SCREENING AND IDENTIFICATION OF BACILLUS TO INHIBIT QUORUM SENSING

Bacterial diseases are one of the main reasons to damage the health of aquaculture. It is a new research direction to prevent and control aquatic animal diseases by inhibiting the Quorum sensing (QS) that could regulate the pathogen virulence. The purpose of the present experiment was to screen the Bacillus strain to inhibit the QS, the Chromobacterium violaceum was used as the reporting strain to analyze the Bacillus strain F3-1, F3-2, F6-4, F6-5, X77, X93 and X3914 that the isolations from carassius auratus gibelio intestine tract or preserved in the lab by using T type streak cultivation and filter-paper-diffusion. The results of T type streak cultivation showed that strain F3-1 could inhibit the production of violacein of Chromobacterium violaceum; the results of filter-paper-diffusion indicated that the materials to inhibit the production of violacein of Chromobacterium violaceum was in the extracellular products of strain F3-1.Then, the crude extracts was taken from the culture of strain F3-1, and the OD585 of violacein of Chromobacterium violaceum was determined at the concentration of crude extracts of 0, 50, 100, 200 and 300 mg/L, and the results indicated that the production of violacien significantly decreased with the increasing of crude extracts concentration (P0.05); No violacien was observed in the test tube when the concentration of crude extracts reached 200mg/L. The protein of crude extracts was taken by the method of ammonium sulfate precipitation. The results showed that the extracellular proteins were probably the material to inhibit the QS of Chromobacterium violaceum. The strain F3-1 was identified as Bacillus pumilus (GenBank accession No. JX984444) by 16S rDNA sequence analysis. So, Bacillus pumiluswas isolated from carassius auratus gibelio intestine tract could inhibit the bacterial Quorum sensing.