Critics raise doubts on NASAs arsenic bacteria

first_img Explore further A microscopic image of GFAJ-1 grown on arsenic. The findings reported last week, were that some bacteria (GFAJ-1) thrived when access to phosphate was removed and the bacteria were grown in a highly toxic culture rich is arsenate. The scientists suggested the bacteria thrived because they were able to replace phosphorus, which has always been thought vital to life, with arsenic, which is directly under it on the periodic table and has similar chemical properties. The researchers also suggested the bacteria were replacing phosphorus with arsenic within the bases that make up DNA. These findings, if correct, would mean the scientists had found a new form of life on Earth, and it would also re-write the guide book on the essential requirements for life to exist elsewhere.After the findings were published in Science, other scientists began immediately to express their doubts at the conclusions of the paper, with some even expressing the opinion the paper should not have been published at all. One of the critics was Dr. Alex Bradley, from Harvard University, who blogged that there were a number of problems with the research. Firstly, if arsenic had replaced phosphorus in the DNA the molecule would have broken into fragments when the DNA was placed in water, since the arsenic would have hydrolyzed, and yet it did not. Secondly, the paper showed there was a small amount of phosphorus in the medium and Bradley argued that even though small, this could have been enough, since bacteria metabolism is extremely efficient. Dr. Bradley also pointed out the bacteria live in Mono Lake, which is rich in arsenic but which also contains a higher concentration of phosphate than almost anywhere else on Earth, and this means there would be no selective pressure for a life based on arsenic to evolve. Dr. Bradley also suggested a mass spectrum of the DNA sequences would have shown whether or not the nucleotides contained arsenic in place of phosphorus, but this was not done.Another critic was University of British Columbia biologist Rosie Redfield, who reviewed the paper on her blog, and has more recently submitted a letter to the journal. Among her conclusions are that the paper “doesn’t present ANY convincing evidence that arsenic has been incorporated into DNA (or any other biological molecule).” She also writes: “If this data was presented by a PhD student at their committee meeting, I’d send them back to the bench to do more cleanup and controls.”Dr. Redfield also points out there was phosphate in the culture and that the authors did not calculate whether the amount of growth they saw in the arsenate-only medium could be supported by the phosphate present. She calculates on the blog that the growth of the bacteria is actually limited by the amount of phosphorus.Another point made by Redfield is that the arsenic bacteria were “like plump little corn kernels” and contain granules, which are usually produced by bacteria when they have ample supplies of carbon and energy sources but there are shortages of other nutrients needed for growth.The authors of the arsenic bacteria paper initially refused to be drawn into the arguments, saying the discussion should be confined to peer-reviewed journals, but one of the authors, Ronald Ormeland, did answer questions on the controversy after giving a lecture on the findings at NASA headquarters yesterday. He said the amount of phosphorus in the sample was too small to sustain growth, and a mass spectrum was not done because they did not have enough money, and wanted to get the result published quickly. He also pointed out that the bacteria are still there and other scientists could duplicate the work and carry out further experiments if they wished. (PhysOrg.com) — NASA’s announcement last week that bacteria had been discovered that appeared to replace phosphorus with arsenic and thrive even in the most poisonous environments, has now come under fire from a number of scientists. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.center_img © 2010 PhysOrg.com 3 Questions: Sara Seager on the discovery of a ‘new’ form of life Citation: Critics raise doubts on NASA’s arsenic bacteria (2010, December 9) retrieved 18 August 2019 from https://phys.org/news/2010-12-critics-nasa-arsenic-bacteria.htmllast_img read more

Best of Last Week—The Zeno effect selfdriving cars and the genetic impact

first_img And another team with the National Institute of Standards and Technology found a way to experimentally demonstrate a 140-year-old prediction: A gas in perpetual non-equilibrium. They created a 3-dimensional cloud that never reached thermal equilibrium. In a more practical effort, a team at Cambridge University announced that they had developed a new method for scaling up quantum devices—allowing for control of 14 quantum dots with just 19 wires. Also somewhat related, a team of researchers at Harvard announced an experiment showing that light can go infinitely fast with a new on-chip material—the first on-chip metamaterial with a refractive index of zero.In other news, a group of geochemists at UCLA found evidence that suggests life on Earth likely started 4.1 billion years ago—much earlier than scientists thought—by studying zircons in a lab. And a trio of researchers (Jean-François Bonnefon, Azim Shariff and Iyad Rahwan) uploaded a paper to the preprint server arXiv, each looking at the ethical issues of self-driving cars. Each poses questions meant to stir policymakers into thinking about self-driving cars under ethical scenarios. Also, a team of researchers at the University of Queensland found 1500 ‘ageing’ genes that could lead to new treatments—which they suggest might lead to new ways to treat old age-related ailments. And an international team of researchers made an unexpected discovery—a comet that contains alcohol and sugar—comet Lovejoy , which left evidence of its makeup as it swept past our field of view this past February.And finally, if you are male and have been stressing about the impact that stress may be having on your body, you may have even more to worry about as a team at the University of Pennsylvania found that stressed dads affect offspring brain development through sperm microRNA. (Phys.org)—It was another banner week for physics as one team at Cornell verified the ‘Zeno effect,’ whereby atoms won’t move while observed. They conducted experiments in an Ultracold Lab and found that atoms that normally would tunnel under a given circumstance, would not if they were watched. Also another international team of researchers found a way to experimentally realize a quantum Hilbert hotel—they made two proposals, one theoretical the other experimental, both of which were based on an infinite number of quantum states. Physicists experimentally realize a quantum Hilbert hotel When the light “petals” (quantum states with an infinite number of values representing the infinite number of hotel rooms) in the top row are multiplied by 3, the number of petals in the bottom row is tripled—analogous to “tripling infinity.” Credit: Václav Potoček, et al. ©2015 American Physical Society Journal information: arXiv Explore further © 2015 Phys.org Citation: Best of Last Week—The Zeno effect, self-driving cars and the genetic impact of stress on offspring (2015, October 26) retrieved 18 August 2019 from https://phys.org/news/2015-10-weekthe-zeno-effect-self-driving-cars.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more