Overview: A surprising alliance in the rhizosphere
Researchers from the Singapore Centre for Environmental Life Sciences Engineering (SCELSE) and the National University of Singapore (NUS) have uncovered a remarkable plant-microbe strategy that helps crops thrive when the essential nutrient sulphur is scarce. Published in Cell Host & Microbe on 26 September 2025, the study reveals how competing soil microbes release glutathione in the rhizosphere — the soil zone surrounding plant roots — to bolster plant growth under sulphur-deficient conditions. In a twist, this microbial generosity comes at a cost to their own growth, illustrating a trans-kingdom fitness trade-off.
The science behind the trade-off
Sulphur plays a critical role in protein synthesis, vitamin production, and stress resistance in plants. Historically, atmospheric deposition of sulphur from industrial pollution replenished soils. As cleaner energy and tighter air-quality rules reduced these inputs, soils gradually became sulphur-limited. Plants then rely more on microbial allies to access or liberate sulphur. The SCELSE-NUS team found that when soil bacteria compete for nutrients in the rhizosphere, they release glutathione — a powerful antioxidant and metabolite. This compound improves plant growth under sulphur stress, enabling greater shoot and root development, enzyme activity, and nutrient use efficiency.
However, the benefit to the plant comes with a drawback for the microbes: the release of glutathione correlates with reduced microbial growth. In essence, the plant gains resilience while some microbial players incur a growth penalty. The researchers describe this as a trans-kingdom fitness trade-off, a term that captures the balance of competing interests across different kingdoms of life in a shared environment.
Why this matters for agriculture
The discovery highlights that host-microbe systems may rely on hidden, community-level strategies to cope with nutrient stress. It suggests a broader principle: holobionts — the host plus its associated microbial community — can adapt collectively through shifts in microbial signaling and metabolism. For farmers and agronomists, the implication is profound: instead of solely relying on chemical fertilisers, scientists could design microbial consortia or “bio-enhancement cocktails” that naturally support crop health under nutrient deficits. Such bio-based solutions could reduce fertiliser runoff, improve soil structure, and enhance sustainability while helping secure global food production in the face of climate variability.
From discovery to practical applications
Assc Prof Sanjay Swarup, a senior researcher at SCELSE and Deputy Director for the NUS Environmental Research Institute, emphasizes the translational 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.” The team has already pursued practical steps, filing a patent covering applications of this plant-microbe mechanism in agriculture. The aim is to develop bio-based products that boost crops in sulphur-deficient soils and reduce reliance on chemical inputs.
Expert commentary: A broader horizon
The researchers note that trans-kingdom fitness trade-offs may be widespread across host-microbe systems, not limited to plants. Recognizing and leveraging these trade-offs could unlock new strategies for resilient crops and climate-ready farming. “Plant fitness isn’t just about the plant itself—it’s about the whole community of microbes around it,” said first author Arijit Mukherjee, highlighting the importance of considering microbial interactions in crop improvement programs.
Conclusion
As soils worldwide experience sulphur limitations, this study opens the door to nature-based approaches for sustaining yields. By engineering and deploying microbial consortia that support plant growth under nutrient stress, agriculture can move toward more resilient, environmentally friendly practices. The notion of a trans-kingdom fitness trade-off not only deepens our understanding of plant-microbe ecology but also charts a practical path toward sustainable food security.
