大菱鲆（Scophthalmus maximus）仔稚鱼发育期消化道可培养细菌的菌群特征分析

摘要

Turbot (Scophthatmus maximus) breeding, especially the larval breeding, has been seriously affected by the bacterial diseases that were caused by the interactions of fish, pathogens and the environment. The gastrointestinal flora is the dominant location for the occurrence of diseases. This study is to analyze the gastrointestinal microflora of turbot larvae and expound their formation and succession. Using conventional bacteriological culture techniques, we isolated and quantified the bacteria from the gastrointestinal tract of turbot larvae, tank inlet water and feed in a turbot breeding farm. The dominant strains were identified by sequencing their 16S rDNA for alignment with NCBI 16S rDNA sequences database. The results showed that the total bacteria count in turbot larvae GI tract was increased and then decreased from Day 5 to Day 36. From Day 17 to Day 26, the culturable bacteria in GI tract were approximately 105−106 CFU/g, which showed extremely significant difference compared to the other stages (P<0.01). Similarly, vibrio counts were increased initially and then tended toward stable. Day 17 is the cutoff for the significant differences (P<0.05). Ultimately, the numbers of total bacteria and vibrio remained stable at 104 CFU/g in GI tract. Naturally, Vibrios were the dominant strains in the GI tract of turbot larvae. These results indicated that the dominant bacterial strains in the GI tract changed significantly at different developmental stages of turbot larvae. The bacteria in biological feeding could obviously impact the microflora formation in GI tract in the early stage of turbot, and that Vibrio ichthyoenteri was the dominant strain in the GI tract.%采用传统的细菌培养方法，对大菱鲆(Scophthalmus maximus)育苗生产过程中不同发育时期仔稚鱼的消化道、投喂饵料和养殖水源中的可培养细菌进行了菌群结构分析和优势菌株的16S rDNA 同源性比较，揭示其形成过程和演替规律。结果显示，在大菱鲆仔稚鱼5−36日龄的不同发育时期，消化道中的细菌数量呈现了先升高后降低的变化趋势，在17−26日龄期间，仔稚鱼消化道可培养细菌数量级在105−106 CFU/g 以上，并且与其他时期存在极显著差异(P<0.01)。弧菌总量呈现先升高后稳定的变化趋势，17日龄之前与之后存在显著差异(P<0.05)。至投喂颗粒饵料期，细菌总量和弧菌总量均稳定在104 CFU/g 数量级，弧菌成为大菱鲆仔稚鱼消化道中的优势菌种。本研究发现，大菱鲆仔稚鱼发育早期消化道中的优势菌群变化明显，并且生物饵料中的细菌对消化道中的菌群结构影响较大，其中的 Vibrio ichthyoenteri 最终成为仔稚鱼消化道中的优势菌种。