Hydrological Fluctuations Modulate Potential Plastic-Degrading Microbial Communities in Floodplains

Plastic-degrading (PD) microorganisms play a critical role in mitigating plastic pollution. However, knowledge gaps remain in identifying PD microorganisms in natural systems and understanding the effects of environmental conditions. This study constructed a data set of 120 experimentally confirmed PD sequences and detected potential PD microbes in a seasonal floodplain using metagenomic approaches. The results indicated that putative PD microbes were widely distributed among Pseudomonadota, Bacillota, Chloroflexota, Actinomycetota, and Acidobacteriota. In particular, Acidobacteriota has not yet been experimentally demonstrated to degrade plastics. The predominant PD genes encoded enzymes for biodegradable plastics, such as poly(3-hydroxybutyrate) depolymerase, while putative genes encoding polyethylene terephthalate (PET) hydrolase, mono-(2-hydroxyethyl) terephthalate (MHET) hydrolase, and alkane monooxygenase were also present. Mycobacterium likely contained multiple polyethylene metabolism-related genes, as well as the gene encoding cutinase. Acidobacteriota Gp1-AA17 harbored putative lipA (OLEAN_C07960), encoding a PET hydrolase. Furthermore, putative PD microbes usually exhibited relatively lower abundance and diversity in the flood season compared to the drought season. The PD community was modulated by plastic occurrence, organic carbon, and environmental factors. This study reveals diverse PD potential in floodplains, providing insight into the role of environmental conditions in regulating the PD microbial community.