WGS of Escherichia coli
The donor strain (FN), which exhibited the highest conjugation frequency, was selected for wholegenome sequencing. Briefly, the strain was cultured overnight in LB broth at 37 with shaking. Bacterial cells were harvested by centrifugation and washed twice with sterile PBS. Total genomic DNA was extracted and submitted to Sangon Biotech (Shanghai) Co., Ltd. for wholegenome sequencing. Sequencing was performed on the Illumina NovaSeq 6000 platform using a pairedend 150 bp strategy. Raw sequencing reads were subjected to quality control using Trimmomatic (version 0.36)  to remove adapter sequences and low-quality bases. The cleaned reads were assembled using SPAdes (version 3.5.0) . Gene annotation of the assembled genome was performed using the RAST database  and the Bakta database . The mcr-1 harboring plasmid was designated as pFN-8. Its replicon type, genetic structure, multidrug resistance region, and distribution characteristics of mobile genetic elements were analyzed via BLAST alignment against the NCBI nucleotide database.