Assessing the biodegradation efficiency and underlying molecular pathway of strain AEPI 0-0: a newly isolated tetracycline-degrading Serratia marcescens

With the development of aquaculture and animal husbandry, the use of tetracycline antibiotics (TCs) has increased, thereby leading to negative impacts on naturally-occurring microbial communities. Microbial degradation is an effective and environmental friendly method to degrade TCs, but so far, very few cultured strains are suitable for this purpose. In this study, a bacterial strain, AEPI 0-0, with the potential to degrade TCs was isolated, with phylogenetic analysis subsequently classifying it as Serratia marcescens. The single factors that affected the strain’s degradation efficiency on TC-HCl were then studied using an orthogonal experimental design. The results showed that the biodegradation efficiency could reach about 85% on the 4th day, with the process following the degradation kinetic equation. Subsequently, RNA-seq was used and the differentially expressed genes（DEGs）were annotated and analyzed. The results showed that more genes were enriched in biological processes such as amino acid metabolism, carbohydrate metabolism, and cell membrane transport metabolism pathway. In addition, TetR family transcription factors may play an important role in the physiological process of AEPI 0-0 tolerance and degradation of tetracycline. In conclusion, a Serratia marcescens strain with high potential for TCs degradation was obtained, with the conditions for maximum degradation efficiency subsequently optimized, changes in the metabolic pathways were also preliminarily discussed. This strain could potentially be applied for the bioremediation of soil and water contaminated by TCs antibiotics. At the same time, this study also provides strains as well as theoretical support for microbial-based remediation of the environment.