Endophytic Bacteria from the Desiccation-Tolerant Plant Selaginella lepidophylla and Their Potential as Plant Growth-Promoting Microorganisms

Bacteria associated with plants, whether rhizospheric, epiphytic, or endophytic, play a crucial role in plant productivity and health by promoting growth through complex mechanisms known as plant growth promoters. This study aimed to isolate, characterize, identify, and evaluate the potential of endophytic bacteria from the resurrection plant <i>Selaginella lepidophylla</i> in enhancing plant growth, using <i>Arabidopsis thaliana</i> ecotype Col. 0 as a model system. Plant growth-promotion parameters were assessed on the bacterial isolates; this assessment included the quantification of indole-3-acetic acid, phosphate solubilization, and biological nitrogen fixation, a trehalose quantification, and the siderophore production from 163 endophytic bacteria isolated from <i>S. lepidophylla</i>. The bacterial genera identified included <i>Agrobacterium</i>, <i>Burkholderia</i>, <i>Curtobacterium</i>, <i>Enterobacter</i>, <i>Erwinia</i>, <i>Pantoea</i>, <i>Pseudomonas</i>, and <i>Rhizobium</i>. The plant growth promotion in <i>A. thaliana</i> was evaluated both in Murashige Skoog medium, agar-water, and direct seed inoculation. The results showed that the bacterial isolates enhanced primary root elongation and lateral root and root hair development, and increased the fresh and dry biomass. Notably, three isolates promoted early flowering in <i>A. thaliana</i>. Based on these findings, we propose the <i>S. lepidophylla</i> bacterial isolates as ideal candidates for promoting growth in other agriculturally important plants.