Gentamicin

E. coli DH10B (Invitrogen, Waltham, MA) was used for plasmid cloning and recombinant protein expression. LB media (BD-Difco, Franklin Lakes, NJ) was utilized as the culture media. The working antibiotic concentrations were as follows: 50 μg/mL chloramphenicol (Daejung Chemicals, Siheung, Republic of Korea) and 50 μg/mL gentamicin (KisanBio, Seoul, Republic of Korea). Primers used in this study were synthesized and purchased from Macrogen (Seoul, Republic of Korea). AzF (Chem-Impex, Wood Dale, IL), a non-canonical amino acid, was included as a substrate for aaRS. Arabinose (Alfa Aesar, Haverhill, MA) and isopropyl β-d-1-thiogalactopyranoside (IPTG, Bioneer, Daejeon, Republic of Korea) were applied as inducers.

Antibiotic susceptibility of the Lpb. plantarum strains was investigated as described previously [19 (link)]. A total of 13 antibiotics were used to evaluate antibiotic resistance: ampicillin (AMP; 10 μg), chloramphenicol (C; 30 μg), clindamycin (CD; 10 μg), ciprofloxacin (CIP; 5 μg), gentamicin (CN; 10 μg), doxycycline (DXT; 30 μg), erythromycin (E; 15 μg), kanamycin (K; 30 μg), penicillin G (P; 10 IU), streptomycin (S; 10 μg), trimethoprim-sulfamethoxazole (SXT; 25 μg), tetracycline (TE; 30 μg), and vancomycin (VA; 30 μg) (KisanBio, Seoul, Korea). Each Lpb. plantarum strain (1 × 10⁷ CFU/mL; 100 μL) was spread onto MRS agar plates, and antibiotic discs were placed on the plates. After incubation at 37 °C for 24 h, the diameter of the inhibition zone was measured. The results were presented according to the Clinical and Laboratory Standards Institute 2012 standards [20 ].