Diel rhythmicity in amino acid uptake by Prochlorococcus
Diel rhythmicity in amino acid uptake by Prochlorococcus
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DOI：
10.1111/j.1462-2920.2008.01633.x
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发表时间：
2008-08-01
影响因子：
5.1
通讯作者：
Zubkov, Mikhail V.
中科院分区：
文献类型：
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作者：
Mary, Isabelle;Garczarek, Laurence;Zubkov, Mikhail V.
海洋蓝细菌原绿球藻是地球上最丰富的光养生物，在氮（N）耗尽的海洋环流中占浮游植物的主导地位。除了无机氮源，如亚硝酸盐和铵，该属的自然种群也获得有机氮，特别是氨基酸。在这里，我们调查使用同位素示踪剂和流式细胞仪细胞分选技术是否由原绿球藻的氨基酸摄取受到昼夜节律，如果是这样，这是否与一个特定的细胞周期阶段。我们观察到，在对比聚球藻细胞的蛋氨酸吸收率，明显的昼夜节律在热带大西洋原绿球藻细胞的蛋氨酸吸收。这些节奏得到证实，使用可重复的cyclostat实验与光同步的纯原绿球藻（PCC 9511株）的文化和S-35-蛋氨酸和H-3-亮氨酸示踪剂。细胞在黎明时以较低的速率获得示踪剂，而在黄昏时以较高的速率获得示踪剂，尽管培养基中的铵浓度高出> 10（4）倍，这可能是因为氨基酸可以直接掺入蛋白质中。S+G（2）细胞周期阶段的细胞摄取亮氨酸的速率始终比G（1）阶段的细胞高2.2倍。此外，S+G（2）细胞从黎明到黄昏上调氨基酸摄取3.5倍，以促进细胞分裂前的蛋白质合成。由于原绿球藻种群可以占总微生物摄取蛋氨酸的13%在中午到42%在黄昏，可能是其他氨基酸的N-贫化海洋沃茨，这属施加昼夜变化，其他浮游细菌种群的强大竞争压力。
The marine cyanobacterium Prochlorococcus, the most abundant phototrophic organism on Earth, numerically dominates the phytoplankton in nitrogen (N)-depleted oceanic gyres. Alongside inorganic N sources such as nitrite and ammonium, natural populations of this genus also acquire organic N, specifically amino acids. Here, we investigated using isotopic tracer and flow cytometric cell sorting techniques whether amino acid uptake by Prochlorococcus is subject to a diel rhythmicity, and if so, whether this was linked to a specific cell cycle stage. We observed, in contrast to diurnally similar methionine uptake rates by Synechococcus cells, obvious diurnal rhythms in methionine uptake by Prochlorococcus cells in the tropical Atlantic. These rhythms were confirmed using reproducible cyclostat experiments with a light-synchronized axenic Prochlorococcus (PCC9511 strain) culture and S-35-methionine and H-3-leucine tracers. Cells acquired the tracers at lower rates around dawn and higher rates around dusk despite > 10(4) times higher concentration of ammonium in the medium, presumably because amino acids can be directly incorporated into protein. Leucine uptake rates by cells in the S+G(2) cell cycle stage were consistently 2.2 times higher than those of cells at the G(1) stage. Furthermore, S+G(2) cells upregulated amino acid uptake 3.5 times from dawn to dusk to boost protein synthesis prior to cell division. Because Prochlorococcus populations can account from 13% at midday to 42% at dusk of total microbial uptake of methionine and probably of other amino acids in N-depleted oceanic waters, this genus exerts diurnally variable, strong competitive pressure on other bacterioplankton populations.