibited correlations with organic carbon and nitrate. Co-occurrence patterns with Planctomycetota and Armatimonadota suggest potential biofilm formation and shared ecological niches. This study provides the first comprehensive assessment of Acidobacteriota in Southern African arid lands, highlighting dominant and rare subdivisions, localized ecological associations, and the need for future work on their metabolic functions and adaptive strategies in arid ecosystems.

酸杆菌门（Acidobacteriota）是一类广布的细菌类群，在干旱陆地生态系统中占据优势地位，在养分循环与生态系统功能维持中发挥关键作用。本研究采用两种互补的研究方法，对南非干旱陆地生境中的酸杆菌门类群展开探究。对240份土壤样本开展的荟萃分析（meta-analysis）显示，其相对丰度区间为0.008%至39.1%，其中pH值被确定为驱动群落组成差异的首要因子。此外，研究团队针对纳马卡鲁（Nama Karoo）地区的96份原状土壤（bulk soil）样本，采用全长度16S rRNA基因测序（V1–V9区）技术进行分析。结果表明，酸杆菌门的丰度区间为2.3%至12.2%，其中亚类3、4和6为优势类群；而稀有亚类（如亚类2和9）则呈现出地点特异性的分布模式。显著的β多样性差异（p = 0.002）与土壤含水量、电导率及硝酸盐有效性密切相关，部分亚类与有机碳和硝酸盐含量存在显著相关性。酸杆菌门与浮霉菌门（Planctomycetota）、铠甲菌门（Armatimonadota）的共现模式提示，二者可能具备潜在的生物膜形成能力并共享生态位。本研究首次对南非干旱陆地生境中的酸杆菌门类群进行了全面评估，明确了优势与稀有亚类的分布特征、局域生态关联，并指出未来需进一步探究其在干旱生态系统中的代谢功能与适应策略。