Heterotrophic nitrification–aerobic denitrification (HN-AD) is an efficient nitrogen removal process and the genus Paracoccus is one important group of the HN-AD bacteria. During an investigation of the microbial diversity in marine ranching of the Pearl River Estuary (PR China), three bacterial strains, designated SCSIO 75817^T, SCSIO 76264^T and SCSIO 80058^T, were isolated from sediments. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the three strains belonged to the genus Paracoccus and their closest neighbors were P. isoporae DSM 22220^T (97.6–98.0%), P. aurantiacus CGMCC 1.13898^T (97.3–97.6%) and P. xiamenensis MCCC 1A16381^T (97.1–97.4%), respectively. The analysis results of 16S rRNA gene similarity, ANI, AAI and dDDH showed that the pairwise similarities between these three strains and their closest neighbors were 97.4–98.5%, 76.9–81.0%, 75.5–79.6% and 20.3–23.3%, respectively. Polyphasic taxonomic data of the phylogenetic, phenotypic and chemotaxonomic analyses indicate that these strains represent three novel species in the genus Paracoccus, for which the names Paracoccus aerodenitrificans sp. nov., Paracoccus sediminicola sp. nov. and Paracoccus albus sp. nov. are proposed, respectively. The study also demonstrated the heterotrophic nitrification–aerobic denitrification (HN-AD) ability of the novel species P. aerodenitrificans SCSIO 75817^T. When it was aerobically cultivated at 28 °C using NH₄⁺-N, NO₃⁻-N and NO₂⁻-N as the sole nitrogen sources, the nitrogen removal efficiencies were 73.4, 55.27 and 49.2%, respectively, and the maximum removal rates were 3.05, 1.82 and 1.63 mg/L/h, respectively. The results suggest that it has promising potential for wastewater treatment.

The escalating crisis of global plastic pollution has prompted increasing efforts toward the identification of plastic-degrading microorganisms as environmentally sustainable solutions. Despite marine ecosystems being the most affected, the systematic exploration of culturable plastic-degrading microorganisms remains critically underexplored. Here, we established the largest marine microbial repository for plastic biodegradation, comprising 1,377 bacterial and 202 fungal strains isolated through optimized culture strategies targeting 13 plastic polymers. Methodological benchmarking revealed selective enrichment combined with carbon-supplemented dual-layer plating as the most effective isolation approach. Plastic substrate specificity drove phylogenetic divergence among degraders, with Bacillus altitudinis emerging as the dominant polyurethane (PU)-degrading lineage. Comprehensive functional screening identified five polyethylene terephthalate (PET)-degrading strains ( Cerrena sp., Hortaea werneckii , Streptomyces badius , Streptomyces cinereoruber , Cladosporium sp.), five polyethylene (PE) degraders ( Qipengyuania citrea , Gordonia mangrovi , Penicillium oxalicum , Penicillium aethiopicum , Streptomyces pluricolorescens ), and 130 polyester-based PU-degrading strains spanning Bacillus , Psychrobacter , Priestia , and Cladosporium genera. This work provides both a foundational microbial resource for plastic biodegradation and establishes a methodological framework for the targeted isolation of plastic-degrading pure cultures. IMPORTANCE: Marine plastic pollution presents a significant global challenge, with millions of tons entering the oceans each year, threatening marine life and ecosystem integrity. Microbial degradation offers a promising, sustainable solution by leveraging natural biological processes to break down plastics. This study makes a substantial contribution to the field by systematically examining 13 plastic types and establishing the largest known marine microbial resource for plastic degradation. Over 1,500 bacterial and fungal strains were isolated from diverse marine environments through optimized culturing strategies. Key microorganisms capable of degrading commonly used plastics—such as polyethylene terephthalate (bottles), polyurethane (foams), and polyethylene (packaging)—were identified. These findings lay a critical foundation for the development of microbial-based technologies to mitigate plastic pollution, offering scalable and environmentally friendly solutions to protect marine ecosystems.

Mangrove ecosystems are critical for coastal protection and biodiversity but are increasingly threatened by plastic pollution, particularly polyethylene terephthalate (PET). In this study, a novel marine bacterium, strain SCSIO 80796 ^T , was isolated from PET debris collected from the mangrove in QiAo Island, Zhuhai, China. Using a polyphasic taxonomic approach, including 16S rRNA gene sequencing, genome-based comparisons (average nucleotide identity [ANI] 72.2%, digital DNA-DNA hybridization [dDDH] 19.0%, average amino acid identity [AAI] 70.6%), and phenotypic and chemotaxonomic analyses, the strain was classified as a novel species within the genus Neptunicella . It is proposed as Neptunicella plasticusilytica sp. nov. (type strain SCSIO 80796ᵀ = MCCC 1K08369 ^T = KCTC 92826 ^T ). Genomic analysis revealed that strain SCSIO 80796ᵀ encodes a novel PET-degrading enzyme, Nm Cut, which degrades PET and yields 105–120 µM of degradation products [terephthalic acid (TPA), mono(2-hydroxyethyl) terephthalate (MHET), bis(2-hydroxyethyl) terephthalate (BHET)] within 48 h at 60°C. Nm Cut exhibits both structural and evolutionary novelty, featuring a unique PET-binding module (PBM) absent in known PETases. PBM is characterized by a long, positively charged α-helix enriched in aromatic residues, forming a distinct substrate-interacting surface with potential as a transferable domain to enhance the efficiency of other plastic-degrading enzymes. This study not only expands the known diversity within Neptunicella but also highlights the potential of marine-derived microbes in addressing plastic pollution through biotechnological applications. IMPORTANCE: The discovery of Neptunicella plasticusilytica sp. nov. advances marine microbial ecology by revealing a novel species in the scarcely studied genus Neptunicella , which previously contained only one cultured representative. Isolated from plastic-polluted mangroves, this bacterium exemplifies microbial adaptation to anthropogenic habitats. Its functional uniqueness is underscored by a phylogenetically distinct polyethylene terephthalate (PET)-degrading enzyme ( Nm Cut), forming an evolutionary clade separate from all known plastic-degrading enzymes. By integrating taxonomic discovery with functional genomics, this study bridges the gap between microbial diversity and biotechnological potential. The dual novelty of N. plasticusilytica —as a taxonomic addition and a source of evolutionarily unique enzymes—highlights the importance of exploring understudied environments to address global challenges like plastic pollution.