Isolation and characterization of new potential probiotic bacteria based on quorum-sensing system.
OBJECTIVE
This work was aimed at identifying strains which can degrade quorum-sensing (QS) molecules from fish gut, with properties suitable for use as probiotic in aquaculture.


RESULTS
A total of 200 strains were obtained from the intestine gut of Carassius auratus gibelio after enrichment in KG medium contained 500 μg l(-1) of C6-HSL as the sole source of carbon and nitrogen; one strain named QS inhibitor (QSI)-1 was identified as the genus Bacillus spp. by morphological phenotypes, and the strain also possessed an aiiA homologue gene using PCR amplification. In vitro, QSI-1 strongly interfered with violacein production by Chromobacterium violaceum. Coculture of QSI-1 with fish pathogen effectively reduced the amount of acyl-homoserine lactones (AHLs) and the extracellular proteases activity of Aeromonas hydrophila YJ-1. The oral LD50 of QSI-1 to fish was more than 10(11) CFU shown that it was avirulent to fish. Fish fed diet supplemented with QSI-1 had good survival, suggesting that QSI-1 showed protection against Aer. hydrophila infection.


CONCLUSIONS
The results indicate that the isolate QSI-1 might have the potential possibility to be used as a probiotic in aquaculture.


CONCLUSIONS
This is the first report to describe a bacterium isolated from the intestine gut of C. auratus gibelio which can degrade AHLs and has the probiotic characteristics for its use in aquaculture.
Department of Microbiology, School of Life Science & Technology, China Pharmaceutical University, Nanjing, China. chuweihua2002@yahoo.com.cn
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D054742:Acyl-Butyrolactones / Q000378:metabolism; D016980:Aeromonas hydrophila / Q000201:enzymology / Q000378:metabolism; D000818:Animals; D017756:Aquaculture; D001419:Bacteria / Q000302:isolation & purification; D005393:Fish Diseases / Q000517:prevention & control*; D005798:Genes, Bacterial; D006054:Goldfish / Q000382:microbiology; D016905:Gram-Negative Bacterial Infections / Q000517:prevention & control; D007422:Intestines / Q000382:microbiology; D010447:Peptide Hydrolases / Q000096:biosynthesis; D019936:Probiotics / Q000627:therapeutic use*; D053038:Quorum Sensing
D054742:Acyl-Butyrolactones; D010447:Peptide Hydrolases