Crystallization of bacteria and archaea. (A) Woese’s model. Phylogenetic analysis of rDNA revealed three domains of life, Bacteria, Archaea, and Eucarya. (a) Symbiosis between Archaea and α-Proteobacteria could yield Eucarya (lower purple arrow). (b) Symbiosis between Eucarya and Cyanobacteria could yield Archaeplastida (upper purple arrow). The concepts in (a,b) were originally proposed by Margulis. Eukaryotic cells range in size from 5 to 100 µm. Woese proposed that the Bacteria and Archaea domains arose from the crystallization of systems in the LUCA. Moreover, the LUCA might be derived from a progenote descended from an RNA world. (B) Submarine alkaline vent model. (a) The emergence of free-living bacteria and archaea at an ancient submarine alkaline vent was described as a stepwise process. Koonin and Martin proposed that the LUCA was not a free-living cell. (b) Cartoon of a submarine alkaline vent. Extant vents as well as early vents have numerous honeycomb-like chambers with sizes of 1 to 100 µm (average 50 µm) [25]. E. coli (bacteria) is 3 µm long. (c) Steps proposed in the current study. We have previously proposed a hypothesis for the origin of the genetic code and evolution of the translation system. The order of events described in (B(a)) differs from that described in previous study (green background). In this study, we proposed evolutionary steps from the LUCA to bacteria and archaea at an ancient submarine alkaline vent (yellow background). — BIOLOGY — via PubMed
We propose a hypothesis for the simultaneous emergence of bacteria, archaea, viruses, and mobile elements by sequential and concrete biochemical pathways.
The emergence process can be considered analogous to crystallization, where genetic and biochemical systems stabilize as organisms evolve from their common ancestor, the LUCA, which was a non-free-living pool of single operon type genomes including double-stranded (ds) DNA at an ancient submarine alkaline vent.
Each dsDNA operon was transcribed by different systems in σ, TFIIB, or TBP genomes. Double-stranded DNA operons can fuse and stabilize through the action of specific transcription systems, leading to differentiation between the Bacteria (σ genome) and Archaea (TBP genome) domains. Error catastrophe can be overcome by the parallel gain of DNA replication and DNA repair mechanisms in both genomes.
Enlarged DNA enabled efficient local biochemical reactions. Both genomes independently recruited lipids to facilitate reactions by forming coacervates at the chamber of the vent. Bilayer lipid membrane formation, proto-cell formation with a permeable membrane, proto-cell division, and the evolution of membrane-associated biochemistry are presented in detail.
Simultaneous crystallization of systems in non-free-living bacteria and non-free-living archaea triggered the co-crystallization of primitive viruses and mobile elements. An arms race between non-free-living cells and primitive viruses finally led to free-living cells with a cell wall and mature viruses.
Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻
