Microbial communities associated with the nursery stage of commercially cultivated seaweed Saccharina japonica in Southern China

Epimicrobiota associated with seaweeds are crucial for the health and development of their hosts due to their ability to produce phytohormones and vitamins etc. However, there is limited knowledge related to the microbiota of commercially cultivated seaweed Saccharina japonica . In this study, we investigated the dynamics of microbiota associated with S. japonica at nursery stage using Illumina sequencing of the V3-V4 hypervariable region of 16S rRNA gene. The composition and structure of epimicrobiota showed significant differences at the transition time (from mature sporophytes to sporelings). While, the epimicrobiota were relatively stable during the development of sporelings. Blastopirellula and Pseudoalteromonas were the dominant genera of the community of mature sporophytes and 6-week-old sporelings, respectively. Rubritalea was the most dominant genus for both 7 and 8-week-old sporelings. These three genera were also part of the core microbiota, suggesting that they may play an essential function within the S. japonica holobiont. In addition, members of the Planctomicrobium and Roseibacillus were identified as both drivers and keystone species, which might be responsible for the epimicrobiota shifts from 7-week-old sporelings to 8-week-old sporelings and were fundamental for the newly assembled epimicrobiota. Our results enrich the baseline data related to the microbiota of the commercially cultivated S. japonica .