Hemolytic activity of the mutants M2 and M18 were restored by plasmid complementation. The WT SX strain, the mutant strains M2 and M18, and the complemented strains M2 (pRES-Riean_0790) and M18 (pRES-Riean_0653) were grown in TSB to the mid-logarithmic phase. The bacterial cell pellets were resuspended in phosphate-buffered saline and 10 μL of the cell suspensions were plated on blood agar. The hemolytic zones generated by these strains were observed. Yb2 (dba− strain) was used as a negative control.