Characterization of Soil Microbial Communities Associated with the Sustainability of Acacia Species in the Imam Turki Bin Abdullah Royal Reserve, Saudi Arabia
Abstract
The Imam Turki bin Abdullah Royal Reserve, one of Saudi Arabia’s largest protected areas, harbors extensive Acacia populations whose rhizosphere microbiota enhance nutrient availability and ecosystem sustainability. The present study aimed to characterize the soil and plant nutrient status alongside the composition of microbial communities of two Acacia species to support biodiversity conservation and desertification mitigation. Fifteen paired leaf and rhizosphere soil samples were collected from Acacia gerrardii Benth (n = 9) and Acacia raddiana Savi (n = 6). The two plant groups exhibited distinct macro- and micro-elemental profiles, indicating variations in nutrient availability across the sampled habitats. Amplicon-sequencing revealed diverse bacterial communities, with Actinobacteriota, Chloroflexi, and Proteobacteria representing the dominant bacterial phyla. The genus JG30-KF-CM45 (Chloroflexi) was particularly abundant in several soil samples. Likewise, fungal communities were overwhelmingly dominated by Ascomycota, whereas Basidiomycota occurred at lower abundance. Didymella, Pithoascus, and Fusarium were among the most prevalent fungal taxa. Functional predictions indicated significant variation in enzymes associated with nutrient transformation and microbial metabolism, involving Zinc D-Ala-D-Ala carboxypeptidase, serine-type D-Ala-D-Ala carboxypeptidase, amidase, UDP-N-acetylglucosamine 1-carboxyvinyltransferase, and α-amylase. In addition, the KEGG Orthologs (KOs), K08640 (zinc D-Ala-D-Ala carboxypeptidase), K00657 (diamine N-acetyltransferase) and K06147 (ATP-binding cassette, subfamily B), had the highest relative abundances in bacterial communities. These findings highlight distinct rhizosphere microbial assemblages associated with Acacia species, which may contribute to plant performance and ecosystem functioning in arid environments.