Isolation and characterization of new potential probiotic bacteria based on quorum-sensing system

Abstract

Aims: 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. Methods and 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 1011 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. Significance and Impact of the Study: 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.

Exploiting Quorum Sensing To Confuse Bacterial Pathogens

“…Bacterially mediated quorum quenching using AiiA was also demonstrated to be beneficial against plant pathogens, both when aiiA was expressed in the pathogenic bacterium itself and during coinoculation of the pathogen with bacteria naturally producing AiiA or engineered bacterial strains expressing heterologous AiiA (88,89,(93)(94)(95)(96). AiiA was also shown to have potential for use in aquaculture, as carp fed either recombinant AiiA protein or Bacillus expressing aiiA were more resistant to infection by the fish pathogen Aeromonas hyrophila (361,362). Separately, AHLdegrading enrichment cultures (EC) of undefined microbial isolates naturally associated with marine organisms have been evaluated for use as probiotic cultures in aquaculture.…”

Antibiotics in Aquaculture – Use, Abuse and Alternatives

“…Bacteria that are able to degrade quorum sensing molecules might be useful as biocontrol agents in aquaculture. To date, several bacteria of aquatic origin have been studied for their quorum quenching properties (Chu et al, 2011;Defoirdt et al, 2004;Defoirdt et al, 2008;Merrifield et al, 2010;Nakayama et al, 2009;Nhan et al, 2010;Tinh et al, 2007;Tinh et al, 2008). Marine Bacillus and Halobacillus salinus have been shown to quench the quorum sensing system of Vibrio harveyi (Musthafa et al, 2011;Teasdale et al, 2009).…”

“…Marine Bacillus and Halobacillus salinus have been shown to quench the quorum sensing system of Vibrio harveyi (Musthafa et al, 2011;Teasdale et al, 2009). A Bacillus (QSI)-1-like bacteria isolated from the intestine of the fish Carassius auratus gibelio can degrade AHLs in vitro and reduced the amount of AHLs and the extracellular protease activity of Aeromonas hydrophila in coculture with the fish pathogen (Chu et al, 2011). Carp fed a diet supplemented with (QSI)-1 showed good survival after an experimental infection with Aeromonas hydrophila compared with those fed a control diet (Chu et al, 2011).…”

N-hexanoyl-L-homoserine lactone-degrading Pseudomonas aeruginosa PsDAHP1 protects zebrafish against Vibrio parahaemolyticus infection

“…The bacteria were incubated in TSB at 30 C for 24 h, centrifuged at 5000Âg for 10 min, and the harvested cells serially diluted in sterile saline to 6 or 10 7 CFU ml À1 of GFP-VpDAHV2. After the immersion, the fish were released into the fibreglass reinforced plastics tank and mortality was recorded for 10 days [21]. Virulence of GFP-VpDAHV2 was determined based on LD 50 which was calculated using the Probit method [22].…”

“…They were (1) Group A (P. aeruginosa control), being fed with PsDAHP1-containing feed and no challenge; (2) Group B (positive control), being fed with basal feed and challenged with GFP-VpDAHV2; (3) Group C (experimental group); being fed with PsDAHP1-containing feed and challenged with GFPVpDAHV2; and (4) Group D (negative control), being fed with basal feed and no challenge. Fish mortality was recorded daily for 30-days [21], following the challenge; dead and moribund fish were removed and moribund fish examined for the presence of GFPVpDAHV2 in the gills and intestine.…”