Succession-driven potential functional shifts in microbial communities in the tire-plastisphere: Comparison of pristine and scrap tire.

Tire microplastics (TMPs) represent a major contributor to microplastic pollution, posing threats to aquatic ecosystems. As carbon-rich substrates, TMPs influence microbial colonization and ecological functions. This study investigates the impacts of pristine (P-TMPs) and scrap (S-TMPs) TMPs from the same brand on microbial communities within the tire-plastisphere. We incubated wood particles, P-TMPs, and S-TMPs in situ in a lake environment for 60 days. Utilizing amplicon and metagenome sequencing, we analyzed structural and potential functional changes in microbial communities across five colonization time points. Our findings reveal that TMPs establish distinct ecological niches, functioning as hotspots of microbial activity in aquatic environments. Both niche specificity and colonization time significantly shape microbial community structure. During the early adaptation stage, we observed clustering patterns in both microbial composition and functional genes associated with the particles. Over time, divergent succession in community composition and potential function emerged, primarily driven by differences in substrate availability between niches. Notably, the substrate availability of S-TMPs promoted microbial community shifts, whereas the P-TMPs posed challenges to microbial adaptation. This study elucidates the long-term adaptive processes exhibited by microbial communities when colonizing the contrasting ecological niches represented by these two TMP states (pristine vs. scrap), documenting the progression from community structural change to functional adaptation. The results underscore the complexity of TMP impacts on microbial ecology and highlight the critical need for long-term monitoring to fully understand their environmental implications.