|Year : 2013 | Volume
| Issue : 3 | Page : 73-74
Tooth structure at noncarbon-based-life: Is it a scientific topic?
Jafar Kolahi1, Yadolah Soleymani Shayesteh2
1 Independent Research Scientist, Founder and Managing Editor of Dental Hypotheses, Tehran University of Medical Sciences, Tehran, Iran
2 Department of Periodontics and Implant, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
|Date of Web Publication||8-Aug-2013|
No 24, Faree 15, Pardis, ShahinShahr, Isfahan 83179-18981
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Kolahi J, Shayesteh YS. Tooth structure at noncarbon-based-life: Is it a scientific topic?. Dent Hypotheses 2013;4:73-4
Following publication of our previous editorial "What would be the tooth structure at noncarbon-based-life?"  I have received several personal comments on this topic. They generally have criticism about scantiness of this topic. At first, I would like to emphasize that it is aim of Dental Hypotheses to publish new, challenging, radical, and nonmain stream scientific ideas so long as they are coherent and clearly expressed.  Most dental journals will publish ideas only in papers which also report observations. As the best scientists have repeatedly emphasized, this gives a misleading impression of the process of discovery. Dental Hypotheses can, therefore, form a bridge between cutting edge theory and the mainstream of dental scientific communication, which ideas must eventually enter if they are to be critiqued and tested against observations. This also means that we encourage authors to take responsibility for their ideas. Second, I would like to express same examples from most prestige scientific publications.
Some years ago, a challenging paper "A bacterium that can grow by using arsenic instead of phosphorus,"  was published at Science which is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals ( http://en.wikipedia.org/wiki/Science_(journal) ). This special bacteria, GFAJ-1 [Figure 1], is a strain of rod-shaped bacteria in the family Halomonadaceae. The extremophile was isolated from the hypersaline and alkaline Mono Lake in eastern California by a research team led by NASA astrobiologist Felisa Wolfe-Simon. The authors claimed that the microbe, when starved of phosphorus, is capable of substituting arsenic for a small percentage of its phosphorus and sustain its growth. Immediately after publication, other microbiologists and biochemists expressed doubt about this claim which was robustly criticized in the scientific community. Subsequent independent studies published in 2012 found no detectable arsenate in the DNA of GFAJ-1, refuted the claim, and demonstrated that GFAJ-1 is simply an arsenate-resistant, phosphate-dependent organism.  As you see arsenic-based life discussed in top scientific journals such as Science and well-known scientific organization such as NASA.
Moreover, the National Academy of Sciences has several publication regarding possibility of undiscovered noncarbon-based-life. For example "The limits of organic life in planetary systems."  At this interesting book, the following items were discussed: A sketch of the chemistry behind known carbon-based life on earth, pushing the boundaries of life, alternatives to terran biochemistry in water. The committee's investigation makes clear that life is possible in forms different from those on Earth. Different specific biomolecules may be considered highly likely in extraterrestrial life. Different architectures at the microscopic and macroscopic levels must also be considered likely. Advocates of replicator-first theories hold that-with reasonable interactions between minerals, polar refractory solvents, and organic species-the spontaneous emergence of genetic biopolymers may be expected. Other scientists feel that the chances of such an event are infinitesimal but that other circumstances may suffice for the origin of life. Whichever group is correct, the likelihood of encountering some form of life in subsurface Mars and sub-ice Europa appears high. Life-detection strategies should be redesigned to maximize the possibility of successful detection of life by seeking intermediates common to the two theories. 
Furthermore, life should be considered possible in aqueous environments that are extreme in their solute content, in their acidity or alkalinity, and in their temperature range, especially with ammonia as an antifreeze in low-temperature water-ammonia eutectics. The committee sees no reason to exclude the possibility of life in environments as diverse as the aerosols above Venus and the water-ammonia eutectics of Titan. It seems that life is less likely in more exotic solvents-such as liquid dinitrogen, liquid methane, and supercritical dihydrogen-but this conclusion is based on few data. 
It is clear that theoretical biochemistry and noncarbon-based-life are hot and fast growing scientific topics. Given the importance of developing the understanding and capability to detect and recognize possible life forms in other planetary environments, it is our duty to bring these topics to dental sciences and discuss about tooth structure and oral biology at noncarbon-based-life.
| References|| |
|1.||Kolahi J, Shayesteh YS. What would be the tooth structure at non-carbon-based-life? Dent Hypotheses 2013;4:37-8. |
|2.||Rossomando EF. Welcome to tomorrow. Dent Hypotheses 2010;1:1-3. |
|3.||Wolfe-Simon F, Switzer Blum J, Kulp TR, Gordon GW, Hoeft SE, Pett-Ridge J, et al. A bacterium that can grow by using arsenic instead of phosphorus. Science 2011;332:1163-6. |
|4.||GFAJ-1. Wikipedia, the free encyclopedia. Available from: http://en.wikipedia.org/wiki/GFAJ-1 [Last accessed on 2013 Jun 21]. |
|5.||Committee on the Limits of Organic Life in Planetary Systems, Committee on the Origins and Evolution of Life, National Research Council. The Limits of Organic Life in Planetary Systems. National Academy of Sciences. Available from: http://www.nap.edu/catalog/11919.html [Last accessed on 2013 Jun 21]. |