Disease in the marine environment is predicted to increase with anthropogenic stressors and already affects major habitat-formers, such as corals and seaweeds. Solutions to address this issue are urgently needed. The seaweed Delisea pulchra is prone to a bleaching disease, which is caused by opportunistic pathogens and involves bacterial dysbiosis. Bacteria that can inhibit these pathogens and/or counteract dysbiosis are therefore hypothesised to reduce disease. This study aimed to identify such disease-protective bacteria and investigate their protective action. One strain, Phaeobacter sp. BS52, isolated from healthy D. pulchra, was antagonistic towards bleaching pathogens and significantly increased the proportion of healthy individuals when applied before the pathogen challenge (pathogen-only vs. BS52 + pathogen: 41–80%), and to a level similar to the control. However, no significant negative correlations between the relative abundances of pathogens and BS52 on D. pulchra were detected. Instead, inoculation of BS52 mitigated pathogen-induced changes in the epibacterial community. These observations suggest that the protective activity of BS52 was due to its ability to prevent dysbiosis, rather than direct pathogen inhibition. This study demonstrates the feasibility of manipulating bacterial communities in seaweeds to reduce disease and that mitigation of dysbiosis can have positive health outcomes.

预计海洋环境中的疾病会随着人为压力源的增加而增加，并且已经影响到主要的栖息地形成者，例如珊瑚和海藻。迫切需要解决这个问题的解决方案。海藻Delisea pulchra容易出现白化病，这是由机会性病原体引起的，涉及细菌生态失调。因此，假设可以抑制这些病原体和/或抵消生态失调的细菌可以减少疾病。本研究旨在鉴定这种疾病保护细菌并研究它们的保护作用。一种菌株，Phaeobacter sp。BS52，从健康的D. pulchra中分离，对漂白病原体具有拮抗作用，并在病原体攻击前应用时显着增加健康个体的比例（仅病原体与 BS52 + 病原体：41-80%），并达到与对照相似的水平。然而，没有检测到病原体的相对丰度与D. pulchra上的 BS52 之间存在显着的负相关。相反，接种 BS52 减轻了病原体引起的表观细菌群落变化。这些观察结果表明，BS52 的保护活性是由于它能够防止生态失调，而不是直接抑制病原体。这项研究证明了操纵海藻中的细菌群落以减少疾病的可行性，并且减轻生态失调可以产生积极的健康结果。