Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium.
Combined effects of different CO2 levels and N sources on the diazotrophic cyanobacterium Trichodesmium.
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DOI：
10.1111/ppl.12172
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发表时间：
2014-10
影响因子：
6.4
通讯作者：
Rost B
中科院分区：
文献类型：
--
作者：
Eichner M;Kranz SA;Rost B
为了预测气候变化的影响和可能的反馈，关键是要了解背后的机制CO2响应的生态地球化学相关的浮游植物物种。先前对丰富的N2固定剂Trichodesmium的实验显示出强烈的CO2响应，这归因于其碳（C）和氮（N）获取之间的能量重新分配。为了实现这一假设，我们通过在不同的CO2分压（pCO2）水平（180，380，980和1400 µatm）和N源（N2和NO3−）下生长Trichodesmium crystraeum IMS 101来操纵细胞能量预算。随后，生物量的生产和主要的能量产生过程（光合作用和呼吸）和能量消耗过程（N2固定和C获取）进行了测量。而氧通量和叶绿素荧光表明能量产生和其日周期既不受pCO2也不受N源的影响，细胞的生产率和组成不同。pCO2升高增加N2固定和有机C和N含量。固氮酶活性的刺激程度高于细胞内容物，表明pCO2对从N2到生物量的转移效率的影响。pCO2依赖的变化，在N2固定的昼夜周期与C亲和力，确认N和C收购之间的相互作用。关于氮源的影响，在NO3−生长的细胞中，生产率提高，我们将其归因于与N2固定相比更高的N保留和更低的ATP需求。pCO2对C亲和力的影响在NO3−使用者中不如N2固定者明显。我们的研究说明了理解不同环境条件下的能量收支和通量的必要性，以解释pCO2上升的间接影响。
To predict effects of climate change and possible feedbacks, it is crucial to understand the mechanisms behind CO2 responses of biogeochemically relevant phytoplankton species. Previous experiments on the abundant N2 fixers Trichodesmium demonstrated strong CO2 responses, which were attributed to an energy reallocation between its carbon (C) and nitrogen (N) acquisition. Pursuing this hypothesis, we manipulated the cellular energy budget by growing Trichodesmium erythraeum IMS101 under different CO2 partial pressure (pCO2) levels (180, 380, 980 and 1400 µatm) and N sources (N2 and NO3−). Subsequently, biomass production and the main energy-generating processes (photosynthesis and respiration) and energy-consuming processes (N2 fixation and C acquisition) were measured. While oxygen fluxes and chlorophyll fluorescence indicated that energy generation and its diurnal cycle was neither affected by pCO2 nor N source, cells differed in production rates and composition. Elevated pCO2 increased N2 fixation and organic C and N contents. The degree of stimulation was higher for nitrogenase activity than for cell contents, indicating a pCO2 effect on the transfer efficiency from N2 to biomass. pCO2-dependent changes in the diurnal cycle of N2 fixation correlated well with C affinities, confirming the interactions between N and C acquisition. Regarding effects of the N source, production rates were enhanced in NO3− grown cells, which we attribute to the higher N retention and lower ATP demand compared with N2 fixation. pCO2 effects on C affinity were less pronounced in NO3− users than N2 fixers. Our study illustrates the necessity to understand energy budgets and fluxes under different environmental conditions for explaining indirect effects of rising pCO2.
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