Bacillus sp. QSI-1 Modulate Quorum Sensing Signals Reduce Aeromonas hydrophila Level and Alter Gut Microbial Community Structure in Fish

Abstract

Quorum sensing (QS) is a cell density dependent process that enables bacteria to communicate with each other based on the production, secretion and sensing of the auto-inducer molecules and then subsequently regulate virulence associated gene expression. Interrupting quorum sensing may represent a novel alternative approach to combat bacterial pathogen. Several bacteria can produce quorum quenching (QQ) enzymes. However, the role of QQ bacteria in shaping the microbiota and the level of N-acyl-homoserine lactones (AHLs, a prevalent type of QS molecules) producing bacteria remains largely unknown. The objective of this study was to examine the presence of AHLs in the fish intestine and investigate the modulation of gut microbiota and its effect on Aeromonas hydrophila level by a QQ enzyme producing probiotic Bacillus sp. QSI-1. AHLs were found in fish gut content and were confirmed in Aeromonas species using Chromobacterium violaceum CV026 and Agrobacterium tumefaciens AT 136 (pZLR4) as reporter strains. We demonstrated that the composition of fish gut microbiota was affected by quenching bacteria QSI-1, and the percentage of A. hydrophila was decreased significantly. Taken together, these results provide valuable insights into QQ enzyme producing probiotics can modulate the microbiota structure and decrease the percentage of AHL-producing pathogenic bacteria in the gut. These data strongly suggest that QQ probiotics may serve as non-antibiotic feed additive in aquaculture to control bacterial diseases.

iQSP: A Sequence-Based Tool for the Prediction and Analysis of Quorum Sensing Peptides Using Informative Physicochemical Properties

“…. , 2 8 ) of the SVM model. The identification of informative PCPs using GA-SAR algorithm is described as follows:…”

“…In addition, a wide-ranging variety of other signaling molecules have also been identified [7], including fatty acids used by Xanthomonas spp., Burkholderia spp., Xylella spp. [8], ketones (Vibrio spp. and Legionella spp.…”

Quorum Quenching Properties and Probiotic Potentials of Intestinal Associated Bacteria in Asian Sea Bass Lates calcarifer

“…The involvement of the intestinal microflora in promoting health and modulating the immunity of fish is well documented, and modulation of the gut ecosystem using probiotics is increasingly adopted [22,44]. Selection of appropriate probionts requires in vitro preliminary tests, which assay the bacteria for the safety to host, sensitivity to antibiotics, tolerance to low pH and bile salts, their growth in and adherence to mucus, antagonistic properties against pathogens, production of relevant digestive exoenzymes, derivation from the host and favorable growth characteristics [45].…”

“…Application of AHL degrading bacteria able to utilize AHL molecules of marine and freshwater pathogens as a food source is a developing idea due to their previously successful outcomes [17][18][19][20][21][22]. However, the majority of the strains that have been tested in the past are allochthonous QQ bacteria [21,23].…”

Indigenous AHL‐degrading bacteriumBacillus firmussw40 affects virulence of pathogenicAeromonas hydrophilaand disease resistance of gibel carp

“…In this study, B. firmus sw40 supplemented in feed significantly reduced the inflammatory cytokines TNF‐1a, TNF‐2a and IFN‐γ genes expression (Figure ), antioxidant parameter MDA and GSH levels, and increased antioxidant enzyme SOD activity in gibel carp (Table ). The gastrointestinal tract is a main infection route of A. hydrophila in freshwater fishes (Chu & Lu, ; Zhang et al, ; Zhou, Zhang, Yin, & Chu, ) and inhabited by a high diverse microorganism community (Gajardo et al, ; Kashinskaya et al, ; Wu et al, ). Bacillus firmus sw40 colonizing in the intestine of fish host could degrade the AHLs secreted by pathogenic bacteria and lower the fish inflammation induced by the virulence factors.…”