Submitted:
12 June 2025
Posted:
16 June 2025
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Abstract

Keywords:
1. Introduction
2. Preprokaryotic Organismal Lifeforms Existing Today (POLET) Hypothesis
2.1. Longevity and Metabolic Quiescence
2.1.1. Lifespan Characteristics
2.2. Primitive Biochemistry and Genetic Mechanisms
2.2.1. Non-Enzymatic Catalysis
2.3. Reproductive Strategy
2.3.1. Blebbing over Binary Fission
2.4. Membrane Composition and Origin
2.4.1. Mineral-Assisted Membrane Assembly
2.5. Detectability of POLETicians
2.5.1. Analytical and Imaging Approaches
2.6. Ecological Niches and Interactions
2.6.1. Symbiotic Roles in Sediment Microbiomes
2.7. Alternative Energy Acquisition
2.7.1. Redox and Radiolytic Metabolism
2.8. Implications for the Search for Life
2.8.1. A Broader Framework for Life's Emergence
2.9. Redefining the Hallmarks of Life
2.9.1. Toward a POLET-Compatible Life Definition
2.8. Figure

2.9. Table
| Amino acid | Codon | PCodon | Anticodon | PAnticodon | Fiber Forming Potential | Notes | Refs. |
| L-Arg | CGG | 4.0 x 10-3 | CCG | 1 | Weakly with PEG-Q11 | Electrostatic repulsion may prevent stable fiber formation alone | [41] |
| L-Arg | CGA | 1 | UCG | 3.4 x 10-5 | weak | See above. | [41] |
| L-Gln | CAA | 0.16 | UUG | 1 | Amyloid fibers | PolyQ diseases | [42] |
| L-His | CAC | 0.40 | GUG | 6.4 x 10-8 | Has cell penetrating properties | Aggregate under certain pH conditions | [43] |
| L-Ile | AUU | 4.8 x 10-109 | AAU | 1 | -sheets and amyloids | Contributes to amyloid-like structures | [44] |
| L-Leu | CUA | 1 | UAG | 0.07 | -sheets | hydrophobic | |
| Phe | UUU | 1 | AAA | 0.047 | Nanotubes/fibers | Aromatic stacking | [45] |
| Phe | UUC | 1 | GAA | 2.2 x 10-4 | Nanotubes/fibers | π–π stacking drives aggregation | [45] |
| Trp | UGG | 1 | CCA | 5.5 x 10-13 | Forms nanostructured micelles | π–π stacking drives aggregation | [46] |
| Tyr | UAU | 0.10 | AUA | 2.4 x 10-5 | Fibrils | Forms fibrils via aromatic and hydrogen bonding interactions. | [45] |
| Tyr | UAC | 0.016 | GUA | 8.0 x 10-3 | Fibrils | See above | [45] |
3. Discussion
4. Conclusions
Funding
Acknowledgments
Conflicts of Interest
Abbreviations
| POLET | Precursors to the origin of life exist today |
| PPK | Pre-prokaryrotes |
| ESP | Eukaryotic Signature Proteins |
References
- MacLeod, F., et al., Asgard archaea: Diversity, function, and evolutionary implications in a range of microbiomes. AIMS Microbiol, 2019. 5(1): p. 48-61. [CrossRef]
- Spang, A., et al., Complex archaea that bridge the gap between prokaryotes and eukaryotes. Nature, 2015. 521(7551): p. 173-179. [CrossRef]
- Zaremba-Niedzwiedzka, K., et al., Asgard archaea illuminate the origin of eukaryotic cellular complexity. Nature, 2017. 541(7637): p. 353-358. [CrossRef]
- Fournier, G.P. and A.M. Poole, A Briefly Argued Case That Asgard Archaea Are Part of the Eukaryote Tree. Front Microbiol, 2018. 9: p. 1896. [CrossRef]
- Imachi, H., et al., Isolation of an archaeon at the prokaryote-eukaryote interface. Nature, 2020. 577(7791): p. 519-525. [CrossRef]
- Liu, Y., et al., Expanded diversity of Asgard archaea and their relationships with eukaryotes. Nature, 2021. 593(7860): p. 553-557. [CrossRef]
- Koonin, E.V. and A.S. Novozhilov, Origin and Evolution of the Universal Genetic Code. Annu Rev Genet, 2017. 51: p. 45-62. [CrossRef]
- Yarus, M., J.J. Widmann, and R. Knight, RNA-amino acid binding: a stereochemical era for the genetic code. J Mol Evol, 2009. 69(5): p. 406-29. [CrossRef]
- Monnard, P.A. and D.W. Deamer, Membrane self-assembly processes: steps toward the first cellular life. Anat Rec, 2002. 268(3): p. 196-207. [CrossRef]
- Schafer, G., M. Engelhard, and V. Muller, Bioenergetics of the Archaea. Microbiol Mol Biol Rev, 1999. 63(3): p. 570-620. [CrossRef]
- Cockell, C.S., et al., Interplanetary transfer of photosynthesis: an experimental demonstration of a selective dispersal filter in planetary island biogeography. Astrobiology, 2007. 7(1): p. 1-9. [CrossRef]
- Kawaguchi, Y., et al., The possible interplanetary transfer of microbes: assessing the viability of Deinococcus spp. under the ISS Environmental conditions for performing exposure experiments of microbes in the Tanpopo mission. Orig Life Evol Biosph, 2013. 43(4-5): p. 411-28. [CrossRef]
- Oh, J., et al., Structural basis of transcription recognition of a hydrophobic unnatural base pair by T7 RNA polymerase. Nat Commun, 2023. 14(1): p. 195.
- Wu, Y., et al., Transfer learning enables identification of multiple types of RNA modifications using nanopore direct RNA sequencing. Nat Commun, 2024. 15(1): p. 4049.
- Service, R.F., A big step toward mirror-image ribosomes. Science, 2022. 378(6618): p. 345-346.
- Xu, Y. and T.F. Zhu, Mirror-image T7 transcription of chirally inverted ribosomal and functional RNAs. Science, 2022. 378(6618): p. 405-412.
- Pech, A., et al., A thermostable d-polymerase for mirror-image PCR. Nucleic Acids Res, 2017. 45(7): p. 3997-4005.
- Lopez-Garcia, P. and D. Moreira, The Syntrophy hypothesis for the origin of eukaryotes revisited. Nat Microbiol, 2020. 5(5): p. 655-667.
- Wachtershauser, G., Before enzymes and templates: theory of surface metabolism. Microbiol Rev, 1988. 52(4): p. 452-84.
- Yousey, A.M., et al., Resurrected 'ancient' Daphnia genotypes show reduced thermal stress tolerance compared to modern descendants. R Soc Open Sci, 2018. 5(3): p. 172193. [CrossRef]
- Tamarit, D., et al., A closed Candidatus Odinarchaeum chromosome exposes Asgard archaeal viruses. Nat Microbiol, 2022. 7(7): p. 948-952. [CrossRef]
- Jaunmuktane, Z. and S. Brandner, Invited Review: The role of prion-like mechanisms in neurodegenerative diseases. Neuropathol Appl Neurobiol, 2020. 46(6): p. 522-545.
- Charras, G.T., A short history of blebbing. J Microsc, 2008. 231(3): p. 466-78.
- Hanczyc, M.M., S.M. Fujikawa, and J.W. Szostak, Experimental models of primitive cellular compartments: encapsulation, growth, and division. Science, 2003. 302(5645): p. 618-22.
- Koehbach, J., et al., MALDI TOF/TOF-Based Approach for the Identification of d- Amino Acids in Biologically Active Peptides and Proteins. J Proteome Res, 2016. 15(5): p. 1487-96. [CrossRef]
- Schaible, G.A., et al., Comparing Raman and NanoSIMS for heavy water labeling of single cells. bioRxiv, 2025.
- Weber, P.K., et al., The NanoSIMS-HR: The Next Generation of High Spatial Resolution Dynamic SIMS. Anal Chem, 2024. 96(49): p. 19321-19329. [CrossRef]
- Chari, A. and H. Stark, Prospects and Limitations of High-Resolution Single-Particle Cryo-Electron Microscopy. Annu Rev Biophys, 2023. 52: p. 391-411.
- Blackmond, D.G., The origin of biological homochirality. Cold Spring Harb Perspect Biol, 2010. 2(5): p. a002147. [CrossRef]
- Ozturk, S.F., et al., Origin of biological homochirality by crystallization of an RNA precursor on a magnetic surface. Sci Adv, 2023. 9(23): p. eadg8274.
- Jain, M., et al., Advances in nanopore direct RNA sequencing. Nat Methods, 2022. 19(10): p. 1160-1164. [CrossRef]
- Ellefson, J.W., et al., Synthetic evolutionary origin of a proofreading reverse transcriptase. Science, 2016. 352(6293): p. 1590-3.
- Nikoomanzar, A., et al., Engineering polymerases for applications in synthetic biology. Q Rev Biophys, 2020. 53: p. e8.
- Wang, Y., et al., Nanopore sequencing technology, bioinformatics and applications. Nat Biotechnol, 2021. 39(11): p. 1348-1365.
- Rang, F.J., W.P. Kloosterman, and J. de Ridder, From squiggle to basepair: computational approaches for improving nanopore sequencing read accuracy. Genome Biol, 2018. 19(1): p. 90.
- Bethge, L. and S. Vonhoff, Pegylation of RNA Spiegelmers by a Novel Widely Applicable Two-Step Process for the Conjugation of Carboxylic Acids to Amino-Modified Oligonucleotides. Curr Protoc Nucleic Acid Chem, 2020. 81(1): p. e109.
- Vater, A. and S. Klussmann, Toward third-generation aptamers: Spiegelmers and their therapeutic prospects. Curr Opin Drug Discov Devel, 2003. 6(2): p. 253-61.
- Blair, C.C., et al., Radiolytic hydrogen and microbial respiration in subsurface sediments. Astrobiology, 2007. 7(6): p. 951-70. [CrossRef]
- Pavlov, A.A., et al., Radiolytic Effects on Biological and Abiotic Amino Acids in Shallow Subsurface Ices on Europa and Enceladus. Astrobiology, 2024. 24(7): p. 698-709.
- Tarnas, J.D., et al., Earth-like Habitable Environments in the Subsurface of Mars. Astrobiology, 2021. 21(6): p. 741-756.
- Kelly, S.H., et al., Titrating Polyarginine into Nanofibers Enhances Cyclic-Dinucleotide Adjuvanticity in Vitro and after Sublingual Immunization. ACS Biomater Sci Eng, 2021. 7(5): p. 1876-1888. [CrossRef]
- Chiti, F. and C.M. Dobson, Protein misfolding, functional amyloid, and human disease. Annu Rev Biochem, 2006. 75: p. 333-66.
- Lee, H.J., et al., Polyhistidine facilitates direct membrane translocation of cell-penetrating peptides into cells. Sci Rep, 2019. 9(1): p. 9398.
- Maury, C.P., Self-propagating beta-sheet polypeptide structures as prebiotic informational molecular entities: the amyloid world. Orig Life Evol Biosph, 2009. 39(2): p. 141-50.
- Parween, S., et al., Self-assembled dipeptide nanotubes constituted by flexible beta-phenylalanine and conformationally constrained alpha,beta-dehydrophenylalanine residues as drug delivery system. J Mater Chem B, 2014. 2(20): p. 3096-3106.
- Chou, S., et al., Synthetic peptides that form nanostructured micelles have potent antibiotic and antibiofilm activity against polymicrobial infections. Proc Natl Acad Sci U S A, 2023. 120(4): p. e2219679120. [CrossRef]
- Pasteur, L., Researches on the molecular asymmetry of natural organic products. Alembic club reprints. 1906, Edinburgh: The Alembic Club ; Chicago : University of Chicago Press. 46 p.
- Vantomme, G. and J. Crassous, Pasteur and chirality: A story of how serendipity favors the prepared minds. Chirality, 2021. 33(10): p. 597-601. [CrossRef]
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