Holobiont phenotype results from a combination of host and symbiont genotypes as well as from prevailing environmental conditions that alter the relationships among symbiotic members. Corals exemplify this concept, where shifts in the algal symbiont community can lead to some corals becoming more or less thermally tolerant. Despite linkage between coral bleaching and disease, the roles of symbiotic bacteria in holobiont resistance and susceptibility to disease remains less well understood. This study thus characterizes the microbiome of disease‐resistant and ‐susceptible Acropora cervicornis coral genotypes (hereafter referred to simply as ‘genotypes’) before and after high temperature‐mediated bleaching. We found that the intracellular bacterial parasite ‘Ca. Aquarickettsia rohweri’ was strikingly abundant in disease‐susceptible genotypes. Disease‐resistant genotypes, however, had notably more diverse and even communities, with correspondingly low abundances of ‘Ca. Aquarickettsia’. Bleaching caused a dramatic reduction of ‘Ca. Aquarickettsia’ within disease‐susceptible corals and led to an increase in bacterial community dispersion, as well as the proliferation of opportunists. Our data support the hypothesis that ‘Ca. Aquarickettsia’ species increase coral disease risk through two mechanisms: (i) the creation of host nutritional deficiencies leading to a compromised host‐symbiont state and (ii) the opening of niche space for potential pathogens during thermal stress.

中文翻译：

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寄生“罗氏梭菌”（Candidatus Aquarickettsia rohweri）是鹿角菌（Acropora cervicornis）中疾病易感性的标志，但在热应激中会丢失

Holobiont表型的产生是宿主和共生基因型的组合，以及改变共生成员之间关系的主要环境条件。珊瑚就是这种概念的体现，藻类共生体群落的变化会导致某些珊瑚变得或多或少具有耐热性。尽管珊瑚白化与疾病之间存在联系，但共生细菌在全盐菌抗性和疾病易感性中的作用仍知之甚少。因此，本研究表征了高温介导的漂白前后抗病和易感的鹿角珊瑚珊瑚基因型（以下简称为“基因型”）的微生物组。我们发现细胞内细菌寄生虫'钙。在疾病易感基因型中，罗氏无水藻非常丰富。然而，抗病基因型的多样性甚至社区更为明显，Ca '的丰度相对较低。Aquarickettsia' 。漂白导致Ca的急剧降低。易感染疾病的珊瑚中发生了水产立克次体病，并导致细菌群落扩散的增加​​以及机会主义者的扩散。我们的数据支持“ Ca。水产立克次体的物种通过两种机制增加了珊瑚病的风险：（i）导致寄主共生状态受损的寄主营养不足，以及（ii）在热应激期间为潜在病原体打开了利基空间。