Influence of Taq DNA Polymerase in the Synthesis of Silico-Carbonates of Ca(II), Sr(II), and Ba(II): Implications on Biogenicity and Prebiotic Chemistry

Enzymes are seen as the link between chemistry and life; they replaced the initial work performed by RNA as the first catalyst, leading to the appearance of ribozymes. It has been proposed that prebiotic peptide synthesis occurs via multiple mechanisms. One plausible mechanism is that it happened in the prebiotic soup but a catalyst must have been present; otherwise, life would not have been possible, as shown by in vitro experiments. Although we do not have all of the information about the enzymes involved in the metabolism of the first life forms, there are currently extremophile microorganisms that live in extreme conditions like those of early organisms, such as during the Precambrian era. These microorganisms possess thermostable enzymes such as DNA polymerase from the bacterium Thermus aquaticus. Therefore, understanding how the first life forms could have originated in high-temperature extreme environments is crucial. The present work aims to evaluate the role of Taq DNA polymerase in synthesizing inorganic compounds from silico-carbonates of calcium, barium, or strontium (known as biomorphs) at high temperatures. The morphology of the synthesized biomorphs was observed using scanning electron microscopy (SEM). The micrographs showed that the presence of Taq DNA polymerase promotes the formation of spheres, regardless of the alkaline earth element used. The chemical composition and crystalline phases were determined by Raman and infrared spectroscopy and synchrotron X-ray diffraction (XRD). The analyses revealed that the calcium, barium, or strontium biomorphs are composed of crystalline material deposited on the surface of silicate films, forming silico-carbonates, such as calcite or vaterite (calcium), BaCO3 (witherite), or SrCO3 (strontianite), respectively. Our results demonstrate that Taq DNA polymerase is incorporated into the biomorph structure, forming spherical structures containing both mineral and organic phases, indicating that biomineralization occurs. These findings allow us to propose plausible pathways that played an essential role in the origin of life on Earth, suggesting that the mineral-organic phases that made up the proto-cell could be synthesized de novo in aqueous conditions likely present in the Precambrian. Finally, our current description is speculative because what seems to be feasible by prebiotic chemistry ideology does not seem to be compatible with those hypotheses that are biology-based. The opposite also holds true, such that notions of biological origins appear to be inconsistent with what prebiotic chemistry can provide.