Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China.
Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, China.
PLoS One. 2019 May 8;14(5):e0216590. doi: 10.1371/journal.pone.0216590. eCollection 2019.
Various bacteria that adhere to the gut are important for the health of fish. Regulating the microbial community in a desirable direction may be beneficial in aquaculture for preventing and controlling the diseases caused by pathogenic microbes. In this study, we investigated the changes in the microflora in the intestinal tracts of turbot (Scophthalmus maximus) larvae after introducing a probiotic (Bacillus amyloliquefaciens) after the first feed. B. amyloliquefaciens was added as part of a nutrient enrichment system in live feed (Branchionus plicatilis or Artemia sinica), so it passed into the intestinal tracts of the newly hatched turbot larvae. The turbot larvae were fed on live feed containing B. amyloliquefaciens in the experimental group, whereas live feed without the probiotic was provided to larvae in the control group. The total bacterial genomic DNA in the larval guts was extracted and sequenced with an Illumina HiSeq PE250 system. According to the sequencing results, the abundances of microbial species and the microflora diversity were lower in the intestines in the experimental group than the control. Throughout development, the microflora structure in the intestines was mainly constructed before the first feed and the composition of the dominant operational taxonomic units (OTUs) was stable, where the abundances of OTU8, OTU124, OTU150, OTU107, and OTU17 were always high. Compared with the control, the structures of the microflora in the intestines were similar on different days during the development and the growth of larvae in the experimental group. However, the similarity of the microflora structure between different treatments was low on the same day. Furthermore, the mean proportion of common OTUs was only 74.7% in different treatments on each day, which indicates that the introduction of B. amyloliquefaciens in the live feed changed the microflora structure in the intestine. During the early development stage (days 3-30), the average abundance of Pseudomonas was reduced by 0.8% whereas that of Lactococcus increased by 3.5% in the experimental group. Pseudomonas spp. are considered potentially pathogenic bacteria but there is no direct evidence for the pathogenicity of Lactococcus in turbot. Moreover, several Lactococcus species are regarded as probiotics in aquaculture. Therefore, the use of B. amyloliquefaciens could be beneficial for optimizing the microbial community structure in the intestines of turbot larvae, which may explain the probiotic effect of B. amyloliquefaciens. This study provides a theoretical basis for the biological regulation of the microflora structure in the intestinal tract during turbot breeding.
各种附着在肠道上的细菌对鱼类的健康很重要。在水产养殖中，调节微生物群落朝着理想的方向发展可能有助于预防和控制由病原微生物引起的疾病。在这项研究中，我们在第一次投喂后，研究了益生菌（解淀粉芽孢杆菌）引入牙鲆（Scophthalmus maximus）幼虫肠道后肠道微生物群的变化。解淀粉芽孢杆菌作为活饵（褶皱臂尾轮虫或卤虫）营养强化系统的一部分添加，因此它进入了刚孵化的牙鲆幼虫的肠道。实验组的牙鲆幼虫以含有解淀粉芽孢杆菌的活饵为食，而对照组的幼虫则以不含益生菌的活饵为食。采用 Illumina HiSeq PE250 系统提取幼虫肠道内的总细菌基因组 DNA 并进行测序。根据测序结果，实验组幼虫肠道内的微生物种类丰度和微生物多样性均低于对照组。在整个发育过程中，肠道微生物群结构主要在第一次投喂前构建，优势操作分类单元（OTU）的组成稳定，其中 OTU8、OTU124、OTU150、OTU107 和 OTU17 的丰度始终较高。与对照组相比，实验组幼虫在不同日龄的肠道微生物群结构在发育和生长过程中相似。然而，在同一日龄，不同处理之间的微生物群结构相似性较低。此外，不同处理之间共有 OTU 的平均比例仅为 74.7%，这表明活饵中添加解淀粉芽孢杆菌改变了肠道内的微生物群结构。在早期发育阶段（第 3-30 天），实验组中假单胞菌的平均丰度降低了 0.8%，而乳球菌的丰度增加了 3.5%。假单胞菌被认为是潜在的病原菌，但没有直接证据表明乳球菌对牙鲆具有致病性。此外，一些乳球菌被认为是水产养殖中的益生菌。因此，使用解淀粉芽孢杆菌可能有利于优化牙鲆幼虫肠道内的微生物群落结构，这可以解释解淀粉芽孢杆菌的益生菌作用。本研究为牙鲆养殖过程中肠道微生物群结构的生物调控提供了理论依据。
