Ralstonia solanacearum is a soil-borne bacterial pathogen that threatens over 100 crop species, including tomatoes. Traditional disease management is limited in efficacy, leading researchers to explore microbiome-based solutions. Plant roots host diverse bacterial communities that can suppress pathogens by secreting antimicrobial compounds or outcompeting invaders for resources. Among these mechanisms, iron competition plays a pivotal role, as iron is scarce in the rhizosphere but essential for microbial metabolism. To cope, many microbes produce siderophores to scavenge iron. While their role in individual strain performance is well-documented, how siderophores mediate interspecies interactions in complex consortia remains poorly understood. Due to these challenges, deeper investigations into microbiome interactions are urgently needed.
Researchers from Nanjing Agricultural University, in collaboration with French and Chinese institutions, published (DOI: 10.1093/hr/uhae186) their findings in Horticulture Research on July 12, 2024. The study, titled “Siderophore interactions drive the ability of Pseudomonas spp. consortia to protect tomato against Ralstonia solanacearum,” reveals how microbial cooperation under iron-limited conditions can suppress bacterial wilt in tomato. By assembling consortia from seven Pseudomonas strains and testing them under varied iron conditions, the team identified siderophore-mediated interactions as the key to effective pathogen control.
The team constructed 49 Pseudomonas consortia and tested their ability to suppress R. solanacearum under iron-rich and iron-limited conditions. In co-culture and supernatant assays, they found that siderophore production was upregulated in low-iron environments, enhancing pathogen inhibition. Notably, siderophores outperformed other secondary metabolites—such as 2,4-diacetylphloroglucinol (DAPG)—under iron deficiency. However, the total amount of siderophores produced was not the best predictor of pathogen suppression. Instead, the strength of siderophore-mediated interactions within consortia—how bacterial strains affected one another’s growth via siderophores—correlated most strongly with disease resistance. One key finding was that some strains, such as F113, produced siderophores that paradoxically promoted pathogen growth, underscoring the complexity of interspecies interactions. Structural equation modeling and greenhouse experiments confirmed that consortia with stronger internal competition for iron exhibited better suppression of bacterial wilt. These results suggest that siderophores not only starve pathogens of iron but also shape the dynamics within beneficial communities, enhancing their stability and functionality. Importantly, interactions—not merely metabolite levels—are the decisive factor in biocontrol performance.
“Siderophores have long been recognized for their role in microbial iron acquisition, but this study demonstrates their deeper ecological significance,” said Dr. Tianjie Yang, corresponding author of the study. “What we found is that the way bacteria interact through siderophores within a consortium matters more than how much they produce. This opens new possibilities for engineering microbial communities that are robust, cooperative, and highly effective at suppressing plant diseases, especially under nutrient stress conditions.”
The findings offer valuable insights for designing next-generation biofertilizers and microbial consortia for sustainable agriculture. Instead of focusing solely on individual strains or metabolite output, agricultural microbiome engineering should consider interaction strength—especially siderophore-mediated competition—as a key design principle. In iron-limited soils, such as those common in tomato cultivation, promoting beneficial microbial iron competition could serve as a natural defense against bacterial wilt. This research advances the development of community-based biocontrol strategies that are both environmentally friendly and resilient to pathogen invasion, potentially reducing reliance on chemical pesticides and improving food security.
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References
DOI
10.1093/hr/uhae186
Original Source URL
https://doi.org/10.1093/hr/uhae186
Funding information
This research was funded by the National Natural Science Foundation of China (42090060, 42325704, 42277113, and 42107140), the Fundamental Research Funds for the Central Universities (KYT2024001), the Natural Science Foundation of Jiangsu Province (BK20230102), the Jiangsu Agricultural Science and Technology Innovation Fund (CX(22)1004, SCX(24)3511) and the Jiangsu Carbon Peak & Carbon Neutrality Science and Technology Innovation Special Fund (BE2022423).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.