The prevalence and distribution of Acidobacteriota in the Nama Karoo of South Africa

The phylum <i>Acidobacteriota</i> is ubiquitous and a dominant bacterial group in arid lands, playing a crucial role in nutrient cycling and ecosystem functioning. This study explores <i>Acidobacteriota</i> 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). <i>Acidobacteriota</i> 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 <i>Planctomycetota</i> and <i>Armatimonadota</i> suggest potential biofilm formation and shared ecological niches. This study provides the first comprehensive assessment of <i>Acidobacteriota</i> 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.