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Mechanisms of oxygen evolution in cyanobacteria and its acquisition process(es)

蓝细菌的析氧机制及其获取过程

基本信息

批准号：
15370021
负责人：
MIMURO Mamoru
金额：
$ 7.3万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

In order to understand the molecular mechanism of oxygen evolution in cyanobacteria and its acquisition process(es) during the evolution from anoxygenic photosynthetic bacteria to cyanobacteria, we selected one unique species of cyanobacteria, i.e., Gloeobacter violaceus PCC 7421 that lacks thylakoid membranes, a representative example of its primitive characteristics.1.First of all, we determined the complete genome sequence of G.violcaeus by the co-operative research with the Kazusa DNA Research Institute (DNA Res. 10,137,2003). The genome information revealed that this species lacks many genes relating to photosynthesis and other metabolic pathways ; for example, kai A/B/C for circadian rhythm.2.We tried to construct the transformation system of this species, however at the moment, we have not yet succeeded the development of the system. A rigid cell wall may be the cause for incorporation of exogenous gene.3.We directly evaluated the oxygen evolution properties of this species. The steady-state oxygen evolution activity was approximately 250 μmoleO2/mg Chl/hr, a little lower than that estimated on Synechocystis sp.PCC 6803. A typical feature was a very high activity in respiration, approximately 10 times higher than that in Synechocystis sp.PCC 6803. This clearly indicates difference in the electron transfer system in G.violaceus where respiratory and photosynthetic flows are coupled to each other.4.Thermoluminescence, an index of oxygen evolution, was measured on G.violaceus. Its oscillation pattern showed the four-periodic change, as seen in other cyanobacteria, indicating the conserved reaction mechanism of water oxidation, four-step electron transfer.5.As revealed from genome sequence, G.vioalceus is unique in its properties of photosystem II, it seems convincing that transformation of this species will bring about many possible experiments for our understanding on the oxygen evolving system.

为了了解蓝藻中氧演化的分子机制及其从无氧光合细菌到蓝藻的演化过程，我们选择了一种独特的蓝藻物种Gloeobacter violaceus PCC 7421作为其原始特征的代表，即缺乏类囊体膜的蓝藻。首先，我们通过与Kazusa DNA研究所（DNA Res. 10,137,2003）的合作研究，确定了G.violcaeus的全基因组序列。基因组信息显示，该物种缺乏许多与光合作用和其他代谢途径相关的基因；例如，用A/B/C表示昼夜节律。我们试图构建这一物种的转化体系，但目前，我们还没有成功地开发该体系。坚硬的细胞壁可能是外源基因掺入的原因。我们直接评估了该物种的析氧特性。稳态析氧活性约为250 μmoleO2/mg Chl/hr，略低于Synechocystis sp.PCC 6803的稳态析氧活性。一个典型的特征是呼吸活性非常高，大约是聚囊藻sp.PCC 6803的10倍。这清楚地表明了紫花草中电子传递系统的不同，其中呼吸和光合流动是相互耦合的。用热释光法测定了紫花葡萄的释氧性能。其振荡模式与其他蓝藻一样，呈四周期变化，表明了水氧化的保守反应机制，即四步电子转移。从基因组序列中可以看出，g.v oalceus具有独特的光系统II特性，这一物种的转化将为我们对氧气进化系统的理解带来许多可能的实验。