The thermodynamic efficiency of computations made in cells across the range of life
The thermodynamic efficiency of computations made in cells across the range of life
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DOI：
10.1098/rsta.2016.0343
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发表时间：
2017-12-28
期刊：
影响因子：
5
通讯作者：
Perez-Mercader, Juan
中科院分区：
文献类型：
--
作者：
Kempes, Christopher P.;Wolpert, David;Perez-Mercader, Juan
生物有机体必须在生长、繁殖和进化过程中进行计算。此外，自从朗道界限被提出以来，众所周知，所有的计算都有一定的热力学成本--同样的计算可以用更大或更小的热力学成本来实现，这取决于它的实现方式。因此，关于生命进化的一个重要问题是评估生物体进行的计算的热力学效率。这个问题很有趣，一方面是从生命如何接近最高效率计算的角度(想必是在自然选择的压力下)，另一方面是从实践的角度来看，我们可能希望工程生物计算机能达到什么效率，特别是与当前的计算系统相比。在这里，我们展示了平移的计算效率，定义为每一次氨基酸操作所消耗的自由能，其性能比最好的超级计算机高出几个数量级，并且仅比Landauer界限差一个数量级。然而，这种效率在很大程度上取决于相关单元的大小和架构。特别是，我们证明了氨基酸操作的有用效率，定义为每次氨基酸聚合的体积能量，随着细菌大小的增加而降低，并收敛于核糖体的聚合成本。随着我们向单细胞和多细胞真核生物的重大进化转变，最大细菌的这种成本在细胞中不会改变。然而，随着细胞大小的增加，细菌单位质量的总计算率是非单调的，并且在不同的生物结构中也是不同的，包括从单细胞真核生物到多细胞真核生物的转变。这篇文章是主题问题“重新概念化生命的起源”的一部分。
Biological organisms must perform computation as they grow, reproduce and evolve. Moreover, ever since Landauer's bound was proposed, it has been known that all computation has some thermodynamic cost-and that the same computation can be achieved with greater or smaller thermodynamic cost depending on how it is implemented. Accordingly an important issue concerning the evolution of life is assessing the thermodynamic efficiency of the computations performed by organisms. This issue is interesting both from the perspective of how close life has come to maximally efficient computation (presumably under the pressure of natural selection), and from the practical perspective of what efficiencies we might hope that engineered biological computers might achieve, especially in comparison with current computational systems. Here we show that the computational efficiency of translation, defined as free energy expended per amino acid operation, outperforms the best supercomputers by several orders of magnitude, and is only about an order of magnitude worse than the Landauer bound. However, this efficiency depends strongly on the size and architecture of the cell in question. In particular, we show that the useful efficiency of an amino acid operation, defined as the bulk energy per amino acid polymerization, decreases for increasing bacterial size and converges to the polymerization cost of the ribosome. This cost of the largest bacteria does not change in cells as we progress through the major evolutionary shifts to both single- and multicellular eukaryotes. However, the rates of total computation per unit mass are non-monotonic in bacteria with increasing cell size, and also change across different biological architectures, including the shift from unicellular to multicellular eukaryotes.This article is part of the themed issue 'Re-conceptualizing the origins of life'.