Screening salt-tolerant bacteria for enhanced antibiotic degradation in mangrove ecosystems

Abstract

In recent years, widespread antibiotic use has led to frequent occurrences of antibiotic misuse and drug resistance. Tetracyclines, sulfonamides and quinolones are commonly used in marine aquaculture, resulting in significant antibiotic residues in wastewater due to their persistent characteristics. As emerging pollutants, antibiotics pose serious risks to human health and ecosystems. This study investigates salt-tolerant bacteria capable of degrading multiple antibiotics in mangrove ecosystems. Using an enrichment method with antibiotics as the sole carbon source, bacterial strains were screened and acclimated to salinity conditions, then identified through 16S rDNA sequencing and morphological observation. The antibiotic degradation rate by bacterial strains was determined by High- Performance Liquid Chromatography. The results showed that 37 strains of bacteria were screened, predominantly Bacillus sp., Pseudomonas sp. and Herbaspirillum sp. The optimum growth conditions for selected strains were determined as pH 7.0, temperature = 30℃, and liquid volume of 100 mL in a 250 mL flask. The salinity acclimation of dominant strains can be from 3.4‰ to 34.0‰. The strains exhibited high tolerance concentrations for tetracyclines (up to 150 mg/L), sulfonamides, and quinolones (up to 300 mg/L each). Average degradation rates exceeded 83% for tetracyclines and quinolones, and 60% for sulfonamides. These salt-tolerant bacteria strains from mangrove ecosystems show promise for mariculture wastewater treatment, providing valuable biological resources for antibiotic degradation.