Groundbreaking discovery reveals how microbes aid plants under sulfur stress
Scientists from the Singapore Centre for Environmental Life Sciences Engineering (SCELSE) and the National University of Singapore (NUS) have uncovered a surprising plant-microbe strategy that helps crops grow when the essential nutrient sulfur is scarce. In a study published in Cell Host & Microbe on 26 September 2025, the researchers show that soil bacteria competing in the rhizosphere — the zone of soil surrounding plant roots — release glutathione, a well-known antioxidant and facilitator of nutrient use. This compound boosts plant growth under sulfur-deficient conditions, even as it reduces the growth of the very microbes that produce it. The team calls this a “trans-kingdom fitness trade-off,” a balancing act across the lines of life between microbes and plants.
What the study found
Sulfur is vital for protein synthesis, vitamin production, and stress resilience in plants. Historically, atmospheric sulfur pollution replenished soils, but stricter air-quality controls have reduced this natural input. As soil sulfur declines, crops increasingly rely on synthetic sulfur fertilisers, which pose environmental challenges such as nutrient runoff. Against this backdrop, the SCELSE–NUS team explored how microbial communities respond to nutrient limitation and how their interactions influence plant performance.
The key result: when microbes compete for limited nutrients, they release glutathione into the rhizosphere. Plants living in this microbially active environment show improved growth despite low sulfur availability, while the producing microbes incur a cost to their own growth. In short, the plant benefits from a microbial exchange that comes at the microbes’ expense — a clear case of trans-kingdom fitness trade-off.
Insights from the researchers
First author Arijit Mukherjee, then a PhD student at SCELSE and the NUS Department of Biological Sciences, notes that plant fitness depends on the broader microbial community. “Plant fitness isn’t just about the plant itself — it’s about the whole community of microbes around it. Understanding these trade-offs helps us design better microbial solutions for resilient crops,” he said. Associate Professor Sanjay Swarup of SCELSE emphasizes the broader significance: this trade-off likely exists in other host–microbe systems and offers a blueprint for sustainable agriculture that leverages natural partnerships rather than chemical inputs.
Why this matters for agriculture and sustainability
The discovery points toward new, nature-based strategies to bolster crop performance under nutrient stress. By engineering or selecting microbial consortia — effectively “bio-based cocktails” — farmers could reduce dependence on chemical fertilisers, improve soil health, and contribute to food security in a climate- and resource-constrained world. Swarup, who leads SCELSE’s research program and serves as Deputy Director for NUS Environmental Research Institute, frames the work as a practical path to resilient, climate-ready farming: “By tapping into natural plant–microbe partnerships, we can reduce fertiliser use, protect ecosystems, and still secure global food supplies.”
From discovery to potential applications
The team has moved toward translation with a patent filing that covers the agricultural applications of this plant–microbe mechanism. The goal is to develop bio-based products capable of supporting crops in sulfur-deficient soils, reducing environmental impact while maintaining yields. The work highlights the importance of considering microbial interactions, not just individual microbial functions, in designing effective agricultural solutions.
Looking ahead
Beyond its immediate agricultural implications, the study suggests that trans-kingdom fitness trade-offs may be common across holobiont systems — hosts plus their associated microbes — and could represent a hidden mechanism by which ecosystems adapt to changing conditions. As researchers continue to decode these cross-kingdom relationships, farmers, biotechnologists, and policymakers may gain new tools for promoting sustainable agriculture in the face of nutrient limits and climate variability.
