Article ID: 25.0328a
Bacillus pumilus TUAT1, a gram-positive and spore-forming plant growth-promoting rhizobacterium, has been utilized as a biofertilizer due to its robust ability as spores to withstand environmental stresses and ensure long-term viability. This study investigated the mechanisms underlying the plant growth-promoting effects of spores and vegetative cells. Elemental analyses revealed that endospores are enriched in carbon, calcium, and manganese, which contribute to their protective properties, while vegetative cells are richer in nitrogen and phosphorus. Notably, both viable and dead spores and vegetative cells promoted the growth of Setaria viridis in natural soil. Microbial community analysis showed that bacterial alpha diversity was not changed across treatments, whereas beta diversity varied significantly, forming distinctly separated groups influenced by planting and inoculation. Fungal community analysis exhibited increased alpha diversity due to Setaria planting but no significant effects from bacterial treatments. Enrichment of Bdellovibrio spp., Bacteriovorax spp., and Pseudomonas spp. in soil inoculated with viable and dead vegetative cells and spores highlighted the capability of indirect mechanisms through microbial interactions rather than direct nutrient supply from bacterial residues. We believe that bacterial inoculants, including dead cells, modulate soil microbial communities to enhance plant growth, emphasizing their potential in sustainable agriculture.
