28-07-2025
Methane-eating bacteria isolated from tropical wetlands in western Maharashtra by scientists
PUNE: In what marks the first time such extensive cultivation of Methanotrophs has been achieved in India's tropical ecosystem, a team of scientists from the Agharkar Research Institute comprising Kajal Pardhi, Rahul Bahulikar, and Monali Rahalkar has successfully isolated and characterised a wide variety of methane-eating bacteria also known as Methanotrophs from the tropical wetlands across western Maharashtra. These microorganisms serve as Nature's methane scrubbers, consuming the potent greenhouse gas before it escapes into the atmosphere. Methane-eating bacteria isolated from tropical wetlands in western Maharashtra by scientists
Samples were collected from various wetlands including freshwater ponds, lake sediments, stone quarries, and mangroves. Through an advanced serial dilution and long-term incubation technique, researchers managed to isolate 20 Methanotroph monocultures (90% purity), eight of which were fully purified to 100%. Using gene markers such as pmoA, a gene directly involved in methane oxidation, and 16S rRNA for further confirmation, the researchers identified seven different methanotroph genera: Methylomonas, Methylocystis, Methylosinus, Methylocaldum, Methylocucumis, Methylomagnum and Methylolobus.
Pardhi, lead scientist of the study, said, 'It is very difficult to isolate and cultivate Methanotrophs because they usually come along with many other bacteria, and pure cultivation takes years. In our research, which took nearly two to three years, we successfully isolated and cultivated around 28 Methanotrophs, including two newly-discovered genera Methylocucumis and Methylolobus. These have not been reported anywhere in the world yet. The important thing is that these are cultivable strains, which means we can now grow them in the lab with minimal contamination and apply them to real-world scenarios like methane mitigation in rice fields and wetlands. Methanotrophs not only help reduce methane, a major greenhouse gas, but also promote plant growth. Our approach makes it possible to use these native strains in agriculture and environmental management to address climate change from the ground up.'
Two genera stood out in prevalence namely type I Methylomonas and type II Methylocystis, underscoring their key role in methane cycling in tropical wetlands. Interestingly, habitat-specific patterns emerged from the study. Freshwater ponds showed the highest Methanotroph densities up to 10¹² cells per gram of soil while mangrove samples had significantly lower concentrations. Additionally, heat-tolerant strains like Methylocaldum were found mainly in mangrove ecosystems, whereas freshwater zones hosted only mesophilic strains.
A particularly striking achievement was the successful isolation of rare and understudied Methanotroph genera. Strains of Methylocucumis, a genus previously uncultured anywhere else in the world, and Methylolobus were cultivated for the first time. One standout strain, Methylolobus aquaticus PLW4, is only the second known isolate of its kind globally. The team also identified Methylomagnum, previously associated only with rice paddies, in a wetland sample widening the known ecological range of the genus.
Pardhi said, 'Methanotrophs act as Nature's methane filters. In our latest research, we have cultivated seven different genera of Methanotrophs from the Pune wetlands, making this the first report of its kind from Indian wetlands. Until now, no biodiversity studies or cultivation work had been carried out on Methanotrophs. These organisms play a critical role in mitigating methane, a potent greenhouse gas, by oxidising it naturally in wetland sediments. Our lab is the first in India to successfully culture these bacteria using advanced techniques developed over the last decade. Our focus was on reporting their biodiversity, especially in regions like the western Ghats, a global biodiversity hotspot.'
Rahalkar said, 'If Methanotrophs did not exist, atmospheric methane levels would have been far higher, possibly making the planet uninhabitable. These microbes are Nature's unseen warriors against climate change.'
Beyond their role in mitigating methane emissions, these cultivated Methanotrophs open new avenues for biotechnology. Scientists see potential in transforming methane into valuable products like carotenoids (used in food and pharma), biodegradable plastics like polyhydroxyalkanoates (PHAs), and high-protein single-cell biomass for animal feed. This landmark research places India on the global map for methane bioremediation innovation and could serve as a foundation for sustainable climate solutions rooted in microbial ecology.
