Destabilisation of the holobiont macroalga and induction of bacterial pathogenesis due to increasing environmental stress conditions

海洋大型藻类（海藻）的表面由复杂的细菌群落定殖。最近已经证明，这些表观细菌群落的组成是特定于宿主的。这种关联的干扰或变化可能危及整个实体的健康。在过去的十年里，海带Ecklonia radiata的死亡率很高。病原性感染以及环境压力条件的增加，例如由于气候变化导致的海水温度升高，可能导致澳大利亚以及更普遍地在地球的温带地区形成海带物种的主要栖息地的巨大损失。 了解海藻holobiont和它是如何受到全球变暖趋势的影响，深入了解细菌holobiont成员和促成这种特定的宿主-微生物协会的因素是迫切需要的。本研究的目的是探讨全生体E.辐射的季节和区域尺度上沿着增加的水温梯度开始在澳大利亚南部的北方分布限制这条河。结合温度控制的围隔实验，本次调查将确定的因素，有助于稳定的藻类holobiont和阐明这个系统可以不稳定的环境压力条件。该提案的总体目标是验证以下假设：环境胁迫条件升高直接影响藻类代谢物的表面渗出，这将破坏宿主微生物及其相关细菌之间的自然平衡。这反过来将为病原体提供空间，导致感染或将在自然伴侣中诱导发病。

Surfaces of marine macroalgae (seaweeds) are colonised by complex bacterial communities. It has recently been demonstrated that the composition of these epibacterial communities are specific to the host alga. Disturbances or shifts in this association can compromise the health of the whole entity. The kelp seaweed Ecklonia radiata has undergone high rates of mortality in the last decade. Pathogenic infections as well as increased environmental stress conditions, such as elevated seawater temperature due to climate change, are possibly causative for the tremendous loss of the dominant habitat forming kelp species in Australia, and more generally in temperate regions of the planet. Understanding the seaweed holobiont and how it is affected by global warming trends, in-depth knowledge of the bacterial holobiont members and the factors contributing to this specific host-microbe association is urgently required. This proposal aims to investigate the composition and stability of the holobiont E. radiata on a seasonal and regional scale along an increasing water temperature gradient beginning in the south of Australia towards the northern distributional limit of this alga. In combination with a temperature manipulated mesocosm experiment, this investigation will identify the factors contributing to the stability of the algal holobiont and elucidate how this system can be destabilized by environmental stress conditions. The overall goal of this proposal is to verify the hypothesis that elevated environmental stress conditions directly affect the surface exudation of algal metabolites which will destabilise the natural balance between host alga and its associated bacteria. This in turn will provide space for pathogens resulting in infection or will induce pathogenesis in natural associates.