Genome sequencing of Porostereum spadiceum to study the degradation of levofloxacin.

Despite various plans to rationalize antibiotic use, antibiotic resistance in environmental bacteria is increasing due to the accumulation of antibiotic residues in the environment. This study aimed to test the ability of basidiomycete fungal strains to biotransform the antibiotic levofloxacin, a widely-used third-generation broad-spectrum fluoroquinolone, and to propose enzyme targets potentially involved in this biotransformation. The biotransformation process was performed using fungal strains. Levofloxacin biotransformation reached 100% after 9 days of culture with Porostereum spadiceum BS34. Using genomics and proteomics analyses coupled with activity tests, we showed that P. spadiceum produces several heme-peroxidases together with H 2 O 2 -producing enzymes that could be involved in the antibiotic biotransformation process. Using UV and high-resolution mass spectrometry, we were able to detect five levofloxacin degradation products. Their putative identity based on their MS² fragmentation patterns led to the conclusion that the piperazine moiety was the main target of oxidative modification of levofloxacin by P. spadiceum , leading to a decrease in antibiotic activity. [Display omitted] • Two fungal basidiomycetes were able to biotransform the fluoroquinolone antibiotic levofloxacin. • Porostereum spadiceum was the most efficient fungal strain, biotransforming 50 mg L⁻¹ levofloxacin in 9 days. • Genome sequencing and proteomic analysis highlighted putative enzymes involved in the biotransformation. • Mass spectrometry analysis (LC-MS/MS) revealed the main degradation intermediates of levofloxacin. [ABSTRACT FROM AUTHOR]