The microbial community composition and diversity were analyzed using archaeal, bacterial, and eukaryotic 16S/18S rRNA gene sequencing. This approach enabled a detailed analysis of the microbial community within each inoculum during the extended CO conversion enrichment process and across different reactor positions. A heat map at the genus level, along with α-diversity measures, was generated to visualize taxonomic distribution across samples, highlighting key genera and their spatial distribution within the reactor system (Figure ). Further analysis revealed that microbial diversity in the R1 was lower than in the R2 and R3, aligning with the higher CO conversion efficiency observed in R1. This difference may be attributed to the characteristics of both AD and CM as inoculum, as the complexity of each of them appears to foster greater microbial diversity within TBRs compared to AS.