Metabolic Rhythms of the Cyanobacterium Cyanothece sp ATCC 51142 Correlate with Modeled Dynamics of Circadian Clock
Metabolic Rhythms of the Cyanobacterium Cyanothece sp ATCC 51142 Correlate with Modeled Dynamics of Circadian Clock
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DOI：
10.1177/0748730409338367
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发表时间：
2009-08-01
影响因子：
3.5
通讯作者：
Nedbal, Ladislav
中科院分区：
文献类型：
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作者：
Cerveny, Jan;Nedbal, Ladislav
这些实验旨在揭示单细胞、固氮蓝藻蓝藻在代谢过程中的动态特征。当暴露于不同的昼夜节律强迫模式(LD 16：8、LD 12：12、LD 8：16、LD 6：6)时。叶绿素浓度从主观光照开始的早晨到中午前后迅速增长，然后在下午晚些时候和整个夜间保持稳定。在735 nm处测得的光密度在上午叶绿素积累期间是稳定的，然后在下午早些时候增加并趋于峰值，然后在黄昏时迅速下降到深夜的稳定状态。作者认为，这些动力学在很大程度上反映了糖原颗粒的积累和随后的消耗。这一假说与呼吸作用的尖锐峰值一致，与假定的碳氢化合物分解代谢相一致。在长日照法(LD 16：8)中，这些事件可能标志着在黄昏发生的有氧光合代谢向微氧氮代谢的转变，因此不能被随后的黑暗所触发。相反，控制很可能起源于发出黑夜来临信号的生物钟。为了探索呼吸和昼夜节律振荡之间的联系的动力学，作者推断了从细长聚球藻到蓝藻的KaiABC振荡器的早期模型。黄昏时测得的呼吸活动峰值在时间和时间宽度上与Kaib 4复合体积累的模型峰值密切相关，这标志着生物钟的下午晚些时候。作者提出了一种假设，高水平的Kaib4(或其蓝藻sp.类似物)触发实验中反映在呼吸高峰的糖原分解代谢。在半昼夜节律(LD6：6)期间，进一步检验了模拟的Kaib4动力学与实验测得的呼吸活动峰值的动力学之间的相关程度。该模型预测了KaiABC振荡器的不规则模式，这与机械或电子时钟起搏器非常不同，后者在以两倍于其内源频率的频率驱动时会受到强烈的抑制。这一极不寻常的动态模式在实验上得到了证实，有力地支持了昼夜节律模型的正确性和所提出的与呼吸直接相关的结论。
These experiments aim to reveal the dynamic features that occur during the metabolism of the unicellular, nitrogen fixing cyanobacterium Cyanothece sp. when exposed to diverse circadian forcing patterns (LD 16: 8, LD 12: 12, LD 8: 16, LD 6: 6). The chlorophyll concentration grew rapidly from subjective morning when first illuminated to around noon, then remained stable from later in the afternoon and throughout the night. The optical density measured at 735 nm was stable during the morning chlorophyll accumulation, then increased in the early afternoon toward a peak, followed at dusk by a rapid decline toward the late night steady state. The authors propose that these dynamics largely reflect accumulation and subsequent consumption of glycogen granules. This hypothesis is consistent with the sharp peak of respiration that coincides with the putative hydrocarbon catabolism. In the long-day regimen (LD 16: 8), these events may mark the transition from the aerobic photosynthetic metabolism to microaerobic nitrogen metabolism that occurs at dusk, and thus cannot be triggered by the darkness that comes later. Rather, control is likely to originate in the circadian clock signaling an approaching night. To explore the dynamics of the link between respiration and circadian oscillations, the authors extrapolated an earlier model of the KaiABC oscillator from Synechococcus elongatus to Cyanothece sp. The measured peak of respiratory activity at dusk correlated strongly in its timing and time width with the modeled peak in accumulation of the KaiB 4 complex, which marks the late afternoon phase of the circadian clock. The authors propose a hypothesis that high levels of KaiB 4 (or of its Cyanothece sp. analog) trigger the glycogen catabolism that is reflected in the experiments in the respiratory peak. The degree of the correlation between the modeled KaiB 4 dynamics and the dynamics of experimentally measured peaks of respiratory activity was further tested during the half-circadian regimen (LD 6: 6). The model predicted an irregular pattern of the KaiABC oscillator, quite unlike mechanical or electrical clock pacemakers that are strongly damped when driven at double their endogenous frequency. This highly unusual dynamic pattern was confirmed experimentally, supporting strongly the validity of the circadian model and of the proposed direct link to respiration.