Characteristics of inhibitory active substances produced by Pseudoalteromonas SW-1

To confirm the antagonistic activity characterization of the strain Pseudoalteromonas SW-1 (P. SW-1), its cell-free supernatant (CFS) was studied against a clam pathogenic strain of Vibrio Alginolyticu MP-1 (V.MP-1). The CFS of P. SW-1 exhibited evident antagonistic activities against the pathogens, and the absorbance value (600 nm) of V. MP-1 remained at a lower level at 24 h when compared with the control. The results showed that the inhibitory activities of strain P. SW-1 CFS showed differences after treatment with heat, acid and alkali, and proteinase K. The CFS of P. SW-1 inhibitory activities decreased after treatment with heat, but the inhibitory activities of strain P. SW-1 CFS were still effective after treatment with proteinase K for 24 h. The acid and alkali treatments could increase the inhibitory activities of strain P. SW-1 CFS. Therefore, the ammonium sulfate precipitation test also indicated that P. SW-1 could produce some active protein compounds to antagonize pathogenic V. MP-1.