Identification of highly-adhesive gut Lactobacillus strains in zebrafish (Danio rerio) by partial rpoB gene sequence analysis
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abstract
The objective of the present study was to identify the highly-adhesive gut Lactobacillus strains in zebrafish (Danio rerio) by employing partial rpoB gene and denaturing gradient gel electrophoresis (DGGE). A four-week feeding trial (twice a day to visual satiation) with two diets, a control diet and a probiotic diet supplemented with ten probiotic Lactobacillus strains at equal amounts (6.0107 cells/g control diet), was conducted in a recirculation aquaculture system (20 fish/tank, 6 tanks/treatment). Adhesive gut bacteria were sampled 1h later after the second feeding at the experimental start and the end of 1, 2, 3, and 4weeks, respectively. The results showed that the composition of predominant adhesive gut lactobacilli varied greatly in strain richness and relative abundance during the feeding period. Lactobacillus brevis CGMCC 1.2028, Lactobacillus buchneri BU 222, Lactobacillus plantarum subsp. plantarum JCM 1149T, Lactobacillus rhamnosus CICC 6141, and L. rhamnosus JCM 20300 were identified as the highly-adhesive gut strains of the second week samples based on both DGGE and clone library analysis. The protective effects of highly- and less-adhesive strains JCM 1149T and Lactobacillus acidophilus JCM 1132T (106-8 cells/g diet) on zebrafish were compared in an immersion challenge with Aeromonas hydrophila NJ-1 after 14-day-feeding. Strain JCM 1149T performed obviously more efficiently than strain JCM 1132T against strain NJ-1 in vitro. This strengthened the judgment that gastrointestinal (GI) tract adhesion is a favorable property of dietary probiotics as biocontrol agents in aquaculture. It was concluded that DGGE analysis based on partial rpoB gene-PCR was efficient to screen and qualitatively monitor the highly-adhesive gut strains from potential probiotic lactobacilli as zebrafish a model fish species. 2012 Elsevier B.V.
