Functional and Genomic Insight into Plastic-Degrading Potential of Cladosporium Fungi Associated with the Marine Copepod Acartia tonsa

Plastic pollution poses a severe environmental challenge in marine ecosystems, which could be addressed by plastic-degrading microorganisms. In previous studies, five fungal strains of the genus Cladosporium, isolated from the marine copepod Acartia tonsa, showed potential plastic polymer degradation activity. This study provides genomic and functional evidence of the metabolic activities of copepod-associated Cladosporium strains involved in polymer biodegradation. Five Cladosporium strains were tested for their ability to degrade poly(butylene succinate-co-adipate) (PBSA), poly(1,4-butylene adipate-co-terephthalate) (PBAT), and low-density polyethylene (LDPE) emulsions. These polymers are among the most used worldwide and contribute to plastic pollution. Whole-genome sequencing and functional annotation were conducted to elucidate the mechanisms of polymer degradation. Fungal activity was polymer dependent: the average sizes of zones of clearance were 40.6, 28.5, and 11.4 cm2 for PBSA, PBAT, and LDPE, respectively. Up to 35 different genes putatively associated with polymer degradation were found in all fungal strains. Most of them are shared among all tested strains, with few genes unique to each strain. Predicted gene content and putative fungal activity varied among strains and showed patterns coinciding with taxonomic grouping. Results provide additional evidence of the effectiveness of Cladosporium strains for plastic degradation. This aspect holds significance for the implementation of effective bioremediation strategies to counter marine plastic pollution.