Evolution of Antibiotic Resistance Genes and Bacterial Community During Erythromycin Fermentation Residue Composting Under High‐Salinity Stress

The removal efficiency of antibiotic resistance genes (ARGs) is the biggest challenge for the treatment of erythromycin fermentation residue (EFR). In the current research, spray-dried EFR was composted with bulking materials, consisting of cattle manure and maize straw, at ratios of 0% (control), 10% (T1), and 30% (T2) for 30 days. Environmental factors and bacterial community on the behaviors of ARGs were further investigated. Apart from the high levels of erythromycin, the electrical conductivities were also increased by 66.7% and 291.7% in the samples of T1 and T2, respectively. After 30 days of composting, total ARGs in the samples of control were decreased by 78.1%-91.2%, but those of T1 and T2 were increased 14.5–16.7- and 38.5–68.7-fold. ARGs related to ribosomal protection ( erm ) dominated the samples of T1 and T2 at day 13 and 30, especially that ermF accounted for more than 80% of the total ARGs. Furthermore, the results of bacterial community revealed that EFR promoted the growth of Proteobacteria and Bacteroidetes , but inhibited that of Actinobacteria , Verrucomicrobia and Chloroflexi . Network analysis revealed that the enriched ARGs had strong correlation with seven bacterial genera, including Halomonas , Oceanobacillus , and Alcaligenes , most of which are halotolerant. Therefore, erythromycin combined with high salinity can have synergistic effect on the enrichment of ARGs and their hosts