Origin of Life?

courtesy of dailygalaxy.com

There's a fascinating article in Nature (here's the article, courtesy of the University of Texas) on how life started on Earth, and the evidence in rRNA that suggests it came from deep hydrothermal vents in the ocean. The article here focuses on the similarities between the metabolism of autotrophs and the geochemical reactions that take place in the vents. The reactive gases, dissolved elements, the pH, and thermal gradients at the vents are suitable for the development of life. Given that the same type of environment was very common in early Earth's oceans, it is likely that the microbes that thrive at the vents could be closely related to the first microbes on Earth, despite oxic conditions and carbonate chimneys in modern vents. The vents in early Earth were anoxic, and were FeS-rich in comparison. Anaerobic methane-oxidizing microbes' biological pathways were compared to the geochemical process of serpentinization, where water and bicarbonate reduce Fe2+ in hydrothermially altered mantle rock to produce serpentine and hydrogen gas. Hydrogen gas is an electron source that can, in turn, reduce carbon dioxide to methane in a process similar to the biochemical pathways of local methane-oxidizing microbes. This comparison is important because if life did arise from systems like LCHF, serpentinization could have been an evolutionry precursor to the first biochemical pathways. To support the possibility of life originating at LCHF-like systems, the authors mentioned that the pH and thermal gradients at the LCHFs would allow high concentration of biological precursors to form, and that they could be used to explain the origins of chemiosmotic coupling in modern autotrophs. 


In contrast to the anoxic oceans of the Hadean era, today's oceans have plenty of oxygen. Thus the chemical of composition of the LCHFs and the vents would be different from the oceans of early Earth. The presence of oxygen means very different microbes would exist then, compared to now. How do aerobic microbes in the hydrothermal vents, figure in finding the origins of life? Are they of any special interest, or should further research focus on methanogens only? How did lipid bilayers, a sure prerequisite for life, come about? Most of the compounds discussed in the article are very simple and small.

Posted in: biology