Scientists from the Singapore Centre for Environmental Life Sciences Engineering (SCELSE) - a biofilm & microbiome research centre - and the National University of Singapore (NUS), have uncovered a surprising strategy plants use to thrive when an essential nutrient - sulphur - is in short supply.
The team discovered that when soil microbes compete with each other in the rhizosphere (the soil surrounding plant roots), they release a well-known compound called glutathione. This compound enhances plant growth under sulphur-deficient conditions. The catch: while plants benefit, some microbes lose out in their own growth.
The researchers call this balancing act a "trans-kingdom fitness trade-off" - where one kingdom of life (microbes) sacrifices part of its growth, while another (plants) gains resilience.
The global problem: declining sulphur in soils
Sulphur is essential for plant growth, just like nitrogen and phosphorus. It supports protein synthesis, vitamin production, and stress resistance.
Historically, sulphur pollution from industrial emissions replenished soils worldwide. But with cleaner energy and stricter air-quality regulations, atmospheric sulphur levels have dropped. While good for air quality and human health, this has unintentionally reduced natural sulphur deposits in agricultural soils.
Over time, crops have drawn down existing soil sulphur, leaving soils deficient. To compensate, farmers increasingly apply synthetic sulphur-based fertilisers. These short-term fixes come with costs: runoff from farmlands contaminates rivers, lakes, and ecosystems, exacerbating environmental degradation.
The new discovery: a microbial boost
The SCELSE-led study, published in Cell Host & Microbe on 26 September 2025, provides a novel mechanistic explanation of how plants and microbes jointly navigate nutrient stress. The researchers found that when soil bacteria compete for nutrients, they release glutathione - a compound that boosts plant growth under sulphur-deficient conditions, even though it reduces bacterial growth.
This improvement in plant fitness came at the cost of bacterial fitness - a biological trade-off across kingdoms of life.
"This work introduces the concept of a trans-kingdom fitness trade-off and provides a mechanistic explanation for it," said first author Arijit Mukherjee, who was a PhD student at SCELSE and the NUS Department of Biological Sciences when the study was conducted. "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."
Why it matters
Such trade-offs are likely widespread across host-microbe systems, not just in plants, and may represent hidden strategies by which holobionts (hosts and their associated microbes) adapt collectively to environmental cues.
For agriculture, this insight is powerful: instead of relying on chemical fertilisers, researchers can design microbial consortia (or "cocktails") that naturally boost crop health under nutrient stress. This nature-based solution can reduce fertiliser use, improve soil health, and contribute to global food security.
Assoc Prof Sanjay Swarup, Principal Investigator at SCELSE, explained, "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."
From discovery to application: patent filed
To translate this breakthrough into practice, the team has filed a patent covering applications of this plant-microbe mechanism in agriculture. This will enable the development of bio-based products that support crops in sulphur-deficient soils, reducing reliance on chemical inputs.
"By considering not only microbial functions but also their interactions, we can design more effective microbial consortia for agriculture," added Assoc Prof Swarup, who is also the Deputy Director for NUS Environmental Research Institute (NERI) and a faculty member of the NUS Department of Biological Sciences. "This is the path toward resilient, climate-ready farming."
