Functional and genomic insights into landfill-isolated Brucella intermedia strains capable of degrading Linear Low-Density Polyethylene (LLDPE)

The global accumulation of linear low-density polyethylene (LLDPE) waste has created an urgent need for sustainable biodegradation strategies. Here, we report the identification and characterization of two Brucella intermedia isolates that can degrade LLDPE. Soil samples were collected from the Matuail landfill in Dhaka, Bangladesh, and screened on minimal salt medium supplemented with LLDPE. Both isolates demonstrated growth capacity under carbon-limited conditions, with LLPDE polymer being the sole carbon source. LLDPE polymer samples recovered from bacterial cultures showed extensive chemical and physical alterations as evidenced by Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively. FTIR spectroscopy analysis of bacteria-incubated plastic sheets showed the formation of new carbonyl, hydroxyl, and ester functional groups consistent with oxidative degradation of plastics. SEM confirmed surface erosion and cracking. Whole-genome sequencing identified both isolates as closely related but distinct strains of Brucella intermedia (ANI > 99.5%), enriched in enzymes associated with oxidative activation (copper oxidase), depolymerization (polyesterase, PLA depolymerase, polyamidase), and assimilation-mineralization (3-hydroxyvalerate dehydrogenase). Comparative resistome profiling revealed a stable, efflux-dominated resistance mechanism with RND-type and SMR transporters. Both landfill isolates lacked homologs to known virulence factors, suggesting minimal pathogenic potential. Both isolates exhibited hydrocarbon-induced biofilm formation, supported by the presence of adhesion and exopolysaccharide biosynthesis genes. Collectively, these findings identify environmental B. intermedia strains as low-risk, ecologically adapted bacteria capable of LLDPE degradation. This work expands our understanding of plastic-degrading microbes and reveals genomic insights into Brucella-mediated LLDPE degradation, advancing our repertoire in plastic bioremediation.