Cyanide, a carbon atom bound to a nitrogen atom, is thought to be crucial for the origin of life. Scientists explore how we may be able to probe those deep waters from their expression on the surface. Hundreds of meters under the surface of a rocky valley in Oman, the sultanate on the south-eastern coast of the Arabian Peninsula, microbes are thriving even though there is no oxygen.
In the past, and in fact until quite recently, scientists thought that oxygen was vital for life, but unique habitats around the world are increasingly showing that life is more diverse than we initially expected — and might be found in many more places than had previously been assumed. The valley, known as the Semail Read More. How does it begin? Are we alone?
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The National Aeronautics and Space Administration NASA Astrobiology Institute NAI is hosting a virtual Workshop Without Walls on Astrovirology to review and advance the science of understanding what a virus is, their origin, ecology, impact on evolution, and their role in exobiology as a biosignature. This virtual workshop will be over two half-days to enabled global scientific exchange with no attendance costs or travel required. Topics covered will presented in a manner to reach a range of scientific understanding including students, researchers, educators, science A Rutgers-led study sheds light on one of the most enduring mysteries of science: How did metabolism — the process by which life powers itself by converting energy from food into movement and growth — begin?
Source: [ Rutgers Today ]. The surface of Titan has abundant carbon-rich molecules hydrocarbons that have been shown to form amino acids, the building blocks of proteins needed for life, when exposed to liquid water in laboratory simulations. Lake formation remains an open question in Titan science.
For example, a single galaxy, such as Andromeda, may contain over a trillion stars Mould, et al. However, this does not mean that all would have achieved life. Nevertheless, given even more extreme almost improbable odds of 1 in a sextillion trillion, it can be predicted that given over a sextillion trillion environments where trillions of chance combinations took place, then life could have arisen in multiple galaxies through chance combinations of the necessary ingredients in the womb of nebular clouds.
When we consider not just nebular clouds, but the vast number of planets and comets, some of which may have also contained all the necessary ingredients for generating life, extreme odds of up to sextillion trillion are no longer daunting. Therefore, it could be said that life may have have begun by 10 to 14 billion years ago, in this galaxy, perhaps right around the time or soon after this galaxy was formed 13 billion years ago.
On the other hand, although it takes at least 10 billion years to go from a single gene to a minimal gene set necessary for life, this does not mean that life began 10 billion years ago, but only that it takes at least 10 billion years. Again, the genetic analyses performed by Joseph, Sharov and Gordon did not include estimates as to the formation of the first proteins and nucleotides or the creation of the first DNA macro-molecule; and this leads us back to those estimates ranging from a trillion years to completely improbable.
However, if the universe is infinite the first gene and the first minimal gene set could have been established infinitely long ago. Life may have had no beginning, or the universe itself may be alive.
Or, as the atomists posited over two thousands years ago, within an infinite universe the atoms of life may continually assemble and reassemble over infinite time, such that, in the final analysis, life continually recycles itself, which means, life comes from life. Thus, after a trillion chance combinations in an ideal extraterrestrial environment, life was fashioned, and then diverged, and diverged again, giving rise to archae, bacteria, viruses, and Eukaryotes.
However, although there is substantial evidence that the co-mingling of Prokaryote and viral genes contributed to what became the multi-cellular Eukaryotic genome, there is no evidence that bacteria can become an archae or an archae a bacteria, or that a bacteria or a archae can become a Eukaryote. Rather, it took a commingling of genes from different species to form a multicellular Eukaryote. If life only began once in the vastness of the cosmos, how could it split up into three domains of life, two of which archae and bacteria are distinctly different, generally do not associate together, and often dwell in completely distinct environments?
Archae and bacteria are considered Prokaryotes. In the broadest terms, archaea are distinct from bacteria, particularly in regard to the size of their genomes and cell membranes. For example, archaean membranes are made of ether lipids whereas bacterial cell membranes are created from phosphoglycerides with ester bonds De Rosa et al. Like bacteria, archae can live in the most extreme environments Kimura et al, , ; Leininger et al. However, whereas bacteria are usually the most common form of life in the soil, archae are the most common form of life in the ocean, dominating ecosystems below m in depth Karner et al.
The genomes of archae are rather uniform and compact in size ranging from 0. Bacterial genomes can vary by two orders of magnitudes, from kb in the intracellular symbiont, Carsonella rudii Nakabachi et al. Although there are bacterial genomes of intermediate size, the vast majority of bacteria so far sequenced show a clear-cut bimodal distribution of genomes; i.
Although speculation abounds, there is no convincing evidence that archae and bacteria originated from a common ancestor which, in fact, has never been found. On the other hand, if that common ancestor dwells only in specific extraterrestrial environments, then perhaps the common ancestor to all of life will someday be discovered.
However, if life began multiple times or in multiple extraterrestrial locations, and if archae, bacteria, Eukaryotes and viruses have separate or even overlapping origins, why would the genetic code be similar, almost universal among all species, all domains of life, as well as viruses? Thus, where ever life is fashioned, be it in a primordial planet, a nebular cloud in another galaxy, a comet traveling through interstellar space, pre-life can only achieve life if it contains DNA and a genome with a minimal gene set.
Wallace coupled with endocytosis, phagocytosis, and horizontal gene transfer, that over billions of years extreme variations in genetic coding between innumerable microbial species were eventually averaged out; or that one genetic code won out as it was the superior code. Thus, initially, even if completely diverse life forms were generated in different extraterrestrial environments and with wildly different genetic codes, those codes may have become modified or extinguished upon encountering DNA-based life with a superior genetic code.
Through well established mechanisms of horizontal gene transfer Polz, et al. The superior code and its superior genes and genome then began dominating and taking over inferior genomes, thereby giving rise to a universal genetic code which is common to all life. If these latter propositions are true, then the different domains of life could have arisen in completely different extraterrestrial environments under localized conditions where all the essential ingredients were available for the manufacture of proteins, enzymes, DNA, RNA, the cell wall, membranes, etc.
Later, upon making contact, bacteria, archae, Eukaryotes, and viruses exchanged genes which resulted in a universal genetic code. And this is how life on Earth began. And then, it began to evolve. However, life was present on Earth from the very beginning, as demonstrated by discoveries of biological activity in the first rocks to re-solidify and harden, dated to 4. Additional evidence of life has been dated to 3. And this biological activity was most likely that of Cyanobacteria which is the only known species of Prokaryote capable of photosynthesis, and which also secretes oxygen and calcium.
In addition, microfossils resembling Eukaryotic yeast cells and fungi were discovered in 3.
Greenland Pflug It was during this same time period, 4. It can be deduced, therefore, that the first Earthlings arrived here within those meteors, asteroids and comets, and that Cyanobacteria were among these sojourners from the stars. And it can be concluded that the ancestors of these microbes and viruses hailed from space and with a genetic ancestry leading to planets much older than Earth. Viruses are found in association with and outnumber archae and bacteria on ratios ranging from 1 to 10, and 1 to respectively.
Thus, when viruses as well as Prokaryotes arrived on this planet in successive waves of invasion from space, they carried with them genes, and possibly entire genomes which had been acquired via horizontal gene transfer, from living creatures which had evolved on other worlds Joseph a, b,c,d. And once on Earth, these patterns of horizontal gene transfer continued, resulting in a co-mingling of genes which resulted in the generation of the first Earthly multi-cellular Eukaryotes.
Almost from the very beginning of the establishment of life on Earth, Prokaryotic archae and bacteria genes and viral genes were contributed to the Eukaryotic genome; and these donated genes have influenced and shaped the evolution of all subsequent multi-cellular species leading to humans.
They also terraformed the planet in preparation for those yet to evolve, and in so doing liberated minerals and released gases such as oxygen, which acted on those genes they had inserted into Eukaryotes. Prokaryotes Cyanobacteria in particular have biologically engineered this planet such as by pumping oxygen and calcium into the air and sea. And these genes, once embedded in the genomes of Eukaryotes, released pre-coded traits in response to the biologically engineered changing environment which enabled oxygen breathing animals to evolve hearts, bones and brains, then crawl upon the surface of the planet, walk on four then two legs, then stand upright and gaze into the heavens to ponder the nature of existence.
What has taken place on Earth is not a Darwinian evolution, but has unfolded according to the basic principles governing metamorphosis and embryogenesis and which resembles the precise, purposeful and genetically regulated interactions of those cells comprising a complex multi-cellular supra-organism.
Silent Genes, Horizontal Gene Transfer, Evolution Genomic analysis has demonstrated that genes are commonly shared between bacteria and archaea Koonin a,b; Polz et al , between Prokaryotes and Eukaryotes Hotopp et al. In fact, genes and entire chromosomes can be transferred between Eukaryotes including between humans Berger et al. The sharing of genes is accomplished via horizontal gene transfer HGT. However, although the transfer of genes between Eukaryotic genomes can provide benefits or protection Dhimolea et al.
Mutations do not contribute to the evolution of species. By contrast, genes transferred to the Eukaryotic genome by Prokaryotes and viruses, provide substantial benefits to the host and its genome.
Venturing into new realms? Microorganisms in space | FEMS Microbiology Reviews | Oxford Academic
Archae, bacteria, and viruses, provided Eukaryotes with the regulatory elements which control gene expression and which have repeatedly duplicated individual genes and the entire genome thereby enabling the Eukaryote gene pool to grow in size and leading to evolutionary innovation and the generation of increasingly intelligent species.
Thus we see that the genomes of modern day Eukaryotic species, including humans, contain highly highly conserved genes which were acquired from archae, bacteria, and viruses Esser et al. Viruses, as well as bacteria and archae, can also store their genes within the Eukaryotic genome Conley et al. The combination of these Prokaryote and viral genes therefore produced a new genome and a new species and possibly a new domain of life: Eukaryotes Feng et al. However if these combined genes generated the first unicellular Eukaryotes Woese or if single celled Eukaryotes were transformed into a multi-cellular Eukaryote after single celled Eukaryotes were first generated in their own unique extraterrestrial environment, is unknown.
Following successive invasions and combinations of Prokaryote and viral genes, some species of unicellular Eukaryotes became more diverse, and some of their descendants later came to be comprised of compartments and a nucleus which contains the DNA of multicellular Eukaryotes. Likewise, organelles, as well as mitochondria, may have been created following engulfment and the donation of bacterial and archae genes to the Eukaryotic host Dyall et al.
The incorporation of these Prokaryotic genes and the symbiotic relations which developed between Eukaryotes and genetically-stripped down bacteria and archae, led to the creation of the nucleus and compartmentalization.
The nucleus and compartmentalization made it possible for predatory Eukaryotes to ingest and phagocytize other creatures while minimizing the risk of random gene mixing and the unregulated incorporation of foreign DNA. Therefore, it appears the Eukaryotic nucleus was fashioned out of a Prokaryote which provided genomic protection, and this allowed other microbes to be safely ingested or incorporated thereby giving rise to additional compartments including the metamorphosis of mitochondria.
However, as the same time, these stripped down internalized Prokaryotes also allowed specific Prokaryote genes including viral genes and elements to be incorporated into the Eukaryotic genome following HGT. Therefore, Prokaryotes not only provided genes, compartments, and nuclei, but acted as gatekeepers which could determine which genes would be accepted and which would be rejected.
These developments enabled Eukaryotes to become more complex and conquer new environments which then acted on gene selection. When some single celled Eukaryotes acquired additional symbiotic partners and genes donated by archae, bacteria, and viruses, they became multi-cellular Joseph d, a. Therefore, the first multi-cellular Eukaryotes were fashioned via the combination of Prokaryotic and viral genes; an event which may commonly take place on every habitable planet.
Thus we see that the genomes of modern day Eukaryotic species, including humans, contain compartments, nuclei, mitochondria which appear to be stripped down Prokaryotes, and they contain highly conserved genes which were acquired from archae, bacteria, and viruses Esser et al.
However, not all of these genes have been expressed, whereas yet others have been activated in response to specific environmental signals, thereby giving rise to new species Joseph a, b,c. Archae, bacteria, and viruses, provided Eukaryotes with genes which code for core cellular functions including the regulatory elements which control gene expression and which have repeatedly duplicated individual genes and the entire genome. Individual and whole genome duplications have enabled the Eukaryote gene pool to grow in size thereby leading to evolutionary metamorphosis and the generation of increasingly complexand intelligent species, including humans.