Aspects of the relation between Cyanophora paradoxa (Korschikoff) and its endosymbiotic cyanelles Cyanocyta korschikoffiana (Hall & Claus) - I. Growth, ultrastructure, photosynthesis and the obligate nature of the association
Aspects of the relation between Cyanophora paradoxa (Korschikoff) and its endosymbiotic cyanelles Cyanocyta korschikoffiana (Hall & Claus) - I. Growth, ultrastructure, photosynthesis and the obligate nature of the association
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Cyanophora paradoxa (Korschikoff) 与其内共生氰藻 Cyanocyta korschikoffiana (Hall) 之间的关系
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发表时间：
1978
期刊：
影响因子：
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通讯作者：
A. Engelland
中科院分区：
文献类型：
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作者：
R. Trench;R. R. Pool;M. Logan;A. Engelland
超微结构研究表明，内生共生蓝藻存在于宿主细胞液泡中，具有高度缩小的原核细胞壁，在二次分裂过程中尤为明显。内共生蓝藻的分裂与寄主隐单胞菌的分裂不同步。当宿主种群达到其渐近线时，蓝藻分裂最快，因此，在延长静止期的培养中，在一个宿主细胞中可以观察到多达8个蓝藻。从营养上讲，异花梭子藻被发现是一种专性的光生生物；它的辅助作用仅限于乙酸盐和氰基钴胺。光合作用速率分析表明，在140molCO2·cm~(-2)·S~(-1)处达到饱和，饱和光强下的固定速率为30μ·μ·CO_2(Mg Chla)~(-1)·h~(-1)。分离的蓝藻获得的最好的二氧化碳固定率是完整组合中的12%。两种独立的分析方法表明，充其量只有15%的被蓝藻固定的碳被转移到宿主体内，主要是葡萄糖和可能的蔗糖。针对原核蓝藻的代谢抑制剂研究表明，宿主与内共生菌之间存在着密切的相互依赖关系，内共生菌的破坏往往会导致宿主的死亡。我们无法将蓝藻从宿主中培养出来，再加上宿主显然无法在没有光合作用的内共生蓝藻的情况下生存，这有力地支持了这种联系代表着一种很好地整合的相互约束关系的概念，但不能支持蓝藻是叶绿体的概念。
Ultrastructural studies of the symbiotic relation between the apochlorotic cryptomonad Cyanophora paradoxa and the cyanobacterium Cyanocyta korschikoffiana have demonstrated that the endosymbiotic cyanobacteria are within host cell vacuoles and possess a highly reduced prokaryotic cell wall which becomes particularly evident during binary fission. Division by the endosymbiotic cyanobacteria was found not to be in synchrony with division by the host cryptomonad. The cyanobacteria divided most rapidly when the host population had reached its asymptote, such that, in cultures in extended stationary phase, it is possible to observe as many as eight cyanobacteria in one host cell. Nutritionally, C. paradoxa was found to be an obligate phototroph; its auxotropic capabilities are confined to acetate and cyanocobalamin. Analysis of the rate of photosynthesis by the intact association demonstrated that saturation occurred at the 140 μE cm-2 s-1 (where E is einstein), and at saturating light intensities, the rate of CO2 fixation was 30 μmol CO2 (mg chl a)-1 h-1. The best rate of CO2 fixation obtained by the isolated cyanobacteria represented 12% of the rate found in the intact association. Two independent methods of analysis showed that at best, only 15% of the carbon fixed by the cyanobacteria was translocated to the host, mostly as glucose and probably sucrose. Studies with metabolic inhibitors directed against the prokaryotic cyanobacteria demonstrated the close interdependence of the host with the endosymbionts, in that disruption of the endosymbionts always resulted in death of the host. Our inability to grow the cyanobacteria away from the host, combined with the apparent inability of the host to survive in the absence of the photosynthetic endosymbiotic cyanobacteria provide strong support for the concept that the association represents a well integrated mutually obligate relation, but the concept that the cyanobacteria are chloroplasts cannot be supported.