Bacterial community structures and biodegradation kinetic of Tiamulin antibiotic degrading enriched consortia from swine wastewater

The antibiotic tiamulin (TIA) is common and widely used medication for dysentery eradication in swine productions. Tiamulin persists in livestock manure, and its residues have been found in various environment. This work obtained four tiamulin-degrading enriched bacterial consortia from a covered anaerobic lagoon system and a stabilized pond system of swine farms. Tiamulin was efficiently removed by the enriched cultures at the concentrations between 2.5 and 200 mg/L, with a removal of 60.1-99.9% during 16 h and a degradation half-life of 4.5-15.7 h. The stabilized pond system cultured with taimulin solely could eliminate tiamulin at the highest rates. The logistic substrate degradation model fit most of the experimental data. Next-generation amplicon sequencing was conducted, and it was found that the bacterial community was significantly impacted by the inoculum source, nutrient addition, and high tiamulin concentrations. Principal coordinate analysis (PCoA) indicated the similarity of bacterial communities in the original enriched samples and the 2.5 mg/L tiamulin-removed cultures. The 200 mg/L consortia were rather different and became similar to the other 200 mg/L consortia from different sources and cultures without nutrient supplementation. Shannon and Simpson indices suggested a reduction in bacterial diversity at high concentrations. The microbes that had high growth in the most efficient enriched culture, or which were abundant in all samples, or which increased with higher tiamulin concentrations were likely to be the major tiamulin-degrading bacteria. This is the first report suggested the possible roles of Achromobacter, Delftia, Flavobacterium, Pseudomonas, and Stenotrophomonas in tiamulin degradation.