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 were decreased after treatment with heat, but the inhibitory activities of strain P . SW-1 CFS were still effective after treatment with proteinase Kfor 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.