THE EFFECT OF Bacillus sp. N-acyl-Homoserine-Lactone (AHL) DEGRADING BACTERIA ISOLATED FROM MICROALGAE CULTURE Skeletonema sp. TO THE QUORUM SENSING SYSTEM OF Vibrio sp. AND SURVIVAL OF WHITE SHRIMP POST LARVAE (Litopennaeus vannamei) CHALLENGED WITH Vibrio sp.

• Main Author: NURFATHURAHMI - (21116032), ADANI
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20706
• Institution: Institut Teknologi Bandung

Vibriosis in shrimp aquaculture is one of the major disease problems that affect the productivity and sustainability of the aquaculture industry. This disease caused by infection of pathogenic bacteria Vibrio sp. Antibiotics and chemical subtances has thus far been used to cure or prevent bacterial infection, but an inappropriate dossage and long term use of this substances are able to develope bacterial resistance. Therefore, it is necessary to find an alternative method to handle this. Virulence of Vibrio sp. has been regulated by quorum sensing system, which is regulated by secretion and sensing signal molecule called autoinducer. Biodegradation of this signal molecule by bacteria could be an alternative method to depressed virulence of Vibrio sp. In the previous study, AHL-degrading bacteria was isolated from microalgal culture Skeletonema sp. This study was aimed to determine the effect of addition Bacillus sp. to the quorum sensing system of Vibrio sp. and the survival rate of white shrimp larvae (Litopennaeus vannamei) when challenged by Vibrio sp. This research divided into three consecutive stages: (1) N-hexanoyl-homoserine-lactone (HHL) as AHL analog compound microbial degradation assay using HPLC method. (2) Impact of addition Bacillus sp. on quorum sensing-regulated bioluminescence of Vibrio sp., detected by tecan multireader, and (3) white shrimp post-larvae challenge test against Vibrio sp. with six different treatment during ten day culture period. The result showed that Bacillus sp. isolated from Skeletonema sp. has the ability to degrade HHL with degradation rate 0.28 mg.l-1.h-1. This bacteria also able to inactivate AHL molecules produced by Vibrio sp, that shown by decreasing of biolumincescense significantly during 12 hours incubation periods. Addition of Bacillus sp. to the white shrimp culture significantly improved survival of the post-larvae at three different delivery time (p<0.05) when challenged with Vibrio sp. The addition of Bacillus sp. and Vibrio sp. in the same period gave the highest survival of white shrimp post-larvae of 64.1%, followed by Bacillus addition 24 hours before addition of Vibrio sp. (survival: 62.6%) and Bacillus sp. addition 24 hours after addition of Vibrio sp. (survival: 56.2%). All of those treatments was significantly different compared to only addition of Vibrio sp. (survival: 22.7%). It could be concluded that Bacillus sp. is able to disrupt quorum sensing system of Vibrio sp. and significantly increase the survival of white shrimp post-larvae. Thus, this isolates have the potential to be used in aquaculture as a probiotic agent in order to prevent vibriosis.