Effects of tetracycline exposure on microbial community structure, functions, and assembly in coastal bay sediments:...

Bacteria have a crucial role in the biogeochemical cycles of coastal bay ecosystems. However, Our understanding of the dynamic succession and interaction of bacterial communities under tetracycline (TC) stress is still lacking. In this research, we employed 16S rRNA gene amplification sequencing, network analysis, and normalized stochasticity ratio analysis (NST) to analyze the dynamic changes and assembly processes of bacterial communities and their functions in coastal bay sediments under different TC concentrations over exposure time. The results indicated that the variation in diversity, structure, and taxonomic composition of bacterial communities was more strongly influenced by exposure time than by changes in concentration. The diversity of the bacterial community increased linearly with exposure time. Moreover, as exposure time increased, the functional capabilities of the bacterial community underwent significant changes. The community structure became more complex, with the 30-day network exhibiting the highest number of nodes, the highest average degree (Avgk), greater graph density (GD), and the lowest average path length. Robustness analysis showed that upon removal of certain nodes, the 30-day network maintained relatively high connectivity, indicating greater structural stability of the bacterial community at this stage. Additionally, the NST results suggested that the bacterial community assembly process shifted from deterministic to stochastic. These findings offer valuable insights for future research on microbial diversity in ecosystems under pollutant exposure.