Characterization and in-vivo evaluation of potential probiotics of the bacterial flora within the water column of a healthy shrimp larviculture system

摘要

A thorough understanding of the normal bacterial flora associated with shrimp larviculture systems contributes to probiotic screening and disease control.The bacterial community of the water column over a commercial Litopenaeus vannamei larval rearing mn was characterized with both culture-dependent and culture-independent methods.A total of 27 phylotypes at the species level were isolated and identified based on 16S rDNA sequence analysis.Denaturing gradient gel electrophoresis (DGGE) analysis of the V3-V5 region of 16S rRNA genes showed a dynamic bacterial community with major changes occurred from stages zoea to mysis during the rearing run.The sequences retrieved were affiliated to four phyla,Proteobacteria,Actinobacteria,Bacteroidetes,and Firmicutes,with the family Rhodobacteraceae being the most frequently recovered one.Subsequently,13 representative strains conferred higher larval survival than the control when evaluated in the in-vivo experiments;in particular,three candidates,assigned to Phaeobacter sp.,Arthrobacter sp.,and Microbacterium sp.,significantly improved larval survival (P＜0.05).Therefore,the healthy shrimp larviculture system harbored a diverse and favorable bacterial flora,which contribute to larval development and are of great importance in exploiting novel probiotics.