3.1 Hemolytic activity of surfactin
Surfactin has strong hemolytic activity [20]. We detected the hemolytic activity of surfactin using the agar plates containing sheep blood cells, and found WH1 showed obvious hemolytic activity around the colony, but the mutant strain ΔsrfA without surfactin production lost this ability. We further determined the hemolytic activity in broth, and found it was also disappeared in ΔsrfA (Fig. S1 in supplementary materials). Thereby, the hemolytic activity could be used for representation of the surfactin production in different strains.