Sulfonamides, as broad-spectrum antibiotics, are widely used to protect against bacterial infections in livestock production. A large number of sulfa antibiotics are discharged into soil and water system, which poses a great threat to the safety of organisms. The antibacterial mechanism of sulfonamides is to prevent folate biosynthesis by competitively inhibiting bacterial dihydropteroate synthetase (DHPS). The inhibitory effect of sulfanilamide on root growth has been reported, but the mechanism has not been determined. Here, we used high performance liquid chromatography with ultraviolet detector (HPLC-UV) and transgenic technology to study the effect of sulfonamides on folate synthesis in plants. The results showed that the application of sulfonamide sharply reduced the content of folic acid in plants, resulting in strong inhibition of cell division in the root apical meristem. The inhibition of sulfonamide on cell division can be relieved by supplementing synthetic folic acid and folinic calcium salt hydrate. The transgenic plants expressing the bacterial antibiotic resistance genes (ARGs) Sul1 or Sul2 showed obvious antibiotic resistance. Taking these results together, we suggest that sulfonamides repress cell proliferation in the root apical meristem by competitively inhibiting the biosynthesis of folic acid in plants.
To reduce the adverse effects of antibiotics and antibiotic resistance genes (ARGs) in the environment, nitrogen-doped biochar (NLBH), derived from lincomycin fermentation dregs (LFD), was employed as an activator in a persulfate (PDS) oxidation system. The system was evaluated for its ability to degrade tetracycline (TC), inactivate antibiotic resistant bacteria (ARB) and remove ARGs. The degradation efficiency of TC in the NLBH/PDS system (70.1%) was higher than that in the pristine biochar/PDS system (10.3%). It was confirmed that the defects and edge pyridinic nitrogen generated in the nitrogen doping process were the reactive sites for PDS activation. According to electron paramagnetic resonance (EPR) and radical quenching experiments, the major mechanism for PDS activation was a non-radical pathway dominated by singlet oxygen ( 1 O 2 ). Radical pathways involving sulfate (SO 4 · - ) and hydroxyl radicals (·OH) were also at play in the NLBH/PDS system, but their role was minor. TC was principally degraded by hydroxylation , demethylation, and decarboxylation , and within 90 min, the NLBH/PDS system effectively inactivated 71.5% of ARB ( Pseudomonas sp. HLS-6). Intracellular ARGs (iARGs; sul 1, sul 2) and intI 1 had log reduction efficiencies of 2.73–4.04 and 2.70, respectively, whereas, extracellular ARGs ( sul 1 and sul 2) and intI 1 accumulated noticeably by 1.52–4.18-and 4.92-log, respectively. This work highlights a promising alternative technique for the removal of antibiotics, ARB and iARGs in future advanced wastewater treatment systems.
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