In a major scientific breakthrough from Northeast India, researchers from the Department of Environmental Science, Tezpur University, Assam, in collaboration with Visva-Bharati University, have discovered a bacterium inside an earthworm’s gut that can break down chrysene—a hazardous petroleum-based pollutant known for its cancer-causing properties.
The findings, published in the Journal of Hazardous Materials, could pave the way for sustainable and low-cost solutions to clean oil-contaminated soils in the region.
Why This Matters for the Northeast
Chrysene belongs to a group of toxic compounds called polycyclic aromatic hydrocarbons (PAHs), which are commonly released from petroleum activities, coal burning, vehicle emissions, and industrial processes.
Several parts of Northeast India—particularly areas affected by oil exploration, coal mining, and urban pollution—face long-term challenges related to oil contamination.
The research team isolated a bacterium called Rhodococcus pyridinivorans C7 from the gut of the earthworm Perionyx excavatus after acclimatising the worms in petroleum-contaminated soil for 60 days.
In laboratory experiments, the bacterium degraded 75% of chrysene within six days, significantly reducing its toxicity.
“Chrysene is a carcinogenic member of USEPA’s priority group of polycyclic aromatic hydrocarbons. We achieved reasonable success in the degradation of chrysene on a laboratory scale. Now we have to scale up and go for field trials,” said Raza R. Hoque, corresponding author of the study.
Nature’s Own Cleanup System
The study highlights how earthworms—often called “ecosystem engineers”—host powerful microbial communities in their gut. When exposed to polluted environments, their gut bacteria adapt and enrich species capable of breaking down harmful hydrocarbons.
Researchers found that pollution conditions increased the abundance of hydrocarbon-degrading bacteria inside the worm’s gut, suggesting that environmental stress naturally selects microbes that can survive and detoxify contaminants.
A Sustainable Alternative
Conventional soil remediation methods, such as chemical oxidation and incineration, are expensive and environmentally disruptive. By contrast, using gut-derived bacteria offers a greener and potentially scalable approach.
For oil- and coal-affected areas of Assam and the wider Northeast, the findings could contribute to future bioremediation strategies tailored to local environmental conditions.
The research was supported by the Department of Biotechnology (DBT), Government of India.
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