The metabolic demands of endosymbiotic chemoautotrophic metabolism on host physiological capacities
The metabolic demands of endosymbiotic chemoautotrophic metabolism on host physiological capacities
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DOI：
10.1242/jeb.049023
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发表时间：
2011-01-01
影响因子：
2.8
通讯作者：
Girguis, P. R.
中科院分区：
文献类型：
--
作者：
Childress, J. J.;Girguis, P. R.
虽然热液喷口和其他还原环境的化学自养内共生已得到充分研究，但很少有人关注共生代谢对宿主的代谢需求的大小以及满足这些需求所需的适应。在这里，我们首次尝试进行这样的评估，并表明中等到高速率的化能自养或甲烷氧化代谢对宿主产生的摄氧量和质子当量消除要求远高于与其相关的非共生环节动物、双壳类和腹足类谱系的典型要求。描述并比较主机的属性，以确定哪些属性与最高速率相关并预测最高速率。我们认为这些共生体的高需氧量可能是共生体的最大限制通量。这种需求的后果之一是在这些共生体中广泛存在循环和/或组织血红蛋白，这是支持硫代自养型内共生体中高代谢率所必需的。我们还比较了光合自养与化能自养和甲烷氧化内共生，以评估生理学上的差异和相似之处。这些分析表明，化能自养共生体和甲烷氧化共生体对氧气的高需求可能是阻止它们与刺胞动物内共生的主要因素。
While chemoautotrophic endosymbioses of hydrothermal vents and other reducing environments have been well studied, little attention has been paid to the magnitude of the metabolic demands placed upon the host by symbiont metabolism and the adaptations necessary to meet such demands. Here we make the first attempt at such an evaluation, and show that moderate to high rates of chemoautotrophic or methanotrophic metabolism impose oxygen uptake and proton equivalent elimination demands upon the hosts that are much higher than is typical for the non-symbiotic annelid, bivalve and gastropod lineages to which they are related. The properties of the hosts are described and compared to determine which properties are associated with and predictive of the highest rates. We suggest that the high oxygen demand of these symbionts is perhaps the most limiting flux for the symbioses. Among the consequences of such demands has been the widespread presence of circulating and/or tissue hemoglobins in these symbioses that are necessary to support high metabolic rates in thioautotrophic endosymbioses. We also compare photoautotrophic with chemoautotrophic and methanotrophic endosymbioses to evaluate the differences and similarities in physiologies. These analyses suggest that the high demand for oxygen by chemoautotrophic and methanotrophic symbionts is likely a major factor precluding their endosymbiosis with cnidarians.