Four main fractions were exhibited on the TLC plate. The fraction having Rf value 0.70 showed strong antibacterial activity on plate (data not show). The biologically active fraction was isolated for further characterization. HPLC analysis showed that the retention time of the antibacterial compound was 5.9 min, which was the same with that of standard 2,4-diacetylphloroglucinol (2,4-DAPG). HPLC quantification suggested that 2,4-DAPG production of J12 was approximately 40 μg ml−1 (OD600 unit−1).