Molecular mechanism underlying the degradation of tetracycline by Apiotrichum loubieri MFZ-16

Microbial degradation of tetracycline (TC) is promising owing to its high efficiency and low price; however, a thorough knowledge of its biotransformation is still lacking. In this study, we isolated a novel TC-degrading strain, Apiotrichum loubieri MFZ-16, from kennel soils. Response surface model analysis showed that MFZ-16 degraded TC by 97.93% at 34.54 ℃, pH 5.06%, and 12.93% inoculation. Liquid chromatography-mass spectrometry and principal component analyses revealed significant differences in metabolites between TC-salt media with and without MFZ-16. Furthermore, eight key intermediates of TC degradation were identified and their reaction processes were predicted. Transcriptome analysis revealed that MFZ-16 contained 137 functional genes involved in TC biodegradation. Three TC metabolic pathways, namely, the tyrosine, tryptophan, and D-glucose 1-phosphate metabolic pathways, were predicted, and the tyrosine and tryptophan metabolic pathways were predicted for the first time. These results suggest that A. loubieri strain MFZ-16 is an efficient and promising microbe for TC bioremediation. These findings would give a new insight into the mechanism of TC degradation.