Anti-<i>Vibrio</i> activity of <i>Pseudoalteromonas xiamenensis</i> STKMTI.2, a new potential vibriosis biocontrol bacterium in marine aquaculture

We isolated Pseudoalteromonas xiamenensis STKMTI.2 from the mangrove sediments of Setokok Island, Indonesia. This study aimed to identify the bacterium, investigate antagonistic properties and minimum inhibitory concentration, and detect the active compounds using gas chromatography-mass spectrometry. The bacterium was identified using a biochemical test and 16S rDNA sequence analysis. Bioactive compounds were extracted from culture supernatant using EtOAc and examined for antibacterial activities against Vibrio spp. on Zobell 2216E agar medium. The antagonistic test of STKMTI.2 against Vibrio harveyi was conducted for 48 h. Active extracts were purified using preparative layer chromatography and tested for MIC. The anti-Vibrio compound was analysed using GCMS. This bacterium was found to be closest to P. xiamenensis Y2(T), based on the 16S rDNA sequencing analysis. Anti-Vibrio compound was produced after 96 h of incubation. Strain STKMTI.2 inhibited 50% of the pathogenic Vibrio growth in the co-culture test. The substances in the partially purified sample detected by the GCMS analysis included triethoxy-borane; 1,3-diphenyl-1,3,5,5-tetramethyl-cyclotrisiloxane; 1,6-diazaspiro (4.4) nonane-2,7-dione; and 1,3-bis (4-methoxyphenyl)-5-phenyl-1,3,5-triazinane-2-thione. These substances showed much higher activity against Vibrio spp. compared with commercial antibiotics having MIC <= 0.78 mu g ml(-1). This study provides a new report on the anti-Vibrio activity of P. xiamenensis STKMTI.2.