NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton
NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton
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DOI：
10.1038/s41396-018-0285-8
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发表时间：
2019-03-01
期刊：
影响因子：
11
通讯作者：
Cassar, Nicolas
中科院分区：
文献类型：
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作者：
Berthelot, Hugo;Duhamel, Solange;Cassar, Nicolas
氮（N）是世界海洋广大区域的限制性营养素，但对各种浮游植物群体可用的N的来源仍然知之甚少。在这项研究中，我们调查了无机碳（C）固定率和硝酸盐（NO3-），铵（NH 4+）和尿素吸收率在单细胞水平的光合微微真核生物（PPE）和蓝藻原绿球藻和聚球藻。为此，我们使用了双重N-15和C-13标记的孵育试验，结合流式细胞术细胞分选和nanoSIMS分析，对在北太平洋副热带环流（NPSG）和加州海流系统（CCS）中收集的样本进行分析。基于这些分析，我们发现，PPE的光合作用的增长率（基于C固定）是较高的CCS比NSPG，而观察到相反的原绿球藻。还原形式的N（NH 4+和尿素）占大多数的N收购的所有研究组。NO3-在所有组中代表了总氮吸收的减少部分，但PPE（平均17.4 +/- 11.2%）高于原绿球藻和聚球藻（平均分别为4.5 +/- 6.5和2.9 +/- 2.1%）。这可能部分解释了这些微微型浮游生物群体的对比地理学。此外，单细胞分析表明，细胞间的异质性微微浮游生物组内的NO3-吸收显着大于C固定和NH 4+吸收。我们假设，细胞异质性的NO3-摄取组内促进适应NO3-在环境中的波动可用性。
Nitrogen (N) is a limiting nutrient in vast regions of the world's oceans, yet the sources of N available to various phytoplankton groups remain poorly understood. In this study, we investigated inorganic carbon (C) fixation rates and nitrate (NO3-), ammonium (NH4+) and urea uptake rates at the single cell level in photosynthetic pico-eukaryotes (PPE) and the cyanobacteria Prochlorococcus and Synechococcus. To that end, we used dual N-15 and C-13-labeled incubation assays coupled to flow cytometry cell sorting and nanoSIMS analysis on samples collected in the North Pacific Subtropical Gyre (NPSG) and in the California Current System (CCS). Based on these analyses, we found that photosynthetic growth rates (based on C fixation) of PPE were higher in the CCS than in the NSPG, while the opposite was observed for Prochlorococcus. Reduced forms of N (NH4+ and urea) accounted for the majority of N acquisition for all the groups studied. NO3- represented a reduced fraction of total N uptake in all groups but was higher in PPE (17.4 +/- 11.2% on average) than in Prochlorococcus and Synechococcus (4.5 +/- 6.5 and 2.9 +/- 2.1% on average, respectively). This may in part explain the contrasting biogeography of these picoplankton groups. Moreover, single cell analyses reveal that cell-to-cell heterogeneity within picoplankton groups was significantly greater for NO3- uptake than for C fixation and NH4+ uptake. We hypothesize that cellular heterogeneity in NO3- uptake within groups facilitates adaptation to the fluctuating availability of NO3- in the environment.