Boilard Aurélie, Dubé Caroline E, Gruet Cécile, Mercière Alexandre, Hernandez-Agreda Alejandra, Derome Nicolas
Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec City, QC G1V 0A6, Canada.
California Academy of Sciences, 55 Music Concourse Drive, San Francisco, CA 94118, USA.
Microorganisms. 2020 Oct 29;8(11):1682. doi: 10.3390/microorganisms8111682.
Coral microbiomes are critical to holobiont health and functioning, but the stability of host-microbial interactions is fragile, easily shifting from eubiosis to dysbiosis. The heat-induced breakdown of the symbiosis between the host and its dinoflagellate algae (that is, "bleaching"), is one of the most devastating outcomes for reef ecosystems. Yet, bleaching tolerance has been observed in some coral species. This review provides an overview of the holobiont's diversity, explores coral thermal tolerance in relation to their associated microorganisms, discusses the hypothesis of adaptive dysbiosis as a mechanism of environmental adaptation, mentions potential solutions to mitigate bleaching, and suggests new research avenues. More specifically, we define coral bleaching as the succession of three holobiont stages, where the microbiota can (i) maintain essential functions for holobiont homeostasis during stress and/or (ii) act as a buffer to mitigate bleaching by favoring the recruitment of thermally tolerant Symbiodiniaceae species (adaptive dysbiosis), and where (iii) environmental stressors exceed the buffering capacity of both microbial and dinoflagellate partners leading to coral death.
珊瑚微生物群对共生体的健康和功能至关重要，但宿主与微生物之间相互作用的稳定性很脆弱，很容易从共生状态转变为失调状态。热诱导宿主与其甲藻共生关系的破坏（即“白化”），是珊瑚礁生态系统最具毁灭性的后果之一。然而，在一些珊瑚物种中观察到了白化耐受性。本综述概述了共生体的多样性，探讨了珊瑚与其相关微生物有关的耐热性，讨论了适应性失调作为一种环境适应机制的假说，提及了减轻白化的潜在解决方案，并提出了新的研究途径。更具体地说，我们将珊瑚白化定义为共生体的三个阶段的连续过程，在此过程中，微生物群可以（i）在应激期间维持共生体稳态的基本功能，和/或（ii）通过促进耐热共生藻物种的招募来充当减轻白化的缓冲剂（适应性失调），以及（iii）环境压力源超过微生物和甲藻伙伴的缓冲能力导致珊瑚死亡。
