Bacillus altitudinis GG-22: A novel plant growth-promoting bacterium with beneficial agronomic properties

Abstract

Bacillus altitudinis GG-22, isolated from the phyllosphere of agricultural crops, has been identified as a promising biocontrol agent and plant growth-promoting bacterium with substantial potential in sustainable agriculture. In this study, whole-genome sequencing using Illumina technology, combined with ANI analysis, confirmed the strain's classification as B. altitudinis. The genome revealed a rich set of genes involved in biocontrol mechanisms, including the capacity of synthesis of siderophores (schizokinen and bacillibactin-like compounds), the lipopeptide pumilacidin, the bacteriocin pumilarin, alkylpyrones and Bacillus volatiles. In vitro antagonism assays demonstrated significant inhibitory effects against phytopathogenic fungi and oomycetes, such as Verticillium dahliae and Pythium sp., and B. altitudinis GG-22 also showed limited efficacy against bacterial phytopathogens, including Xylella fastidiosa. Transcriptomic profiling of olive trees treated with GG-22 indicated early activation of auxin transport and systemic acquired resistance (SAR) pathways, alongside substantial downregulation of cell wall remodelling genes. These findings suggest that B. altitudinis GG-22 primes plant defence responses and modulates hormonal pathways critical for growth and stress resilience. Future research should prioritize optimizing application strategies and exploring synergies with other microbial agents to fully harness the biocontrol and growth-promoting potential of B. altitudinis GG-22. This strain holds promise for sustainable agricultural practices, particularly in controlling fungal diseases and improving plant performance under stress conditions.