Microbioma associado à Mimosa tenuiflora (Willd.) Poir. em área suscetível à desertificação da caatinga e o potencial funcional de bactérias endofíticas para a recuperação de áreas degradadas

Abstract

Desertification in the Brazilian semiarid region poses a growing threat to Caatinga biodiversity and ecosystem services. Mimosa tenuiflora (Willd.) Poir. (jurema-preta) stands out as a dominant pioneer species in degraded areas and for its contribution to natural regeneration; however, the microbiological mechanisms underlying its resilience remain poorly understood. This study aimed to characterize the bacterial microbiome associated with the rhizosphere and root endosphere of M. tenuiflora in an area susceptible to desertification and evaluate the effect of endophytic bacterial inoculation on seedling early development. To this end, the root bacterial microbiome of M. tenuiflora was characterized for the first time in the municipality of Irauçuba, Ceará state, through amplicon sequencing of the 16S rRNA gene V4 region. Libraries were normalized by rarefaction (60,000 reads/sample) and analyzed for alpha diversity, beta diversity, and taxonomic composition. The rhizosphere exhibited significantly higher alpha diversity than the endosphere, a pattern consistent with progressive host-mediated filtering. Beta diversity analysis revealed significant compositional differentiation between compartments (PERMANOVA: R² = 0.536, p = 0.009), with greater rhizospheric homogeneity and endospheric heterogeneity. At the phylum level, Pseudomonadota dominated the endosphere, while Actinomycetota was more abundant in the rhizosphere. Differential abundance analysis identified 11 significantly enriched genera (p-adj < 0.05, |log2FC| ≥ 2): 10 in the rhizosphere (Conexibacter, Neobacillus, Crossiella, among others) and one in the endosphere (Rhizobium). The endosphere was dominated by the Burkholderia-Caballeronia-Paraburkholderia complex, known for symbiotic nitrogen fixation and multiple plant growth-promoting capabilities, followed by Klebsiella and Mycobacterium. The results reveal functional partitioning between compartments, with endospheric specialization in nutrient provisioning and stress mitigation versus maintenance of rhizospheric diversity related to decomposition and nutrient cycling. In vitro inoculation experiments with M. tenuiflora seedlings demonstrated that the Serratia rubidaea + Citricoccus sp. endophytic consortium promoted increased root growth compared to the control (p.adj < 0.05), confirming the potential of native strains to promote plant growth. This structuring constitutes an adaptive strategy to desertification conditions, explaining the resilience of M. tenuiflora in degraded soils and providing the basis for bioinoculant development and Caatinga ecological restoration strategies.