人工培育对虾苗种体内可培养细菌数量及组成分析

The Analysis of the Quantity and the Composition of Cultivable Bacteria in Artificiallly Cultivated Prawn Larvae

采用常规细菌分离、培养与纯化，结合细菌16S rDNA序列分析等方法，调查分析了山东、天津、浙江部分苗种场凡纳滨对虾（Litopenaeus vannamei）和中国明对虾（Fenneorpenaeus chinensis）苗种体内的可培养细菌总数以及优势菌的种类和数量，并用PCR的方法检测对虾苗种携带病毒情况。结果显示，凡纳滨对虾和中国明对虾苗种体内的可培养细菌总数均在10^5–10^7 CFU/g之间，分离出的细菌分属于弧菌属（Vibrio）、发光杆菌属（Photobacterium）、芽孢杆菌属（Bacillus）、盐单胞菌属（Halomonas）等8个属，其中，弧菌属在对虾苗种体内占绝对优势，达40.0%–90.23%。部分凡纳滨对虾和中国明对虾苗种样品检测为白斑综合征病毒（White spot syndrome virus, WSSV）和传染性皮下及造血组织坏死病毒（Infectious hypodermal and hematopoietic necrosis virus, IHHNV）阳性，WSSV检出率为50.0%，IHHNV检出率为37.5%，同时携带两种病毒的检出率为11.11%。只携带WSSV病毒以及同时携带两种病毒的对虾苗种体内的总菌数量在1.23×10^7–4.14×10^7 CFU/g之间，显著高于其他批次的样品（P＜0.05），且弧菌数量在10^7 CFU/g左右，显著高于其他批次的样品（P＜0.05）。只携带IHHNV以及不携带病毒的对虾苗种体内的弧菌数量为10^4–10^6 CFU/g。研究表明，弧菌属在凡纳滨对虾和中国明对虾苗种体内普遍存在且为优势菌属，携带WSSV可能会引起对虾苗种体内的弧菌数量增长。

Healthy postlarvae is the prominent factor in the shrimp aquaculture. Bacterial and viral diseases have been seriously harmful in the shrimp industry, therefore it is important to study the qualitative and quantitative characteristics of the bacteria and virus in the shrimp. In this study we collected the bacterial flora in the post-larvae of Litopenaeus vannamei and Fenneorpenaeus chinensis in the breeding fields in Shandong, Tianjin and Zhejiang. The isolated strains were purified and identified by using conventional methods as well as the 16S rDNA sequence analysis method. We also detected the white spot syndrome virus （WSSV） and the infectious hypodermal and haematopoietic necrosis virus （IHHNV） using the PCR method. According to our results, the total amount of the cultured bacteria in the post larvae was 10^5–10^7 CFU/g. The isolated bacteria belong to the genus of Vibrio, Photobacterium, Bacillus, Halomonas, Biaionia, Marinobacter, Polaribacter, and Planococcus. Vibrio accounted for the largest proportion in the dominant bacteria, which was from 40.00% to 90.23%. The uneven distribution of bacteria implied that there were more individual species but less categorical species of bacteria. There were WSSV and IHHNV positive samples in both L. vannamei and F. chinensis. The WSSV positive rate was 50.0% and the IHHNV positive rate was 37.5%, and 11.11% of the samples were infected with both. The post-larvae infected with either WSSV or both carried a total amount of bacteria from 1.23×10^7 CFU/g to 4.14×10^7 CFU/g, and the amount of Vibrio was about 10^7 CFU/g, both of which was significantly higher than other samples （P〈0.05）. The amount of Vibrio in the uninfected postlarvae or those infected with IHHNV only was between 10^4 to 10^6 CFU/g. Our studies demonstrated that Vibrio ubiquitously existed in the post-larvae of L. vannamei and F. chinensis, and that infection with WSSV might increase the amount of Vibrio in the larvae. Future investigation is needed to identify the associated risk in the shrimp culture.