The thermodynamic efficiency of computations made in cells across the range of life

Abstract

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 1 arXiv:1706.05043v1 [q-bio.OT] 15 Jun 2017 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 nonmonotonic in bacteria with increasing cell size, and also change across different biological architectures including the shift from unicellular to multicellular eukaryotes.

Semantic information, autonomous agency and non-equilibrium statistical physics

“…In particular, the fact that organisms must maintain themselves in a low entropy state was famously proposed, in an informal manner, by Schrödinger [82], as well as Brillouin [83] and others [84,85]. This had led to an important line of work on quantifying the entropy of various kinds of living matter [86][87][88][89]. However, this research did not consider the role of organism-environment information exchanges in maintaining the organism's low entropy state.…”

Multiverse Predictions for Habitability: Fraction of Planets that Develop Life

“…We have systematically combined the plate tectonics condition with all our previous habitability criteria to determine which combinations are consistent with the multiverse hypothesis. We report a few: if the yellow and entropy conditions are included along with the plate tectonics condition, we have the probabilities Ppα obs q " 0.064, Ppβ obs q " 0.38, Ppγ obs q " 0.20 (16) If we include the photosynthesis, entropy and tidal locking condition, we have Ppα obs q " 0.063, Ppβ obs q " 0.50, Ppγ obs q " 0.29 (17) This is not an exhaustive list: we are reaching a point where it becomes untenable to report every criterion in table format, even when restricting to those above some threshold, and so we will release the full list online as supplemental material at publication. Rather, these three representatives form germs: combinations of habitability criteria that all additional successful hypotheses will contain.…”

Thermodynamic efficiency of contagions: a statistical mechanical analysis of the SIS epidemic model

“…We specifically study the thermodynamic efficiency of contagion, considered as a distributed computational process. The thermodynamics of computation have recently been investigated in various contexts [18,[24][25][26][27][28], but have not been applied to studies of epidemics.…”