RP-HPLC analysis and antibacterial activity test of fractions. (A) RP-HPLC (HPLC type: Agilent 1100) analysis of M-1 GSC culture supernatant using a Luna C18 column (100 Å 150 × 4.6 mm, Phenomenex, Aschaffenburg, Germany). (B) Antibacterial activity test of HPLC fractions of M-1 GSC culture supernatant. 15 paper discs loaded with HPLC fractions were put onto LB agar mixed with the two Erwinia strains. The numbers below paper discs indicate different fractions. Fractions 3 corresponding to the peak at retention time 2 min in the M-1 culture supernatant HPLC chromatogram showed antagonistic effects against the growth of E. amylovora Ea273 (left) and E. carotovora (right). “ + ” represents positive control, discs loaded with M-1 culture supernatant, while “-” represents negative control, discs loaded with sterile water. (C) HPLC-ESI-MS analysis of fraction 3.