Identification and characterization of two novel Acinetobacter species capable of degrading polyester

The ubiquitous presence of Acinetobacter species in the environment holds significant biotechnology potential, particularly in the degradation of various pollutants. In this study, we characterize two plastic-degrading bacteria, strains CAAS 2-6 and CAAS 2-13, isolated from landfill leachate and a strawberry farmland, respectively. Strain CAAS 2-6 showed the highest 16S rRNA sequence similarity (97.7%) with Acinetobacter gerneri DSM 14967T, while strain CAAS 2-13 was most closely related (99.6%) to Acinetobacter kanungonis PS-1T. Phylogenetic analysis of 16S rRNA and gyrB-rpoB genes placed both strains on distinct branches. Genomic comparisons revealed the highest digital DNA-DNA hybridization/average nucleotide identity values for CAAS 2-6 with Acinetobacter indicus CIP 110367T (22.7%/77.0%) and for strain CAAS 2-13 with A. kanungonis PS-1T (66.5%/96.0%). Based on phenotypic and chemotaxonomic data, we propose strain CAAS 2-6T as the novel species Acinetobacter minutum sp. nov. (type strain CAAS 2-6T = GDMCC 1.3951T = JCM 36321T = KCTC 8156T), and strain CAAS 2-13T as the novel subspecies A. kanungonis subsp. fragariae subsp. nov. (strain CAAS 2-13T = GDMCC 1.3956T = JCM 36322T = KCTC 8157T). Both strains utilized polylactic acid, polybutylene succinate-adipic acid (PBSA), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), and polybutylene terephthalate as sole carbon sources, with CAAS 2-6 exhibiting superior growth on PBSA, PBS, and PBAT. Genomic annotation identified genes encoding plastic-degrading enzymes multicopper oxidase AbMCO and alkane hydroxylase AlkB. Enzymatic depolymerization assays confirmed in vitro production of plastic monomers. These findings expand the known metabolic capabilities of Acinetobacter and provide promising new candidates for plastic bioremediation.IMPORTANCEAcinetobacter spp. demonstrate significant potential for the bioremediation of environmental pollutants. This study discovers and characterizes two novel Acinetobacter strains, CAAS 2-6T (A. minutum sp. nov.) and new subspecies CAAS 2-13T (A. kanungonis subsp. fragariae subsp. nov.), which exhibit a remarkable capacity to utilize five major commercial polyesters (polylactic acid, polybutylene adipate terephthalate, polybutylene terephthalate, polybutylene succinate, and polybutylene succinate-adipic acid) as sole carbon sources. Genomic and enzymatic analyses identified a multicopper oxidase (AbMCO) and an alkane hydroxylase (AlkB) as key biocatalysts in the depolymerization process. Our work: (i) significantly expands the known diversity of plastic-degrading Acinetobacter, (ii) provides novel enzyme candidates and genomic resources for biocatalyst development, and (iii) supplies engineerable microbial chassis for synthetic biology applications in waste bioconversion.