- A new study suggests that cold-adapted microbes may act as a natural climate regulator, limiting greenhouse gas emissions as temperatures rise.
- Microbial cooperation helps stabilise fragile high-altitude ecosystems under changing climatic conditions.
- Tracking microbial communities could improve climate monitoring and reveal how warming reshapes Himalayan ecosystems.
Amid the mountain folds of eastern Ladakh’s Changthang plateau lies Tso Moriri, the highest Ramsar-listed wetland of international importance. Part of a Trans-Himalayan lake-desert ecosystem, the lake remains frozen for nearly one-third of the year and is surrounded by barren hills, broken only by small patches of green meadows and marshes along its northern and south-western shores.
These high-altitude ecosystems are increasingly vulnerable to climate warming. As summer arrives, Tso Moriri and the surrounding landscape begin to thaw, activating native microbes that can accelerate warming by releasing greenhouse gases.
A recent study led by Wriddhiman Ghosh, Professor, Department of Biological Sciences, Bose Institute, Kolkata, explored this process, hypothesising that as cold-adapted microbes become more active, they supply native methanogens — the methane-producing microbes — with compounds such as carbon dioxide and acetate. These compounds fuel methanogenesis, the final stage in the breakdown of organic matter, during which methanogens produce methane and carbon dioxide.
This creates a microbe-driven positive feedback loop: warming stimulates microbial activity, which releases more greenhouse gases, leading to further warming. The study set out to determine how strong this feedback could become.
Cold-adapted microbes
While deserts are ideal habitats for oligotrophic microbes that survive in nutrient-poor soil, the study focused on high-throughput copiotrophic microbes that thrive in nutrient-rich habitats. Copiotrophic microbes consume significantly larger amounts of complex organic matter and release plenty of simple organic matter into the environment.
Commenting on the choice of microbes for the study, Raju Biswas, a microbial ecologist and postdoctoral research associate at the Centre for Ecological Sciences, Indian Institute of Science, Bengaluru says, “Soils in high-altitude deserts are indeed nutrient-poor and therefore have more oligotrophs. But they are intrinsically slow, and the carbon they turn over and the greenhouse gases they emit may be too small to produce a detectable ecosystem signal.” Biswas was not involved in the study.
The researchers collected microbial samples from the lake’s brackish water and sediment surface just before the lake freezes in November, and also from the weathered rock dust on the slope of a lakeside hill.
Back in the laboratory, they retrieved the cold-adapted microbes through repeated freeze-thaw cycles and isolated 27 bacterial species. Genomic analysis of 15 selected isolates individually and as part of the microbial community from the three sampling sites were also carried out to understand the limits of microbe-mediated warming.
A microbe-mediated thermostat
As the researchers investigated the microbes’ performance at extreme temperatures, all the isolates showed optimal growth at 4°C and 15°C, and all remained at least metabolically active at -10°C, with some even exhibiting growth. However, they displayed progressive susceptibility to heat at higher temperatures: four isolates stopped growing at 28°C, while 16 isolates stopped at 37°C. The rest ceased to grow between 37°C and 42°C.
Based on these findings, the researchers suggest that the positive feedback loop can operate only within and around the 4-28°C temperature range. Above 28°C, as the copiotrophic microbes slow down, carbon dioxide and nitrous oxide outputs are curtailed and the supply of raw materials for methanogenesis dwindles, triggering a negative feedback loop that prevents further warming.
“This study’s main hypothesis that indigenous cold-adapted microbial communities could function like a biological thermostat, suppressing positive feedbacks of greenhouse gas warming, is both intellectually and ecologically sound,” comments Biswas. He also mentions that the presence of trace amounts of methanogens in the lake’s microbial community indicates the presence of this pathway on site and therefore justifies its modelling.
As populations of native microbes succumb to increasing heat in a progressive manner, the researchers also suggest that they could act as biogeothermometers or natural record-keepers of rising temperatures over time and space. “Monitoring how these microbial communities change over time along natural temperature gradients could offer a sensitive way to track the impacts of climate change in these high-altitude ecosystems. This approach could be valuable for long-term ecological monitoring programmes,” says Biswas.
An interactive microbial community
Individual and habitat-level genomic analyses of Tso Moriri isolates revealed the presence of copiotrophic microbes possessing several genes necessary for thermal adaptation and breaking down various carbohydrate compounds.
Rakshak Kumar, Associate Professor in the Department of Molecular Biology and Bioinformatics at Tripura University, Agartala, studies how microbes in extreme high-altitude environments respond to environmental change.
Kumar says that the study is significant as it extends physiological exploration beyond the commonly investigated thermal range of 4°C to 28°C and that the observations could improve our understanding of the lower thermal limits of indigenous microbial populations inhabiting extreme-cold ecosystems.
“The detection of diverse temperature-adaptation genes, carbohydrate-active enzymes, and metabolically relevant microbial groups suggests that ecosystem resilience could emerge from collective community interactions rather than from isolated taxa alone,” says Kumar.
Drawing on his research on Himalayan and glacier-associated bacterial communities in the Sikkim Himalaya, Kumar says that high-altitude habitats are protected not only by limiting the growth of microbes alone, but also by the way the entire microbial communities work together. Their ability to withstand harsh conditions, share resources, replace one another over time, and help stabilise the ecosystem, all contribute to keeping these fragile environments resilient.
Tightening the border control
As the term indicates, cold-adapted microbes are poor at adapting to increasing temperature. This constraint leaves them vulnerable to invasion by foreign heat-adapted microbes in a warming world.
Among the 27 isolated species in the study, 15 were Actinobacteria, microbes known for producing most naturally occurring antibiotic compounds and a majority of them were found to be thermotolerant and were able to inhibit the foreign microbes at 28°C.
Biswas notes that Actinobacteria are commonly the dominant microbes in the soils of cold environments. In this study, they made up 54% of the rock-dust microbial community, suggesting that the native microbial community is active rather than passive when faced with invading microbes.
As climate change increases the likelihood of foreign microorganisms reaching previously isolated cold habitats, Kumar emphasises that future research should examine how native microbes protect themselves. This includes understanding the role of antibiotic compounds they produce, the way different microbes occupy separate ecological niches, and how they cooperate to maintain the stability of these fragile ecosystems.
“The transition from laboratory experiments to a living ecosystem is very complicated. In the real world, these mechanisms are also influenced by factors such as local temperature variations, water availability, interactions among microbes, and repeated freeze-thaw cycles within microhabitats,” notes Biswas.
He points out the need for further field-based experiments in the natural temperature gradients in Ladakh.
“Such investigations help clarify that indigenous microbial communities respond to climate change not by ensuring their own survival, but by working together to protect their niche, maintain habitat stability, and strengthen environmental resilience,” Kumar points out.
Banner image: Tso Moriri lake during the summer, when the lake thaws and vegetation grows. Image by Raghavan37 via Wikimedia Commons (CC BY-SA 3.0).
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