A metagenomic analysis of soil and rhizosphere samples from the Antarctic vascular plants Deschampsia antarctica and Colobanthus quitensis is conducted, as sources of microbial enzymes with potential PET-hydrolytic activity, demonstrating the diversity of PET-hydrolase-like genes within Antarctic rhizosphere and soil microbiomes.
Abstract
Polyethylene terephthalate (PET) is a persistent synthetic polymer that is increasingly detected in terrestrial environments, where it influences soil microbial activity and carbon cycling. Microorganisms capable of hydrolyzing PET and related polyesters constitute a valuable enzymatic resource for developing low-temperature biocatalysts and for advancing the understanding of soil functional adaptation to plastic pollution. Here, we conducted a metagenomic analysis of soil and rhizosphere samples from the Antarctic vascular plants Deschampsia antarctica and Colobanthus quitensis, as sources of microbial enzymes with potential PET-hydrolytic activity. Hidden Markov Models constructed from experimentally validated PET hydrolases identified 152 putative PET hydrolases (pPETHs) spanning multiple protein families. Four candidates exhibited amino acid motifs characteristic of Ideonella sakaiensis PETase, including the conserved alpha/beta hydrolase fold and the Ser-His-Asp catalytic triad. One candidate from a Duganella genome also contained a tryptophan residue associated with efficient product release during PET hydrolysis. Molecular docking and molecular dynamics analyses revealed that candidates retain the core catalytic architecture of established PET hydrolases, while simultaneously displaying structural signatures of cold adaptation. These findings demonstrate the diversity of PET-hydrolase-like genes within Antarctic rhizosphere and soil microbiomes, broadening the current understanding of microbial enzymatic potential under cold, oligotrophic conditions. The identified sequences highlight the rhizosphere as a reservoir of functional diversity relevant to soil biotechnology, cold-adapted catalysis, and microbial strategies for transforming recalcitrant carbon substrates.
ABSTRACT Polyethylene terephthalate (PET) waste represents a major environmental challenge due to limited recycling solutions. Thermophilic bacteria from geothermal environments harbor diverse enzymatic machinery adapted to extreme conditions, offering promising biocatalysts for plastic degradation; however, biological resources from Peru and other South American countries remain scarce. We characterized four bacterial strains isolated from two geothermal sites in Cajamarca, Peru, screened for PET hydrolysis at 50°C. Whole‐genome sequencing using hybrid assembly achieved near‐complete circular genomes. GTDB‐Tk classification identified three species: Neobacillus thermocopriae (strain 19A), Bacillus licheniformis (strains 16P and BI2), and Brevibacillus agri (strain BI8). Quantitative assays revealed that strain 16P achieved the highest mass loss (0.598%), followed by strain BI8 (0.449%). ATR‐FTIR analysis of the incubated sheets showed a significant reduction of the ester carbonyl index in strains 16P, 19A, and BI8 relative to both non‐incubated PET and an abiotic control, whereas strain BI2 did not differ from the controls, indicating preferential modification of ester bonds at the sheet surface. Genome mining and structure‐based homology searches identified multiple candidate enzymes similar to validated PETases and carboxylesterases, including PETase46‐like homologs in strains BI8 and 16P and a terephthalate‐active carboxylesterase homolog in strain 16P. Molecular docking supported the conservation of catalytic geometry and substrate‐binding sites in these candidates. This work represents one of the first systematic genomic and structural characterizations of putative PET‐hydrolases in Peruvian geothermal bacteria, expanding knowledge of extremophile diversity and advancing thermostable enzymes for sustainable plastic waste management.
Marco A Rivera-Jacinto, Claudia Rodríguez-Ulloa, Sara R Briones-Ramírez et al.· MicrobiologyOpen· 0 citations
A targeted mining workflow is developed that screens exclusively plastic-associated datasets through multi-step bioinformatic filtering—integrating catalytic-motif screening, disulfide-topology validation, structural-similarity scoring, and phylogenetic profiling—to recover high-confidence PETase candidates, resulting in a thermostable enzyme that depolymerizes PET across a broad temperature range.
Konstantinos Rigkos, Dimitra S Bezantakou, Kyriakos Antoniadis et al.· bioRxiv· 0 citations
The long-term accumulation of polyethylene terephthalate (PET) in marine environments may drive the evolution of microbial degradation capabilities, positioning the ocean as a valuable reservoir for discovering novel PET-degrading microorganisms. In this study, we isolated 305 marine-derived microorganisms with potential PET-degrading capability from samples collected from mangrove areas of Zhanjiang and the intertidal zones of Daya Bay, Shenzhen, China, using PET powder as a major carbon source. Subsequent evaluation of degradation performance via scanning electron microscopy and Fourier-transform infrared spectroscopy analysis identified 14 isolates capable of degrading PET film. These 14 strains belonged to 14 distinct species, none of which, to the best of our knowledge, has been previously documented as PET degraders. Among them, Microbacterium aurum SCSIO 85700 exhibited the most potent PET-degrading activity, achieving a weight loss of 2.1 mg (2.1%) and a 6.5% increase in relative crystallinity over 30 days. Genome analysis revealed the genetic basis underlying PET degradation and associated metabolic pathways in strain SCSIO 85700. Notably, genome mining and structural modeling identified two candidate polyester hydrolases, MA2267 and MA2443, possessing conserved His–Asp–Ser catalytic triads and exposed substrate-binding clefts resembling those of characterized PET-degrading enzymes, suggesting their potential involvement in PET depolymerization. Collectively, this study expands the recognized diversity of marine PET-degrading microorganisms and provides microbial resources for sustainable PET bioremediation.
Shijing Deng, Qiaoqiao Guo, Yunhe An et al.· Microorganisms· 0 citations
Cellulases are crucial for converting biomass into renewable energy. Despite extensive research, there remains a significant industrial demand for novel cellulases, particularly those with multi-substrates catalytic activity. This study aimed to identify and characterize a novel cellulase from a high-altitude soil metagenome library using functional screening method. A novel 1218-bp GH6 family hydrolase gene, designated zfy1641, was identified from a Mount Everest soil library. Bioinformatics analysis indicated that it encoded a 405-amino-acid protein (43.7 kDa) and was classified into glycoside hydrolase family 6 (GH6). The target glycoside hydrolase gene was cloned and heterologously expressed, then the recombinant protein was purified, and its biochemical properties and kinetic parameters were characterized. The purified recombinant enzyme exhibited broad substrate specificity, demonstrating significant activity against carboxymethyl cellulose (CMC-Na; 69.87 ± 0.13 U/mg), locust bean gum (125.56 ± 0.18 U/mg) and chitin (77.06 ± 0.08 U/mg). ZFY1641 represented a novel member of the GH6 family, that exhibited detectable reducing sugar release from chitin-a function not previously documented for this family. Moreover, ZFY1641 demonstrated optimal activity at 50°C and pH 5.0, and exhibited moderate thermal stability, tolerance to selected metal ions, and halophilicity under the conditions tested. These characteristics suggest potential utility of ZFY1641 in industrial processes, though further validation is required. This work expanded the substrate diversity of GH6 family enzymes and provided a foundation for the development of new enzymatic preparations with a novel multi-functional GH6 family enzyme.
Y. Lyu, Shenghong Wu, Xinyu Fan et al.· Carbohydrate Research· 0 citations
The “Motif‐to‐Market” framework is proposed, using the M5 motif as a fingerprint to curate functional PETases for efficiency and stability, with distinct pathways for industrial and marine applications.
A wide range of microorganisms produce storage biopolymer polyhydroxyalkanoates (sPHAs) as carbon and energy reserves. However, only bacteria and fungi are known to degrade microbial sPHAs, using enzymes called polyhydroxyalkanoate depolymerases (PHADs). Here we show that some animals also have PHADs that can degrade sPHAs. We discovered a PHAD in the gutless oligochaete Olavius algarvensis, a marine worm that gains nutrition by digesting bacterial symbionts, including a dominant symbiont in which sPHAs account for up to 42% of cellular carbon stores. Enzyme assays, combined with mass spectrometry, confirmed that heterologously expressed O. algarvensis PHAD degraded sPHAs into hydroxyalkanoate monomers that can enter conserved metabolic pathways. Imaging of mRNA showed that PHAD was expressed in the oligochaete epidermis, the site of symbiont digestion. We further identified PHADs in more than 66 gut-bearing animal species from nine phyla and 19 protist species from three major supergroups, suggesting that the last common ancestor of metazoans possessed PHADs. Functional assays confirmed that PHADs from phylogenetically distant animal lineages spanning aquatic and terrestrial environments degrade sPHAs. These findings reveal a previously unrecognized pathway by which protists and animals can access microbial carbon reserves, with broad relevance given the widespread occurrence of sPHAs across ecosystems.
Caroline Zeidler, Harald R Gruber-Vodicka, D. Michellod et al.· Nature Ecology & Evolution· 0 citations