New research reveals that bacteria living in your digestive tract possess natural weapons to combat the growing threat of ingested microplastics

The silent invasion of plastic particles into the human body has reached an alarming scale. From the food we consume to the water we drink, microscopic fragments of synthetic polymers penetrate our digestive systems daily. Yet recent discoveries reveal an unexpected defender lurking within us. The human gut microbiome harbors specialized bacteria equipped with enzymes capable of breaking down these persistent pollutants. This finding transforms our understanding of how the body responds to environmental contamination and opens new pathways for addressing one of modern society’s most pressing health challenges.​

Scientists have identified HGMP01, a novel enzyme from the human gut metagenome that demonstrates remarkable ability to hydrolyze polyethylene terephthalate nanoparticles. This protein operates efficiently at body temperature of 37°C and functions across a broad pH range from 7.0 to 11.0, with peak activity under mildly alkaline conditions. The discovery emerged from systematic screening of gut bacterial genomes, revealing over 22,000 homologous sequences potentially encoding PET hydrolases in cultivated healthy human gut bacteria. These enzymes employ a conserved serine-histidine-aspartate catalytic triad mechanism, attacking ester bonds within the polymer structure through nucleophilic hydrolysis.​

The implications extend beyond biochemical curiosity. Patients with inflammatory bowel disease show significantly elevated microplastic concentrations in fecal samples compared to healthy individuals, with IBD patients exhibiting 41.8 items per gram versus 28.0 items per gram in controls. Polyethylene terephthalate and polyamide dominate the detected polymers, correlating with disease severity. This pattern suggests that either chronic inflammation impairs plastic clearance mechanisms or that sustained microplastic exposure exacerbates intestinal dysfunction through disruption of microbial communities and barrier integrity.​

Evidence for active plastic degradation within the digestive tract continues to mount. Simulated gastrointestinal digestion studies demonstrate that PET microplastics undergo structural biotransformation during colonic transit, appearing markedly different from their original form. The gut microbiota responds dynamically to plastic exposure, with certain bacterial families like Enterobacter, Holdemanella, and Weizmannia showing both elevated abundance and associated PET hydrolase activity. These microorganisms may adhere to microplastic surfaces, forming biofilms that facilitate degradation processes. The enzymatic breakdown generates intermediate products including mono(2-hydroxyethyl) terephthalic acid and terephthalic acid, compounds that potentially integrate into existing metabolic pathways.​

The temperature and pH stability of HGMP01 proves particularly significant for physiological relevance. While many environmental PET degrading enzymes require elevated temperatures near the polymer’s glass transition point of 65 to 80°C, HGMP01 maintains considerable activity at human body temperature. Its tolerance for alkaline conditions aligns with pH variations encountered in different intestinal segments, suggesting evolutionary adaptation to the gut environment. Concentration dependent effects show proportional increases in hydrolysis products with ascending enzyme levels from 50 to 2000 nanomolar, indicating substantial degradation potential when sufficient enzyme is present.​

The broader health implications remain under investigation. Microplastic exposure alters gut microbiome composition, decreasing beneficial genera while promoting pathogenic species expansion. These shifts trigger inflammatory responses, compromise intestinal barrier function, and modify metabolic outputs including short chain fatty acid production. Microbial composition changes associated with microplastic treatment resemble patterns previously linked to depression and colorectal cancer, though direct causal relationships require further study. The interaction between microplastics and gut bacteria creates bidirectional effects where plastics alter microbial ecology while microbes simultaneously attempt degradation.​

Moving forward, this discovery positions the gut microbiome as both victim and potential solution to plastic contamination. The natural presence of PET hydrolyzing capacity in intestinal bacteria suggests evolutionary pressure from environmental exposure. While current enzymatic activity remains lower than engineered variants from environmental sources, these gut resident enzymes operate under physiological conditions without requiring external intervention. Understanding these endogenous degradation mechanisms could inform therapeutic strategies ranging from probiotic formulations to enzyme supplementation for reducing microplastic burden and associated health risks.​