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Add To Calendar 28/04/2016 09:10:0028/04/2016 09:30:00Africa/JohannesburgAsian-Pacific Aquaculture 2016AHL-degrading bacterium reduce the virulence of Vibrio campbellii toward giant freshwater prawn Macrobrachium rosenbergii larvae Crystal 4The World Aquaculture Societyjohnc@was.orgfalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY

AHL-degrading bacterium reduce the virulence of Vibrio campbellii toward giant freshwater prawn Macrobrachium rosenbergii larvae

Pande Gde Sasmita J.1*, Peter Bossier2, Tom Defoirdt2
1Dept of Aquatic Resources Management, Udayana University, Bali, Indonesia 80361.
2Lab of Aquaculture and ARC, Ghent University, Rozier 44, 9000 Ghent, Belgium.

Aquaculture is the fastest-growing food-producing sector worldwide. One of the major aquaculture species is the giant freshwater prawn, Macrobrachium rosenbergii. However, diseases caused by various opportunistic pathogenic bacteria constitute a significant obstacle for the further expansion of M. rosenbergii cultivation. Frequent use of antibiotics has resulted in the development and spread of antibiotic resistance. Recently, biodegradation of quorum sensing (QS) molecules has been proposed as a method of anti-infective strategy to combat bacterial diseases in aquaculture. One of the most important aquaculture pathogens, Vibrio campbellii, contains a three-channel quorum sensing system with three different types of signal molecules (HAI-1, AI-2 and CAI-1, respectively) feeding a shared signal transduction cascade. HAI-1 is an AHL (N-acylated-L-homoserine lactone), the most common autoinducer used by Gram-negative bacteria. It has been reported that the HAI-1 and the AI-2 mediated channels of the V. campbellii quorum sensing system are essential for full virulence to M. rosenbergii larvae.

The AHL-degrader Bacillus sp. NFMI-C was isolated from microalgae Chaetoceros muelleri culture. In this study, we tested their influence on the growth (as expressed by the larval stage index -LSI) and survival of prawn larvae challenged with V. campbellii. An N-hexanoyl-L-homoserine lactone (HHL) degradation assay showed that the isolate was able to degrade HHL. Because bioluminescence is one of the phenotypes that are regulated by quorum sensing in V. campbellii, we used bioluminescence as a read-out of quorum sensing activity and determined the impact of the isolate on bioluminescence of wild type V. campbellii. We found that Bacillus sp. NFMI-C can inhibit QS-regulated luminescence of V. campbellii (Figure 1). Finally, addition of Bacillus sp. NFMI-C to the rearing water resulted in a significantly improved survival of larvae of the giant river prawn M. rosenbergii when challenged with V. campbellii without any effect on larval growth (Table 1). These results showed that the AHL-degrading bacterium isolated from microalgae could be useful as novel disease control strain for aquaculture.

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