Penicillin

Citric acid (CA), uric acid (UA), europium nitrate hexahydrate (Eu(NO₃)₃·6H₂O), nicotinic acid, glucose, D-alanine, L-glutamic acid, L-cysteine and L-leucine were purchased from Aladdin Chemistry Co., Ltd. (Shanghai, China). Antibiotics including oxytetracycline, tetracycline, chlortetracycline, doxycycline, metacycline, minocycline, penicillin, azithromycin, streptomycin, ciprofloxacin and norfloxacin were purchased from Shanghai Macklin Biochemical Co., Ltd. (Shanghai, China). All common metal salts were purchased from Sinopharm Chemical Regents Co., Ltd. (Shanghai, China). HEPES buffer (200 mM) with different pH values was prepared by titrating 200 mM HEPES aqueous solution with 3 M NaOH standard solution. Deionized water (18.2 MΩ cm) prepared from the UPHW-I-90T ultrapure water system was used to prepare standard solutions throughout the experiments. Apparatus and characterization are described in the Supplementary Materials.

The susceptibility of the WT and ΔsdiA mutant strains to different antibiotics was evaluated by the disc diffusion method. The bacterial cells were diluted with PW to 10⁸CFU/mL, and 0.1 mL of bacterial culture was plated onto a TSA plate. The antibiotic resistance was checked against 6 different antibiotics (200 μg/mL and 500 μg/mL): kanamycin, chloramphenicol, rifampicin, erythromycin, tetracycline hydrochloride and penicillin (Macklin Inc., Shanghai, China). Sterilized deionized water was used as a blank control. The sterilized circular filter paper (Φ = 8 mm) was soaked in antibiotic solutions and deionized water for 10 min. Then, the filter papers were removed with sterile tweezers, affixed to a dried TSA plate and incubated for 24 h at 37°C, and the diameter of the antibacterial coil was measured. The tolerance and resistance assay was repeated in three separate experiments. Results are presented as the mean ± SD.