Molecules to Microbes

Dear Colleagues,

A discussion meeting on the origin of life and life elsewhere in the Universe took place at the Eugenides Hall Foundation, in association with the National Technical University of Athens on 4th, 5th, and 6^th November 2018. This meeting is a biennial event that brings together scientists from different disciplines, including those who are not necessarily working directly on the questions of the origin of life. The reasoning behind this collaboration between scientists from “outside” and those directly involved in the origin of life sphere is that the question is just too darned difficult to answer, and this approach certainly maximises the array of perspective and input. How can this alliance help to answer these questions? This is best illustrated with an example; scientists (e.g., virologists) investigating the RNA viruses (primarily Retroviruses) discovered that the retroviral enzyme, reverse transcriptase (RT), can bring about the synthesis of DNA from an RNA template. It is inaccurate to describe RT as reverse, because the formation of DNA from an RNA is, in fact, a forward reaction as far as the origin of life is concerned, thus illustrating that DNA came after RNA—i.e., an RNA ‘invented’ DNA, also noting that DNA is primarily RNA without deoxy ribose sugar (as below) and methylated uracil base. The DNA synthesis reaction, in the presence of RT, could be more accurately written as RNA à DNA, and so it should be labelled forward transcriptase or real transcriptase, as announced by Professor Karin Moelling, a virologist, in her book (page 61) entitled “Viruses—More Friends than Foes” (2017). Moelling, who is a virologist turned advocate of the origin of life, is a typical example of an “outside” scientist.

The reason DNA came after RNA concerns ribose sugar and uracil. In RNA, ribose is a five-carbon “normal” sugar; in DNA, this sugar is deoxy, meaning that there is a conspicuous absence of the oxygen [O] atom at carbon atom number two (C2) in the pentose ring of ribose. There is no known natural mechanism by which [O] could be removed from the hydroxyl (OH) group at C2; this is because [O] is highly electronegative and is tightly bound to C2. Although it is possible to make 2-deoxyribose sugar experimentally from acetaldehyde and glyceraldehyde-5-phosphate, this is unlikely to have occurred in nature. The removal of [O] from the C2 hydroxyl group is still an open-ended question. The absence of [O] makes a DNA molecule more stable compared to an RNA molecule as a repository of genomes. So, it can be surmised that RNA with its hydroxylated C2 came first with DNA making its appearance later. The other difference—methylated uracil—is relatively easy to synthesise from uracil by adding methyl group (CH₃) to it.

To elucidate the exact routes of the emergence of life requires a multifaceted approach; that is, the input of scientists working in a wide spectrum of fields of research, including general practitioners in biology, chemistry, and physics; systems biology and chemistry; synthetics biology; virology pertaining to all three domains of life, including palaeontology and medical virologists; metagenomic and horizontal gene transfer specialists; pathogen scientists working with food poisoning microbes; bioinformatics; and geneticists. Scientists from these fields, as well as computer modelers and even mathematicians, are invited to submit articles of interest to this Special Issue.

Dr. Sohan Jheeta
Guest Editor

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