The Vibrio-predatory filamentous bacteria effectively removed acute hepatopancreatic necrosis disease (AHPND) causative Vibrio parahaemolyticus in vitro

Acute hepatopancreatic necrosis (AHPND) caused by pathogenic Vibrio parahaemolyticus strains (VpAHPND) and other Vibrio spp. resulted in significant economic losses (over USD 7 billion) in shrimp aquaculture. Several biocontrol strategies for VpAHPND have been proposed, including the use of probiotics, immunization and bioflocs. However, each of these alternatives has limitations, with varying success in removing VpAHPND from aquatic environments. The potential of Vibrio-predatory filamentous bacteria (VPFB) as a biocontrol agent on VpAHPND was investigated in this work. Three VPFBs from the genera Saprospira (CCB-QB6) and Aureispira (CCB-E and F) were isolated from seagrass habitat in Penang, Malaysia. The VPFBs inhibited the multiplication of VpAHPND as well as other Vibrio species such as V. owensii, V. harveyi, and V. alginolyticus. The VpAHPND and VPFB co-culture experiments showed that within 15 h of introducing strain E or F, the VpAHPND cell number was reduced to less than 1 x 104 cells/ml from an initial (1 x 107 cells/ml). Scanning electron microscopy revealed that VPFBs formed cell aggregates with VpAHPND within a few minutes by attachment on the cell surface of VPFBs cells before the Vibrio cells destroyed. These findings indicate that VPFBs have the potential to be used as a biocontrol agent for VpAHPND in shrimp aquaculture.