Disease outbreaks cause severe economic losses in commercially cultivated Saccharina japonica. Epiphytic bacteria are increasingly recognized to play an important role in S. japonica health and may also become opportunistic pathogens when the environment deteriorates. However, there is little knowledge about the epiphytic bacterial communities associated with commercially cultivated S. japonica and how these communities change over the harvest season. We analyzed the diversity, composition, and temporal dynamics of epiphytic bacterial communities associated with both healthy and diseased tissue of S. japonica over a harvest season (from April to June, 2015) at Ailian Bay, Rongcheng, China. Our results showed that Proteobacteria and Bacteroidetes were the main phyla and Halomonas spp. were the most dominant bacterial species. Halomonadaceae, Hyphomonadaceae, Rhodobacteraceae, and Phyllobacteriaceae families were abundant in both healthy and diseased S. japonica, but the relative abundance of these bacteria differed between healthy and diseased groups. Spatial (site 1, site 2, and site 3 in April) and temporal comparisons (site 3 from April to June) revealed that the bacterial community associated with cultivated S. japonica was influenced by sampling time and sampling site independent of the health status. Several OTUs from the Roseobacter group, including members of the genera Sulfitobacter and Loktanella, were enriched in diseased tissues suggesting these taxa could be candidate opportunistic pathogens. In contrast, OTUs belonging to the genera Halomonas were enriched in healthy tissues, indicating a potential beneficial role for group during the cultivation of S. japonica. Our results provide important baseline knowledge of the epiphytic bacterial communities and possibly pathogenic bacteria associated with commercially cultivated S. japonica.

疾病暴发导致商业化种植的日本粳稻造成严重的经济损失。人们逐渐认识到附生细菌在粳稻健康中起着重要作用，并且当环境恶化时也可能成为机会性病原体。但是，关于与商业栽培的日本粳稻相关的附生细菌群落以及这些群落在收获季节如何变化的知识很少。我们分析的多样性，构成，并与健康和患病组织相关附生细菌群落的时间动态国槐荣城爱莲湾的一个收获季节（2015年4月至6月）。我们的研究结果表明，变形杆菌和拟杆菌是主要的门志和嗜盐单胞菌。是最主要的细菌种类。Halomonadaceae，Hyphomonadaceae，Rhodobacteraceae和Phyllobacteriaceae家庭都在健康丰富和患病国槐，但这些细菌的相对丰度健康和患病群体之间的差异。空间（4月的站点1，站点2和站点3）和时间比较（4月至6月的站点3）显示，细菌群落与栽培的日本粳稻有关。不受采样时间和采样位置的影响，不受健康状况的影响。迷迭香属的几个OTU，包括硫杆菌属和Loktanella属的成员，在患病组织中富集，表明这些类群可能是机会病原体。相反，属于Halomonas属的OTU在健康组织中富集，表明该组在日本血吸虫的培养过程中具有潜在的有益作用。我们的结果提供了与商业栽培的日本粳稻有关的附生细菌群落和可能的病原菌的重要基础知识。