New discovery links microbes, plants in the face of sulphur shortage
Scientists from the Singapore Centre for Environmental Life Sciences Engineering (SCELSE) and the National University of Singapore (NUS) have uncovered a surprising strategy by which plants can thrive when sulphur, an essential nutrient, is in short supply. In a study published in Cell Host & Microbe on 26 September 2025, the researchers describe a trans-kingdom interaction in the rhizosphere—the soil zone around plant roots—where microbial competition triggers a protective boost for plants.
The core finding: when soil bacteria compete for nutrients, they release glutathione, a well-known molecule that among other roles helps cells cope with stress. In the context of sulphur deficiency, this glutathione enhances plant growth and resilience. However, the price of this boost is paid by the microbes themselves, which experience reduced growth. The team refers to this as a “trans-kingdom fitness trade-off,” highlighting a balance where one kingdom (plants) gains fitness at the expense of another (microbes).
Why sulphur matters and what’s happening in the soil
Sulphur plays a central role in protein synthesis, vitamin formation, and stress responses in plants. Historically, atmospheric sulphur pollution replenished soils and helped maintain crop nutrition. With cleaner energy systems and stricter air-quality rules, atmospheric sulphur levels have fallen, leading to lower natural sulphur deposition in agricultural soils. As crops deplete the remaining sulphur over time, farmers have increasingly relied on synthetic sulphur fertilisers. While efficient in the short term, these measures can contribute to nutrient runoff, waterway pollution, and broader ecological degradation.
The mechanism: glutathione as a bridge between kingdoms
The SCELSE-NUS team investigated the rhizosphere where microbes and plant roots interact closely. Their findings show that microbial competition prompts the release of glutathione. This molecule, in the right context, acts to boost plant growth when sulphur is scarce. From an evolutionary perspective, the result is a trans-kingdom cooperative effect: plants receive a performance edge under nutrient stress, while the microbial community pays a cost in its own growth.
As first author Arijit Mukherjee explains, plant fitness is not determined by the plant alone but by the broader microbial consortium around it. Understanding these trade-offs provides a framework for designing microbial solutions that support crops under challenging soil conditions.
Implications for agriculture: from insight to application
The discovery shifts how researchers think about sustainable farming. Rather than relying solely on chemical inputs, scientists can design microbial consortia—carefully engineered “cocktails” of beneficial microbes—that naturally bolster crop health under sulphur limitation. This approach promises to improve soil health, reduce fertiliser use, and contribute to global food security in the face of environmental change.
Associate Professor Sanjay Swarup, a principal investigator at SCELSE and a key author, emphasizes the broader potential: “This study provides a blueprint for sustainable agriculture. By tapping into natural plant–microbe partnerships, we can reduce fertiliser use, protect ecosystems, and still secure global food supplies.” Swarup also notes that the work informs practical routes toward climate-ready farming through more resilient holobionts—the combined unit of host plants and their microbial partners.
From discovery to the clinic of fields: patent and next steps
To translate the mechanism into real-world products, the team has filed a patent covering applications of the plant–microbe interaction for agriculture. The goal is to develop bio-based products that support crops in sulphur-deficient soils, reducing the need for chemical inputs and lessening environmental impact. This forward path combines microbiology, soil science, and agronomy to create tangible tools for farmers.
Assosiate Professor Swarup underscores the broader scientific message: beyond plants and microbes, similar trans-kingdom trade-offs may be widespread across host–microbe systems. Recognising these hidden strategies could unlock new approaches to resilience in agriculture and beyond.
Conclusion
The discovery of the trans-kingdom fitness trade-off offers a powerful lens on how nature quietly balances life in the rhizosphere. By harnessing microbial glutathione signaling, we can craft sustainable, soil-friendly strategies to keep crops thriving under nutrient stress, contributing to resilient food systems in a changing world.
