Background Nutrients Affect the Biotransformation of Tetracycline by Stenotrophomonas maltophilia as Revealed by Genomics and Proteomics

Certain bacteria are resistant to antibiotics and can even transform antibiotics in the environment. It is unclear how the molecular mechanisms underlying the resistance and biotransformation processes vary under different environmental conditions. The objective of this study is to investigate the molecular mechanisms of tetracycline resistance and biotransformation by Stenotrophomonas maltophilia strain DT1 under various background nutrient conditions. Strain DT1 was exposed to tetracycline for 7 days with four background nutrient conditions: no background (NB), peptone (P), peptone plus citrate (PC), and peptone plus glucose (PG). The biotransformation rate follows the order of PC > P > PG > NB ≈ 0. Genomic analysis showed that strain DT1 contained tet(X1), a gene encoding an FAD-binding monooxygenase, and eight peroxidase genes that could be relevant to tetracycline biotransformation. Quantitative proteomic analyses revealed that nodulation protein transported tetracycline outside of cells; hypoxanthine–guanine phosphoribosyltransferase facilitated the activation of the ribosomal protection proteins to prevent the binding of tetracycline to the ribosome and superoxide dismutase and peroxiredoxin-modified tetracycline molecules. Comparing different nutrient conditions showed that the biotransformation rates of tetracycline were positively correlated with the expression levels of superoxide dismutase.