LAUSR

Abstract Bacillus spp. as probiotics have been widely used in the aquaculture industry. This study was designed to investigate the dietary supplementation of Bacillus cereus QSI-1 with quorum quenching activity, on intestinal barrier and expression levels of innate immune genes. After 14 d of feeding, fish fed with Bacillus cereus QSI-1 exhibited a significant down-regulated gene expression of TNF, IL-8, and IL-10 in the intestinal mucosa, but up-regulated tight junction (TJ) proteins zonula occludens-1 (ZO-1) and occludin and adaptor protein myeloid differentiation factor 88 (MyD88) transcription. This is an indication that Bacillus cereus QSI-1 could enhance intestinal barrier function and activate the non-specific immune system of Crucian carp. At the end of the feeding trial, the Crucian carps in each group were anally infected with A. hydrophila YJ-1. The results showed that Bacillus cereus QSI-1 could prevent the inflammatory response caused by A. hydrophila infection. Histological (integrity of intestinal villi) and qPCR analyses suggested that Bacillus cereus QSI-1 could improve the intestinal barrier function. Taken together, these findings indicate that Bacillus cereus QSI-1 could increase the intestinal epithelial barrier function and innate immune function, and also has the potential to be an alternative agent instead of antibiotics in feed supplements in aquaculture.