Intracellular competition for nitrogen controls dinoflagellate population density in corals
Intracellular competition for nitrogen controls dinoflagellate population density in corals
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DOI：
10.1098/rspb.2020.0049
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发表时间：
2020-03-11
影响因子：
4.7
通讯作者：
Meibom, Anders
中科院分区：
文献类型：
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作者：
Krueger, Thomas;Horwitz, Noa;Meibom, Anders
共生珊瑚组织中甲藻微藻的密度是珊瑚动物健康和生产力的重要决定因素。然而，由于过去解决密度波动的精细代谢后果的方法学限制，其调节的具体机制和珊瑚营养的后果尚未得到充分了解。在这里，我们描述了共生体密度变化对红海 Stylophora pistillata 菌落和组织水平的生理和营养影响。共生体光生理学的改变在广泛的共生体密度范围内维持了珊瑚的生产力和宿主营养。然而，我们证明，单个共生细胞之间的密度依赖性营养竞争，表现为氮同化和细胞生物量的减少，可能为共生体种群增长创造了负反馈机制，最终定义了稳态密度。尽管共生体氮同化发生了根本性变化，但我们没有发现与密度相关的代谢最佳值，超过该最佳值宿主营养物同化或组织生物量就会下降，这表明在环境条件下通常观察到的共生体密度范围内，宿主营养需求得到了充分满足。
The density of dinoflagellate microalgae in the tissue of symbiotic corals is an important determinant for health and productivity of the coral animal. Yet, the specific mechanism for their regulation and the consequence for coral nutrition are insufficiently understood due to past methodological limitations to resolve the fine-scale metabolic consequences of fluctuating densities. Here, we characterized the physiological and nutritional consequences of symbiont density variations on the colony and tissue level in Stylophora pistillata from the Red Sea. Alterations in symbiont photophysiology maintained coral productivity and host nutrition across a broad range of symbiont densities. However, we demonstrate that density-dependent nutrient competition between individual symbiont cells, manifested as reduced nitrogen assimilation and cell biomass, probably creates the negative feedback mechanism for symbiont population growth that ultimately defines the steady-state density. Despite fundamental changes in symbiont nitrogen assimilation, we found no density-related metabolic optimum beyond which host nutrient assimilation or tissue biomass declined, indicating that host nutrient demand is sufficiently met across the typically observed range of symbiont densities under ambient conditions.