Universal scaling across biochemical networks on Earth

Abstract

Attempts to identify universal properties of life are limited by the single example of biochemistry on Earth. Using a global database of 28,146 annotated genomes and metagenomes, we report universal scaling laws governing the topology of biochemical networks across levels of organization from individuals, to ecosystems, to the biosphere as a whole. We show the three domains of life are topologically distinguishable, while nonetheless conforming to the same universal scaling laws. Comparing real biochemical networks to networks composed of randomly sampled biochemical reactions reveals the observed scaling is not a product of shared biochemistry alone, but is instead attributable to universal constraints on how global biochemistry is partitioned into individuals. The reemergence of the same regularities across levels of organization hints at general principles governing biochemical network architecture.There is increasing interest in whether life has universal properties, not tied to its specific chemical instantiation (1). Universal biology, if it exists, would have important implications for constraining the origins of life, engineering synthetic life and guiding the search for life beyond Earth (2, 3). Systems biology provides promising tools for uncovering such general principles. One approach has been to study the topology of organismal metabolic networks, revealing common 'scale-free' structure for all three domains of life (4). Another approach is identification of scaling laws describing remarkable consistency in scaling of biomass, biodiversity, and metabolic rate (5-9). However, so far it has been difficult to unify these patterns across all levels of organization where living processes persist, from individuals to ecosystems to the biosphere. A more convincing case for universal biology would be made by demonstrating all life on Earth shares similar properties, independent of biochemical diversity or level of organization. Here we show biochemical networks conform to universal scaling laws governing their global topology, which tightly constrain not only the network structure of individuals, but also that of ecosystems and the biosphere as a whole.

Exoplanet Biosignatures: Future Directions

“…The universality of metabolic network organization suggests that life on other worlds might evolve to exhibit network topology similar to that of Earth's metabolic networks (Kim et al , 2018 ) and, therefore, that network topology is itself a biosignature. One hypothesis is that life could additionally leave a topological imprint on atmospheric chemistry.…”

Scarcity of scale-free topology is universal across biochemical networks

“…Nonetheless, the fact that multiple levels and multiple projections of biochemistry reveal common structure suggests universal principles may be within reach if cast within an ensemble theory of Sept. 2020 10/23 biochemical network organization (see e.g. also [36]).…”

“…In this way, biochemistry is hierarchically organized into individuals and ecosystems. Indeed, much discussion about universal properties of life has shifted focus from individuals to ecosystems as the relevant scale best capturing the regularities of biological organization [35,36]. It is unclear at present whether analysis of biochemical networks at the level of individuals or ecosystems will best uncover their structure and permit identifying generative mechanisms for biology, or whether all levels must be considered simultaneously.…”

Exoplanet Biosignatures: At the Dawn of a New Era of Planetary Observations

“…Given the continually evolving concepts of life, Walker et al approach Bayesian analysis as a means to incorporate additional types and novel concepts of life, and to organize new data and understanding as they become available (Kim et al, 2018 ). For the detection of biology that differs from that of Earth's, the Bayesian framework offers a means to integrate the languages of a diverse community, each having its own frontiers of knowledge and understanding.…”