Microbes, Plastics, and Antibiotic Resistance: Insights from the Sundarbans

Context

A study by the Indian Institute of Science Education and Research (IISER), Kolkata, published in FEMS Microbiology Letters, has highlighted a dual role of microbes found in the Sundarbans. While some microbes possess the ability to degrade plastics, they also act as reservoirs of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs), raising concerns for public health and the environment.

---

Key Findings

1. Plastic Persistence and Microplastics

   • Plastics degrade into microplastics (<5 mm) and nanoplastics (<1 μm).

   • These particles accumulate in ecosystems, attract pollutants (heavy metals, antibiotics), and provide surfaces for microbial colonisation.

2. Study Site & Method

   • Location: Mooriganga estuary, Sundarbans (receives ~3 billion microplastic particles daily).

   • Samples: Surface water collected monthly (2020–21).

   • Technique: Metagenomic sequencing of microbial DNA.

   • Databases: PlasticDB for plastic-degrading enzymes (PDEs), plus ARGs, MRGs, and mobile genetic elements databases.

3. Plastic-Degrading Enzymes (PDEs)

   • Found 838 PDE hits, acting on 17 different plastic polymers.

   • Most abundant: enzymes breaking down polyethylene glycol (PEG) (biomedical + industrial contamination source).

   • PDEs more abundant during monsoon (due to nutrient and plastic influx).

4. Antibiotic and Metal Resistance Genes

   • Co-occurrence of PDEs + ARGs + MRGs within same microbial communities.

   • Common ARGs: resistance to aminoglycosides.

   • Common MRGs: resistance to zinc.

   • Strong link between plastic exposure and the rise of microbial resistance traits.

---

Significance

• Positive:

  • Demonstrates natural microbial adaptation to degrade plastics.

  • Offers potential for biotechnological innovations in tackling plastic waste.

• Negative:

  • Plastic-degrading microbes may simultaneously spread antimicrobial resistance (AMR).

  • Plastics serve as “hotbeds” for gene exchange, enabling horizontal gene transfer.

  • Risk of worsening AMR, undermining One Health and public health goals.

---

Broader Concerns

1. Climate Change Factor

   • Climate-induced floods, temperature shifts, and salinity may accelerate gene transfer.

   • Raises the possibility of ARGs spreading into human pathogens.

2. One Health Implication

   • Direct link between environmental pollution, microbial adaptation, and human health.

   • Highlights interconnection of environment, animals, and humans in AMR spread.

3. Policy Implications

   • Need for integrated plastic waste management.

   • Careful risk assessment before deploying plastic-degrading microbes at scale.

   • Strengthening India’s AMR surveillance framework.

---

Prelims Pointers

• PETase enzyme: Discovered in Ideonella sakaiensis, breaks down PET (plastic bottles).

• One Health Concept: Integrates human, animal, and environmental health.

• Metagenomics: Technique to sequence DNA of entire microbial communities.

• Sundarbans: Largest mangrove forest, receives ~3 billion microplastic particles daily.

---

Mains Practice Questions

1. GS-III (Environment)
   “Plastic-degrading microbes offer promise for waste management but may exacerbate antimicrobial resistance (AMR). Critically examine in the context of recent IISER Kolkata findings.”

2. GS-III (Science & Tech + Health)
   “Discuss the significance of microbial biodegradation of plastics in India. How can the risks of antimicrobial resistance be mitigated while pursuing such solutions?”

3. GS-II / Essay
   “Plastic pollution and antimicrobial resistance are twin crises with shared roots in human activity. Evaluate this statement in the context of ‘One Health’.”