The enrichment of nitrogen-fixing bacteria on biodegradable plastics during the early stage of degradation under agricultural soil conditions and changing climate

• Sphingomonas, Hymenobacter, Massilia, Methylobacterium-Methylorubrum are dominant. • These diazotrophic bacteria are almost absent in the initial soils. • These diazotrophic bacteria are reported to be involved in plastic degradation. • No effects of agricultural practices or climate were observed on N-fixing bacteria. To address the issue of plastic pollution, biodegradable plastics have been developed as an alternative to conventional non-biodegradable plastics. N-fixing bacteria have been shown to play a pivotal role in the microbial degradation of biodegradable plastics. However, little is known about how N-fixing bacteria respond to plastic degradation in agricultural practice. Therefore, this study aimed to (i) provide insights into the N-fixing bacteria associated with biodegradable plastics during the early stage of degradation (after 60 days of exposure), and (ii) examine the impact of agricultural practices and climate simulations on the enrichment of N-fixing bacteria across various plastic types: poly(butylene succinate) (PBS), polybutylene adipate terephthalate (PBAT), and polyethylene (PE) as a reference. Our findings revealed that N-fixing bacterial genera, particularly Sphingomonas, Hymenobacter, Massilia , and Methylobacterium - Methylorubrum , outcompete other N-fixing bacteria in the plastisphere at the early degradation stage, while they are almost absent in the initial soils. These bacterial groups have been previously linked to plastic degradation and the production of plastic-degrading enzymes. Moreover, our results indicate that agricultural practices and climate conditions did not significantly affect the enrichment of N-fixing bacteria. Instead, this study explored the enrichment of these bacteria on biodegradable plastics, particularly PBAT and PBS, under changing climate and land use conditions during the early degradation phase. Additionally, we identified soil-associated minor N-fixing bacteria that dominate these N-poor plastics in both conventional and organic farming systems. Identifying plastic-preferring microbial groups is crucial for understanding the microbial plastic degradation process under the real world’s scenario.