The increase in prevalence and severity of coral disease outbreaks produced by Vibrio pathogens, and related to global warming, has seriously impacted reef-building corals throughout the oceans. The coral Oculina patagonica has been used as a model system to study coral bleaching produced by Vibrio infection. Previous data demonstrated that when two coral pathogens (Vibrio coralliilyticus and Vibrio mediterranei) simultaneously infected the coral O. patagonica, their pathogenicity was greater than when each bacterium was infected separately. Here, to understand the mechanisms underlying this synergistic effect, transcriptomic analyses of monocultures and cocultures as well as experimental infection experiments were performed. Our results revealed that the interaction between the two vibrios under culture conditions overexpressed virulence factor genes (e.g., those encoding siderophores, the type VI secretion system, and toxins, among others). Moreover, under these conditions, vibrios were also more likely to form biofilms or become motile through induction of lateral flagella. All these changes that occur as a physiological response to the presence of a competing species could favor the colonization of the host when they are present in a mixed population. Additionally, during coral experimental infections, we showed that exposure of corals to molecules released during V. coralliilyticus and V. mediterranei coculture induced changes in the coral microbiome that favored damage to coral tissue and increased the production of lyso-platelet activating factor. Therefore, we propose that competition sensing, defined as the physiological response to detection of harm or to the presence of a competing Vibrio species, enhances the ability of Vibrio coral pathogens to invade their host and cause tissue necrosis.

中文翻译：

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毒力是珊瑚弧菌病原体种间相互作用的副作用。


由弧菌病原体引起的、与全球变暖有关的珊瑚疾病爆发的流行率和严重程度的增加，严重影响了整个海洋的造礁珊瑚。 Oculina patagonica珊瑚已被用作研究弧菌感染引起的珊瑚白化的模型系统。先前的数据表明，当两种珊瑚病原体（珊瑚弧菌和地中海弧菌）同时感染珊瑚O. patagonica时，其致病性比每种细菌单独感染时的致病性更大。在这里，为了了解这种协同效应的机制，对单一培养物和共培养物进行了转录组分析以及实验性感染实验。我们的结果表明，两种弧菌在培养条件下的相互作用导致毒力因子基因过度表达（例如，编码铁载体、VI 型分泌系统和毒素等的基因）。此外，在这些条件下，弧菌也更有可能形成生物膜或通过诱导侧鞭毛变得活动。当宿主存在于混合种群中时，作为对竞争物种的存在的生理反应而发生的所有这些变化可能有利于宿主的定植。此外，在珊瑚实验感染过程中，我们发现，珊瑚暴露于解珊瑚弧菌和地中海弧菌共培养期间释放的分子，会引起珊瑚微生物组的变化，有利于珊瑚组织的损伤，并增加溶血血小板激活因子的产生。 因此，我们提出，竞争感知（定义为对检测伤害或竞争性弧菌物种存在的生理反应）增强了弧菌珊瑚病原体侵入宿主并导致组织坏死的能力。