Isolation and functional characterization of culturable endophytic bacteria from Alhagi sparsifolia Shap.

Abstract:

[Background] Endophytes represent valuable resources for investigating microbial diversity and adaptive evolution, owing to their long-term co-evolutionary relationship with their hosts. Alhagi sparsifolia Shap. exhibits robust tolerance to stress conditions including drought and saline-alkali. However, the studies about the endophytes of A.sparsifolia remain limited. [Objective] To analyze the diversity of culturable endophytic bacteria and evaluate the stress tolerance and plant growth-promoting effects of the strains. [Methods] Endophytic bacteria were isolated from A.sparsifolia by the tissue homogenization and gradient dilution methods. The strains were identified by comparison of 16S rRNA gene sequences. Subsequently, we determined the stress tolerance, plant growth-promoting effects, and antimicrobial activities of the strains. [Results] A total of 14 culturable endophytic bacterial strains were isolated from A.sparsifolia, belonging to 9 genera (Bacillus, Brachybacterium, Microbacterium, Corynebacterium, Solibacillus, Glutamicibacter, Leucobacter, Brevibacterium, and Acinetobacter), among which Bacillus was dominant (33.33%). These strains exhibited varying levels of stress tolerance, plant growth-promoting effects, and antimicrobial activities. Notably, Bacillus subtilis L-1 demonstrated strong tolerance to 20% NaCl solution and 20% PEG6000 and inhibitory effects on four pathogenic bacterial species and three pathogenic fungal species. [Conclusion] Our study revealed the stress tolerance, plant growth-promoting effects, and antimicrobial activities of culturable endophytic bacterial resources in A.sparsifolia. The findings provide a scientific basis for further exploration and utilization of these valuable resources.