Effects of phosphorus starvation versus limitation on the marine cyanobacterium Prochlorococcus MED4 I: uptake physiology
Effects of phosphorus starvation versus limitation on the marine cyanobacterium Prochlorococcus MED4 I: uptake physiology
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DOI：
10.1111/1462-2920.12079
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发表时间：
2013-07-01
影响因子：
5.1
通讯作者：
Moore, Lisa R.
中科院分区：
文献类型：
--
作者：
Krumhardt, Kristen M.;Callnan, Kate;Moore, Lisa R.
最近对海洋蓝细菌原绿球藻自然种群的测量表明，在磷有限的海洋区域，这种数量上占优势的光合生物以显着的速率同化磷（P）。为了更好地了解不同磷胁迫条件下原绿球藻的吸收能力，对生长在磷限制恒化器和分批培养中的原绿球藻MED 4进行了吸收动力学实验。我们的研究结果表明，MED 4具有小的细胞特异性V-max，但对P具有高的特异性亲和力（（P）），使其在低P浓度下与其他海洋蓝藻竞争。此外，MED 4调节其吸收动力学响应P胁迫显着增加V-最大值和（P）的无机和有机P（PO 4和ATP）。Michaelis-Menten常数，K-M，为PO 4在不同的P胁迫条件下保持恒定，而K-M为ATP是更高的细胞时，强调PO 4，指出在摄取ATP的额外过程。MED 4从ATP中切割PO 4部分，可能是用5-核苷酸酶样酶而不是碱性磷酸酶。MED 4表现出明显的生理差异下的稳态P限制与那些从P-充满P-饥饿的条件下过渡的细胞。因此，MED 4采用多种策略来应对不断变化的海洋中的P源，并显示出复杂的P胁迫驯化和调节机制。
Recent measurements of natural populations of the marine cyanobacterium Prochlorococcus indicate this numerically dominant phototroph assimilates phosphorus (P) at significant rates in P-limited oceanic regions. To better understand uptake capabilities of Prochlorococcus under different P stress conditions, uptake kinetic experiments were performed on ProchlorococcusMED4 grown in P-limited chemostats and batch cultures. Our results indicate that MED4 has a small cell-specific V-max but a high specific affinity ((P)) for P, making it competitive with other marine cyanobacteria at low P concentrations. Additionally, MED4 regulates its uptake kinetics in response to P stress by significantly increasing V-max and (P) for both inorganic and organic P (PO4 and ATP). The Michaelis-Menten constant, K-M, for PO4 remained constant under different P stress conditions, whereas the K-M for ATP was higher when cells were stressed for PO4, pointing to additional processes involved in uptake of ATP. MED4 cleaves the PO4 moieties from ATP, likely with a 5-nucleotidase-like enzyme rather than alkaline phosphatase. MED4 exhibited distinct physiological differences between cells under steady-state P limitation versus those transitioning from P-replete to P-starved conditions. Thus, MED4 employs a variety of strategies to deal with changing P sources in the oceans and displays complexity in P stress acclimation and regulatory mechanisms.