Changes of microbial community structures associated with seedlings of Saccharina japonica at early stage of outbreak of green rotten disease

The giant farming industry of the kelp Saccharina japonica in China relies on supply of seedlings. In the seedling hatchery, green rotten disease is one of the dreadful diseases which may lead to a complete failure of hatchery operation when it breaks out. The changes of the bacterial community associated with seedlings at early stage of green rotten disease are largely unknown. To address this question, we have analyzed the structures of bacterial community using 16S rRNA gene sequencing and made comparisons of the structure in the healthy tissues with that of diseased ones. The data showed that microbial diversity increased and the bacterial community composition changed at early stage of green rotten disease. The genera of Granulosicoccus, Litorimonas, Tenacibaculum, and Blastopirellula were dominance on the diseased tissues and increased dramatically compared with the healthy ones. This indicated that these four genera were probably associated with green rotten disease of seedlings in S. japonica. This detailed comparison of bacterial communities between healthy and diseased tissues on juvenile kelp extends current knowledge on microbial community assembly on diseased seedlings of kelp.