16s microbial sequecning of wild Pycnopodia helianthoides experiencnig outbreak of Sea Star Wasting Disease

Sea star wasting (SSW) disease, a massive and ongoing epidemic with unknown cause(s), has led to the rapid death and decimation of sea star populations with cascading ecological consequences. Changes in microbial community structure have been previously associated with SSW, however, it remains unknown if SSW-associated dysbiosis is a mechanism or artifact of disease progression, particularly in wild populations. Here, we compare the microbiomes of the sunflower sea star, Pycnopodia helianthoides, before (Naive) and during (Exposed and Wasting) the initial outbreak in Southeast Alaska to identify changes and interactions in the microbial communities associated with sea star health and disease exposure. We found an increase in microbial diversity (both alpha and beta diversity) preceding signs of disease and an increase in abundance of facultative and obligate anaerobes (most notably Vibrio) in both Exposed (apparently healthy) and Wasting animals. Complementing these changes in microbial composition was the initial gain of metabolic functions upon disease exposure, and loss of function with signs of wasting. Using Bayesian network clustering, we found evidence of dysbiosis in the form of co-colonization of taxa appearing in large numbers among Exposed and Wasting individuals, in addition to the loss of communities associated with Naive sea stars. These changes in community structure suggest a shared set of colonizing microbes that may be important in the initial stages of SSW. Together, these results provide several complementary perspectives in support of an early dysbiotic event preceding visible signs of SSW.

海星消瘦病（Sea star wasting, SSW）是一场规模宏大且持续至今的流行病，其致病原因尚未明确，已导致海星种群快速死亡与大规模消亡，并引发级联式生态后果。既往研究已证实微生物群落结构变化与SSW存在关联，但目前仍未明确：与SSW相关的菌群失调（dysbiosis）究竟是疾病进展的致病机制，还是疾病进程所产生的继发伴随现象，这一点在野生种群中尤为突出。本研究以阿拉斯加东南部地区首次暴发SSW期间的向日葵海星（Pycnopodia helianthoides）为研究对象，对比了健康未暴露组（Naive）、暴露组（Exposed，外观健康）与患病组（Wasting）的微生物组，旨在探究与海星健康及疾病暴露相关的微生物群落变化与互作关系。研究发现，在出现疾病可见症状之前，微生物多样性（涵盖α多样性（alpha diversity）与β多样性（beta diversity））已出现上升；同时，暴露组与患病组个体体内的兼性厌氧菌（facultative anaerobes）与专性厌氧菌（obligate anaerobes）丰度均有所提升，其中弧菌属（Vibrio）的变化最为显著。与微生物组成变化相呼应的是，疾病暴露初期微生物代谢功能出现获得性增强，而当出现消瘦症状时代谢功能则发生丢失。通过贝叶斯网络聚类（Bayesian network clustering）分析，本研究发现了菌群失调的相关证据：暴露组与患病组个体中大量出现的类群发生共定植，同时与健康未暴露组相关的群落出现丢失。这些群落结构变化表明，存在一组共享的定植微生物，它们可能在SSW的初始阶段发挥重要作用。综上，本研究从多个互补视角提供了证据，支持在SSW出现可见症状之前就已发生早期菌群失调事件。