Abstract
Plant growth-promoting rhizobacteria (PGPR) are bacteria known to enhance plant growth via nitrogen fixation, nutrient solubilization, and phytohormone production. Within the rhizosphere, these bacteria engage in complex intra- and interspecies communication, often mediated by volatile organic compounds (VOCs). VOCs influence microbial behavior, metabolism, and stress responses, yet their specific metabolic impacts remain underexplored. This study applied untargeted metabolomics to investigate VOC-mediated interactions between PGPR strains Priestia megaterium and Bacillus licheniformis. Using a split petri dish co-cultivation system, we assessed time-dependent changes (days 3, 6, 9) in endo- and exo-metabolomes. Phenotypically, B. licheniformis displayed filamentous growth, emerging by day 6 in co-culture but only by day 9 in monoculture, suggesting accelerated morphological adaptation via VOC signaling. Metabolic profiling and multivariate analysis further revealed significant metabolic shifts under co-cultivation, highlighting the strong influence of VOCs on microbial metabolism. In co-culture, P. megaterium showed increased secretion of amino acids (e.g. proline, valine) nucleobases (e.g. thymine) and secondary metabolites (macrolactins, bacilliskamide A, oxydifficidin), suggesting VOC-driven activation. In contrast, B. licheniformis downregulated secondary metabolite secretion, indicating a trade-off favoring intracellular metabolite retention. Key adaptive response involved metabolic routes related to amino acid use and nitrogen recycling, including pathways for lysine and arginine breakdown, which support energy generation and cellular protection. These findings reveal that VOC-mediated interactions trigger species-specific metabolic reprogramming, influencing microbial dynamics and potentially enhancing plant-microbe associations, with implications for sustainable agriculture.