{"id":2904,"date":"2010-12-06T08:00:07","date_gmt":"2010-12-06T06:00:07","guid":{"rendered":"http:\/\/localhost\/azgad\/wordpress\/?p=2904"},"modified":"2010-12-06T08:07:55","modified_gmt":"2010-12-06T06:07:55","slug":"follow-the-elements-%d7%94%d7%94%d7%95%d7%93%d7%a2%d7%94-%d7%94%d7%9e%d7%a7%d7%95%d7%a8%d7%99%d7%aa-%d7%a9%d7%9c-%d7%a0%d7%90%d7%a1%d7%90-%d7%91%d7%a2%d7%a0%d7%99%d7%99%d7%9f-%d7%94%d7%97%d7%99","status":"publish","type":"post","link":"https:\/\/azgad.com\/?p=2904","title":{"rendered":"Follow the Elements – \u05d4\u05d4\u05d5\u05d3\u05e2\u05d4 \u05e9\u05dc \u05e0\u05d0\u05e1"\u05d0 \u05d1\u05e2\u05e0\u05d9\u05d9\u05df \u05d4\u05d7\u05d9\u05d9\u05d3\u05e7 \u05de\u05d0\u05d2\u05dd \u05de\u05d5\u05e0\u05d5"},"content":{"rendered":"

.
\n\u05dc\u05d1\u05e7\u05e9\u05ea \u05db\u05de\u05d4 \u05e7\u05d5\u05e8\u05d0\u05d9\u05dd, \u05d4\u05e0\u05d4 \u05d4\u05d4\u05d5\u05d3\u05e2\u05d4 \u05d4\u05de\u05e7\u05d5\u05e8\u05d9\u05ea \u05e9\u05dc \u05e0\u05d0\u05e1"\u05d0 \u05d1\u05e2\u05e0\u05d9\u05d9\u05df \u05d4\u05d7\u05d9\u05d9\u05d3\u05e7 \u05de\u05d0\u05d2\u05dd \u05de\u05d5\u05e0\u05d5<\/strong>.
\n..
\nTEMPE, Ariz. \u2013 Evidence that the toxic element arsenic can
\nreplace the essential nutrient phosphorus in biomolecules of
\na naturally occurring bacterium expands the scope of the search
\nfor life beyond Earth, according to Arizona State University
\nscientists who are part of a NASA-funded research team
\nreporting findings in the Dec. 2 online Science Express.<\/p>\n

It is well established that all known life requires phosphorus,
\nusually in the form of inorganic phosphate. In recent years,
\n however, astrobiologists, including Arizona State University
\nprofessors Ariel Anbar and Paul Davies, have stepped up
\nconversations about alternative forms of life. Anbar and
\nDavies are coauthors of the new paper, along with ASU
\nassociate research scientist Gwyneth Gordon. The lead
\nauthor is Felisa Wolfe-Simon, a former postdoctoral scientist
\n in Anbar's research group at ASU's School of Earth and
\n Space Exploration and Department of Chemistry and
\nBiochemistry in the College of Liberal Arts and Sciences.
\n"Life as we know it requires particular chemical elements
\n and excludes others," says Anbar, a biogeochemist and
\nastrobiologist who directs the astrobiology program at ASU.
\n"But are those the only options? How different could life be?"
\nAnbar and Wolfe-Simon are among a group of researchers
\nwho are testing the limits of life's chemical requirements.
\n.
\n"One of the guiding principles in the search for life on other planets,
\n and of our astrobiology program, is that we should 'follow the
\nelements,'" says Anbar. "Felisa's study teaches us that we ought
\n to think harder about which elements to follow."
\n.
\nWolfe-Simon adds: "We took what we do know about the 'constants'
\n in biology, specifically that life requires the six elements CHNOPS
\n (carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur) in
\n three components, namely DNA, proteins and fats, and used
\nthat as a basis to ask experimentally testable hypotheses even
\n here on Earth."
\n.
\nFrom this viewpoint, rather than highlighting the conventional
\nview of the "diversity" of life, all life on Earth is essentially
\nidentical, she says. However, the microbe the researchers have
\ndiscovered can act differently.
\n.
\nDavies has previously speculated that forms of life different from
\nour own, dubbed "weird life," might even exist side-by-side with
\nknown life on Earth, in a sort of "shadow biosphere." The particular
\n idea that arsenic, which lies directly below phosphorous on the
\nperiodic table, might substitute for phosphorus in life on Earth,
\nwas proposed by Wolfe-Simon and developed into a collaboration
\n with Davies and Anbar. Their hypothesis was published in
\n January 2009, in a paper titled "Did nature also choose arsenic?"
\nin the International Journal of Astrobiology.
\n\/
\n"We not only hypothesized that biochemical systems analogous to
\nthose known today could utilize arsenate in the equivalent biological
\nrole as phosphate," notes Wolfe-Simon "but also that such
\norganisms could have evolved on the ancient Earth and might
\npersist in unusual environments today."
\n.
\nWolfe-Simon, now a NASA astrobiology research fellow in
\n residence at the U.S. Geological Survey, was one of the participants,
\nalong with Anbar, at a workshop titled "Tree or Forest? Searching
\nfor Alternative Forms of Life on Earth," that was organized in
\n December 2006 by the BEYOND Center, a "cosmic think tank"
\nat ASU.
\n.
\n"That's where it all began," says Davies, a cosmologist, astrobiologist,
\n theoretical physicist and director of the BEYOND Center.
\n.
\n"Felisa's talk was memorable for being a concrete proposal," Davies says.
\n "Many of the talks at the workshop discussed searching for radically
\nalternative forms of life with suggestions of the form 'maybe something
\n roughly like this,' or 'maybe a bit like that.' But Felisa said, quite
\nexplicitly, 'this is what we go look for.' And, she did."
\n.
\n"The idea was provocative, but it made good sense," notes Anbar.
\n"Arsenic is toxic mainly because its chemical behavior is so similar
\n to that of phosphorus. As a result, organisms have a hard time
\ntelling these elements apart. But arsenic is different enough that
\n it doesn't work as well as phosphorus, so it gets in there and sort
\nof gums up the works of our biochemical machinery."
\n.
\nAfter leaving ASU, Wolfe-Simon began a collaboration with Ronald
\n Oremland of the U.S. Geological Survey to chase down the
\nhypothesis. Oremland was a natural choice to bring into the project
\nbecause he is a world expert in arsenic microbiology. What
\nWolfe-Simon discovered is presented in the Science Express
\n paper titled "A bacterium that can grow by using arsenic
\n instead of phosphorus."
\nThe latest discovery is all about a bacterium \u2013 strain GFAJ-1
\nof the Halomonadaceae family of Gammaproteobacteria \u2013 scooped
\nfrom sediments of eastern California's Mono Lake, which is
\n extremely salty with naturally high levels of arsenic.
\n.
\nIn the laboratory, the researchers successfully grew microbes from
\nthe lake on a diet that was very lean on phosphorus, but included
\ngenerous helpings of arsenic.
\n.
\nKey issues that the researchers needed to address were the levels
\nof arsenic and phosphorus in the experiments and whether arsenic
\n actually became incorporated into the organisms' vital biochemical
\n machinery, such as DNA, proteins and the cell membranes. A
\nvariety of sophisticated laboratory techniques was used to nail
\ndown where the arsenic went, including mass spectrometry
\nmeasurements by Gordon at the W.M. Keck Foundation
\nLaboratory for Environmental Biogeochemistry at ASU.
\n.
\nCommenting on the significance of the discovery, Davies says:
\n"This organism has dual capability. It can grow with either
\nphosphorous or arsenic. That makes it very peculiar, though
\n it falls short of being some form of truly 'alien' life belonging
\nto a different tree of life with a separate origin. However, GFAJ-1
\n may be a pointer to even weirder organisms. The holy grail
\nwould be a microbe that contained no phosphorus at all."
\n.
\nDavies predicts that the new organism "is surely the tip of a big
\niceberg, and so has the potential to open up a whole new
\ndomain of microbiology."
\n.
\nIt is not only scientists, however, who will be interested in this
\n discovery. "Our findings are a reminder that life-as-we-know-it
\n could be much more flexible than we generally assume or can
\nimagine," says Wolfe-Simon, noting that because microbes are
\nmajor drivers of biogeochemical cycles and disease this study
\nmay open up a whole new chapter in biology textbooks.
\n.
\n"Yet, this story isn't about arsenic or Mono Lake," Wolfe-Simon
\n says. "If something here on Earth can do something so unexpected,
\nwhat else can life do that we haven't seen yet? Now is the time
\n to find out."
\n.<\/p>\n","protected":false},"excerpt":{"rendered":"

. \u05dc\u05d1\u05e7\u05e9\u05ea \u05db\u05de\u05d4 \u05e7\u05d5\u05e8\u05d0\u05d9\u05dd, \u05d4\u05e0\u05d4 \u05d4\u05d4\u05d5\u05d3\u05e2\u05d4 \u05d4\u05de\u05e7\u05d5\u05e8\u05d9\u05ea \u05e9\u05dc \u05e0\u05d0\u05e1"\u05d0 \u05d1\u05e2\u05e0\u05d9\u05d9\u05df \u05d4\u05d7\u05d9\u05d9\u05d3\u05e7 \u05de\u05d0\u05d2\u05dd \u05de\u05d5\u05e0\u05d5. .. TEMPE, Ariz. \u2013 Evidence that the toxic element arsenic can replace the essential nutrient phosphorus in biomolecules of a naturally occurring bacterium expands the scope of the search for life beyond Earth, according to Arizona State University scientists who are part … <\/p>\n

\u05d4\u05de\u05e9\u05d9\u05db\u05d5 \u05d1\u05e7\u05e8\u05d9\u05d0\u05d4<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[10],"tags":[336,313,513,337],"class_list":["post-2904","post","type-post","status-publish","format-standard","hentry","category-10","tag-336","tag-313","tag-513","tag-337","nodate","item-wrap"],"_links":{"self":[{"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts\/2904","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2904"}],"version-history":[{"count":9,"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts\/2904\/revisions"}],"predecessor-version":[{"id":2913,"href":"https:\/\/azgad.com\/index.php?rest_route=\/wp\/v2\/posts\/2904\/revisions\/2913"}],"wp:attachment":[{"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2904"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2904"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/azgad.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2904"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}