Functional Microbial Analysis of Oxytetracycline Wastewater Treatment Plant

This study aimed to investigate the relationship between microbial community dynamics and pollutant removal performance by analyzing microbial community composition at four seasonal operational stages (T1-T4). High-throughput 16S rRNA sequencing was employed to characterize the microbial structure of the system and to explore how microbial succession under long-term operation and antibiotic stress may relate to organic matter degradation, nitrogen transformation, and antibiotic tolerance. The results showed that several phyla, including Bacteroidota, Proteobacteria, Verrucomicrobiota, Chloroflexi, Firmicutes, and Actinobacteriota, remained dominant throughout the operational periods, indicating a relatively stable core microbial community. These taxa are commonly associated with key ecological functions in wastewater treatment systems, such as macromolecular organic matter degradation, nitrification-denitrification processes, and environmental adaptation under stress conditions.At the genus level, several key taxa related to nitrogen cycling and environmental resilience were identified, including Thauera, OLB8, Limnobacter, and Truepera, which were consistently detected across different operational stages. These genera are frequently reported as denitrifying or nitrate-reducing bacteria and may contribute to nitrite accumulation and denitrification processes in the system. In addition, the occurrence of stage-specific genera such as Nitrosomonas, Pseudomonas, and Ottowia suggests that microbial community succession occurred in response to environmental fluctuations, potentially influencing nitrogen transformation pathways and overall pollutant removal efficiency. Some taxa also demonstrated tolerance to antibiotic stress, indicating their possible role in maintaining microbial stability under oxytetracycline (OTC) exposure.Overall, this study links microbial community structure with reactor performance and provides ecological insight into the functioning of biological treatment systems treating antibiotic-containing wastewater. Understanding the composition and succession of microbial communities helps elucidate the mechanisms supporting organic matter degradation, nitrogen removal, and system resilience under antibiotic pressure. It should be noted, however, that the functional interpretations presented in this study are primarily inferred from taxonomic affiliation and previously reported ecological roles, and further validation using functional gene analysis or metagenomic approaches would be necessary to confirm the specific metabolic activities of these microorganisms.