Evolutionary History of Bioessential Elements Can Guide the Search for Life in the Universe

Abstract

Our understanding of life in the universe comes from one sample, life on Earth. Current and next-generation space missions will target exoplanets as well as planets and moons in our own solar system with the primary goal of detecting, interpreting and characterizing indications of possible biological activity. Thus, understanding life's fundamental characteristics is increasingly critical for detecting and interpreting potential biological signatures elsewhere in the universe. Astrobiologists have outlined the essential roles of carbon and water for life, but we have yet to decipher the rules governing the evolution of how living organisms use bioessential elements. Does the suite of life's essential chemical elements on Earth constitute only one possible evolutionary outcome? Are some elements so essential for biological functions that evolution will select for them despite low availability? How would this play out on other worlds that have different relative element abundances? When we look for life in the universe, or the conditions that could give rise to life, we must learn how to recognize it in extremely different chemical and environmental conditions from those on Earth. We argue that by exposing self-organizing biotic chemistries to different combinations of abiotic materials, and by mapping the evolutionary history of metalloenzyme biochemistry onto geological availabilities of metals, alternative element choices that are very different from life's present-day molecular structure might result. A greater understanding of the paleomolecular evolutionary history of life on Earth will create a predictive capacity for detecting and assessing life's existence on worlds where alternate evolutionary paths might have been taken.

Peptides before and during the nucleotide world: an origins story emphasizing cooperation between proteins and nucleic acids

“…A recent reconstruction of ancestral metalloenzymes [155] showed, paradoxically, a universal preference for Mo over Fe 2+ in nitrogen fixation, indicating that the selection of metal elements for proto-metalloenzyme catalysis might not be solely determined by global geochemical abundance, but also actively a consequence of selection for function [156]. Moreover, the local abundances of metals along with their interacting peptides vary between each niche environment and therefore drive different chemical reactions.…”

Reconstruction of Nitrogenase Predecessors Suggests Origin from Maturase-Like Proteins

“…Efforts to generate artificial nitrogenases and nitrogenase metalloclusters ( Tanifuji et al 2015 ; Sickerman et al 2017 ) may expand the suite of molecular structures capable of reducing N 2 , but biotic experiments integrating gene regulatory and protein–protein interaction constraints are needed to test different macroevolutionary hypotheses of nitrogenase emergence. A survey of such functional constraints on nitrogenase and maturase predecessors could reveal the sequence of biomolecular functions conducive for the evolution of nitrogen fixation, which could then be integrated into a more comprehensive accounting of internal selective forces, geochemical features, and planetary environments that can host similar evolutionary pathways ( Kacar et al 2021 ).…”

Reconstruction of nitrogenase predecessors suggests origin from maturase-like proteins

“…Efforts to generate artificial nitrogenases and nitrogenase metalloclusters (Tanifuji et al 2015;Sickerman et al 2017) may expand the suite of molecular structures capable of reducing N2, but biotic experiments integrating gene regulatory and protein-protein interaction constraints are needed to test different macroevolutionary hypotheses of nitrogenase emergence. A survey of such functional constraints on nitrogenase and maturase predecessors could reveal the sequence of biomolecular functions conducive for the evolution of nitrogen fixation, which could then be integrated into a more comprehensive accounting of internal selective forces, geochemical features and planetary environments that can host similar evolutionary pathways (Kacar et al 2020). Perhaps most intriguingly, our results suggest that nitrogen fixation may have emerged from natural selection acting on a maturase-like protein whose ancestral function was largely decoupled from extracellular conditions frequently implicated as drivers for the origins of nitrogen fixation.…”