Symbiodiniaceae are a diverse family of marine dinoflagellates, well known as coral endosymbionts. Isolation and in vitro culture of Symbiodiniaceae strains for physiological studies is a widely adopted tool, especially in the context of understanding how environmental stress perturbs Symbiodiniaceae cell functioning. While the bacterial microbiomes of corals often correlate with coral health, the bacterial communities co-cultured with Symbiodiniaceae isolates have been largely overlooked, despite the potential of bacteria to significantly influence the emergent physiological properties of Symbiodiniaceae cultures. We examined the physiological response to heat stress by Symbiodiniaceae isolates (spanning three genera) with well-described thermal tolerances, and combined these observations with matched changes in bacterial composition and abundance through 16S rRNA metabarcoding. Under thermal stress, there were Symbiodiniaceae strain-specific changes in maximum quantum yield of photosystem II (proxy for health) and growth rates that were accompanied by changes in the relative abundance of multiple Symbiodiniaceae-specific bacteria. However, there were no Symbiodiniaceae-independent signatures of bacterial community reorganisation under heat stress. Notably, the thermally tolerant Durusdinium trenchii (ITS2 major profile D1a) had the most stable bacterial community under heat stress. Ultimately, this study highlights the complexity of Symbiodiniaceae-bacteria interactions and provides a first step towards uncoupling their relative contributions towards Symbiodiniaceae physiological functioning.

中文翻译：

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在热胁迫下揭示共生菌科微生物组的变化。

共生菌科是海洋鞭毛藻的一个多样化家族，众所周知为珊瑚内共生体。用于生物学研究的共生菌科菌株的分离和体外培养是一种广泛采用的工具，尤其是在了解环境压力如何扰动共生菌科细胞功能的背景下。尽管珊瑚的细菌微生物群通常与珊瑚健康相关，但与细菌共生菌分离培养物共培养的细菌群落却被大大地忽视了，尽管细菌具有显着影响共生菌科细菌新出现的生理特性的潜力。我们检查了具有良好热耐受性的共生菌科菌株（跨越三个属）对热胁迫的生理反应，并将这些观察结果与通过16S rRNA元条形码进行的细菌组成和丰度的匹配变化相结合。在热胁迫下，光合系统II（为健康的代理人）的最大量子产量和生长速率伴随着共生双菌科菌株的特定变化，并伴随着多个共生双菌科特定细菌的相对丰度的变化。但是，在热胁迫下，没有细菌群落重组的共生二齿科独立特征。值得注意的是，在热胁迫下，耐热的硬皮硬壳小麦（ITS2主要特征D1a）具有最稳定的细菌群落。最终，这项研究突出了共生菌科细菌相互作用的复杂性，并为分离它们对共生菌科生理功能的相对贡献提供了第一步。