The supply of healthy sporelings plays a crucial role in the successful aquaculture of commercially cultivated brown kelp Saccharina japonica. Epibacteria are of critical importance for maintaining seaweed health and development. Thus, this study aimed to investigate the epibacterial community associated with mature sporophytes and 1.5- and 2.0-month-old sporelings, as well as juvenile sporophytes of S. japonica by using 16S rRNA gene amplicon sequencing and predicted the bacterial functional profiles. We found that Proteobacteria, Verrucomicrobia, Bacteroidetes, and Planctomycetes were the main phyla, while Loktanella and Rubritalea and Persicirhabdus were the dominant genera for all four developmental stages. Highly abundant core microbiota included Persicirhabdus, Loktanella, Litorimonas, and Rubritalea. Further analysis of the predicted functions showed that different metabolic functions were involved at different developmental stages. More metabolic functions were found in 2-month-old sporelings and mature sporophytes. Both the diversity, composition of the epiphytic bacterial communities, and metabolic functions changed according to different developmental stages at least in 1.5- and 2-month-old sporelings. Our results not only provide fundamental knowledge for the epibacteria associated with S. japonica but will also help nursery farms in preventing and mitigating the disease outbreaks by monitoring the variations of the epibacterial communities at the nursery stage.

健康的孢子的供应在商业化养殖褐海带糖粳稻的成功水产养殖中起着至关重要的作用。表细菌对维持海藻的健康和发育至关重要。因此，本研究旨在探讨与成熟的孢子体和1.5和2.0个月大的孢苗，以及少年孢子体相关的epibacterial社区国槐用16S rRNA基因扩增子测序和预测细菌的功能配置文件。我们发现Proteobacteria，Verrucomicrobia，Bacteroidetes和Planctomycetes是主要的门，而Loktanella和Rubritalea和Persicirhabdus是所有四个发育阶段的主要属。高度丰富的核心微生物群包括Persicirhabdus，Loktanella，Litorimonas和Rubritalea。对预测功能的进一步分析表明，不同的代谢功能参与了不同的发育阶段。在两个月大的孢子和成熟的孢子体中发现了更多的代谢功能。至少在1.5个月和2个月大的孢子中，附生细菌群落的多样性，组成和代谢功能均根据不同的发育阶段而变化。我们的结果不仅提供了与日本血吸虫有关的表生细菌的基础知识。 但是通过在苗圃阶段监测表观细菌群落的变化，也将帮助苗圃农场预防和减轻疾病暴发。