A Zeaxanthin-Producing Bacterium Isolated from the Algal Phycosphere Protects Coral Endosymbionts from Environmental Stress
A Zeaxanthin-Producing Bacterium Isolated from the Algal Phycosphere Protects Coral Endosymbionts from Environmental Stress
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DOI：
10.1128/mbio.01019-19
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发表时间：
2020-01-01
期刊：
影响因子：
6.4
通讯作者：
Ueda, Mitsuyoshi
中科院分区：
文献类型：
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作者：
Motone, Keisuke;Takagi, Toshiyuki;Ueda, Mitsuyoshi
造礁珊瑚与共生藻科的光合藻类和细菌形成一个复杂的联合体，统称为珊瑚全生生物。这些细菌被假设参与了珊瑚全生物的抗压力，但它们的功能作用在很大程度上仍然难以捉摸。在这里，我们表明，从造礁珊瑚Galaxea fascicularis中分离出的共生藻科藻类与黄杆菌科的新细菌有关。抗生素处理消除了培养的共生菌科细菌，导致PSII的最大量子产率降低（可变荧光除以最大荧光[F-v/F-m]），并增加了生产的活性氧（ROS）在热和光的压力。然后我们分离出这种细菌菌株，命名为GF1。接种GF1后，Fv/Fm值恢复，ROS产生减少。此外，我们发现GF1产生类胡萝卜素玉米黄质，具有强大的抗氧化活性。玉米黄质补充到培养的共生藻科改善Fv/Fm和ROS的生产，表明GF1减轻培养的共生藻科通过玉米黄质生产的热和光胁迫。这些发现可以促进我们对共生菌科细菌和珊瑚全生生物的作用的理解，从而有助于通过使用共生菌及其代谢产物来开发新的珊瑚保护方法。重要性珊瑚礁占海洋面积不到1%，估计拥有所有海洋物种的25%。然而，面对全球气候变化，珊瑚礁的破坏加剧，例如海水温度上升，导致对珊瑚有害的活性氧物质过度产生。虽然造礁珊瑚与细菌和共生藻科的光合内共生藻类形成复杂的联合体，但与珊瑚有关的细菌的功能作用在很大程度上仍然难以捉摸。通过操纵Symbiodiniaceae细菌群落，我们证明了一种产生抗氧化剂类胡萝卜素的细菌可以减轻从造礁珊瑚中分离的培养Symbiodiniaceae的热和光应力。因此，这项研究阐明了珊瑚相关细菌在压力条件下未被探索的作用。
Reef-building corals form a complex consortium with photosynthetic algae in the family Symbiodiniaceae and bacteria, collectively termed the coral holobiont. These bacteria are hypothesized to be involved in the stress resistance of the coral holobiont, but their functional roles remain largely elusive. Here, we show that cultured Symbiodiniaceae algae isolated from the reef-building coral Galaxea fascicularis are associated with novel bacteria affiliated with the family Flavobacteriaceae. Antibiotic treatment eliminated the bacteria from cultured Symbiodiniaceae, resulting in a decreased maximum quantum yield of PSII (variable fluorescence divided by maximum fluorescence [F-v/F-m]) and an increased production of reactive oxygen species (ROS) under thermal and light stresses. We then isolated this bacterial strain, named GF1. GF1 inoculation in the antibiotic-treated Symbiodiniaceae cultures restored the Fv/Fm and reduced the ROS production. Furthermore, we found that GF1 produces the carotenoid zeaxanthin, which possesses potent antioxidant activity. Zeaxanthin supplementation to cultured Symbiodiniaceae ameliorated the Fv/Fm and ROS production, suggesting that GF1 mitigates thermal and light stresses in cultured Symbiodiniaceae via zeaxanthin production. These findings could advance our understanding of the roles of bacteria in Symbiodiniaceae and the coral holobiont, thereby contributing to the development of novel approaches toward coral protection through the use of symbiotic bacteria and their metabolites.IMPORTANCE Occupying less than 1% of the seas, coral reefs are estimated to harbor similar to 25% of all marine species. However, the destruction of coral reefs has intensified in the face of global climate changes, such as rising seawater temperatures, which induce the overproduction of reactive oxygen species harmful to corals. Although reef-building corals form complex consortia with bacteria and photosynthetic endosymbiotic algae of the family Symbiodiniaceae, the functional roles of coral-associated bacteria remain largely elusive. By manipulating the Symbiodiniaceae bacterial community, we demonstrated that a bacterium that produces an antioxidant carotenoid could mitigate thermal and light stresses in cultured Symbiodiniaceae isolated from a reef-building coral. Therefore, this study illuminates the unexplored roles of coral-associated bacteria under stressful conditions.