{"id":131698,"date":"2010-12-04T04:10:46","date_gmt":"2010-12-04T03:10:46","guid":{"rendered":"http:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/?p=131698"},"modified":"2010-12-06T00:02:21","modified_gmt":"2010-12-05T23:02:21","slug":"la-bacteria-amante-del-arsenico","status":"publish","type":"post","link":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/2010\/12\/04\/131698","title":{"rendered":"La bacteria amante del ars\u00e9nico…"},"content":{"rendered":"

\u00bfRecuerdan aquella frase hist\u00f3rica de la pel\u00edcula \u201cParque Jur\u00e1sico<\/a>\u201d que ven\u00eda a decir que \u201cla vida siempre se abre camino\u201d? Pues bien, de corroborarse, confirmarse, contrastarse y reproducirse los resultados que acaba de publicar la versi\u00f3n digital de Science<\/a><\/em>, dicha frase lapidaria cobrar\u00e1 una dimensi\u00f3n hiperrealista…<\/p>\n

\"Bacterias<\/a>
Bacterias en ars\u00e9nico<\/figcaption><\/figure>\n

Existe en la naturaleza una serie de organismos \u201cvivos\u201d \u2013as\u00ed dejamos en la cuneta a los virus<\/a>– capaces de vivir y reproducirse en condiciones verdaderamente extremas. Sin ir m\u00e1s lejos, en el entorno onubense m\u00e1s propio de Marte que de la Tierra, constituido por las minas de R\u00edo Tinto<\/a>, existen bacterias, como la conocida acid\u00f3fila Thiobacillus ferrooxidans<\/a>,<\/em> capaces de obtener energ\u00eda de la pirita produciendo en el proceso directamente \u00e1cido sulf\u00farico. Sea como fuere, una constante universal abarcaba todo el espectro biol\u00f3gico: la presencia del ADN<\/a> como mol\u00e9cula poseedora de toda la informaci\u00f3n vital: la informaci\u00f3n gen\u00e9tica. Este ADN es un pol\u00edmero de nucle\u00f3tidos<\/a>, es decir, una cadena de mol\u00e9culas formadas por un az\u00facar, una base nitrogenada y, uniendo mon\u00f3meros entre s\u00ed, un grupo fosfato. Esto constituye, en biolog\u00eda, una verdad universal; \u00bfo no?<\/p>\n

\"R\u00edo
R\u00edo Tinto<\/figcaption><\/figure>\n

Desde hace unas horas, la revista Science<\/a><\/em> publica los resultados obtenidos por Felisa Wolfe-Simon<\/a> y colaboradores del Instituto de Astrobiolog\u00eda de la NASA<\/a> con una extra\u00f1a proteobacteria<\/a> que es capaz, no ya de metabolizar, alimentarse o sobrevivir a base de ars\u00e9nico<\/a> \u2013como hacen otros microorganismos- sino, y esto es monstruosamente sorprendente, sustituir al f\u00f3sforo<\/a> de todas sus funciones celulares, incluyendo la de nexo de uni\u00f3n en los \u00e1cidos nucleicos.<\/p>\n

\"Bacterias<\/a>
Bacterias GFAJ-1<\/figcaption><\/figure>\n

Existe una gran similitud qu\u00edmica entre el ars\u00e9nico y el f\u00f3sforo. El primero se sit\u00faa justamente debajo del segundo en la tabla peri\u00f3dica. Sin embargo, no hay que confundirse. El ars\u00e9nico pertenece a los semimetales y es altamente t\u00f3xico \u2013disuelto en agua<\/a>, por encima de los 10 microgramos por litro, seg\u00fan se\u00f1ala la OMS, es perjudicial para la salud-, mientras que el f\u00f3sforo es un no metal indispensable para la vida, como ya se ha comentado. No obstante, el ars\u00e9nico puede, al menos in vitro,<\/em> sustituir parcialmente al f\u00f3sforo en reacciones bioqu\u00edmicas \u2013incluso lleg\u00f3 a ser, el ars\u00e9nico, en peque\u00f1as dosis, muy popular en medicina hasta finales del siglo XVIII<\/a>.<\/p>\n

Volviendo al art\u00edculo de la ocean\u00f3grafa convertida en astrobi\u00f3loga Wolfe-Simon, la nueva bacteria \u2013cepa GFAJ-1<\/a>– ha sido descubierta en el lago Mono<\/a> de California -lago supersalado del condado norteamericano del mismo nombre-. Es un miembro de la familia Halomonadaceae<\/em><\/a> dentro de las proteobacterias \u2013 uno de los principales y mayores grupos de bacterias, las proteobacterias<\/a>, que incluyen a miembros tan conocidos como la ubicua Escherichia, Vibrio <\/em>o Salmonella<\/em>, entre otros muchos g\u00e9neros. Esta nueva bacteria es capaz de crecer en el laboratorio en concentraciones crecientes de ars\u00e9nico donde se iba disminuyendo paulatinamente la concentraci\u00f3n de fosfato hasta conseguirse el milagro: el ars\u00e9nico sustituye a dicho fosfato<\/a> en todas las mol\u00e9culas biol\u00f3gicas como l\u00edpidos, prote\u00ednas y, sorprendentemente, el ADN. El seguimiento del ars\u00e9nico, desde su captura por la c\u00e9lula hasta su incorporaci\u00f3n \u00faltima en las macromol\u00e9culas no deja lugar a dudas: estamos, seg\u00fan se anunci\u00f3 en rueda de prensa mundial organizada por la NASA<\/a>, ante un verdadero hito hist\u00f3rico que probablemente cambie el concepto de la filogenia a lo largo de la evoluci\u00f3n y permitir\u00e1 abrir las rigurosas mentes cient\u00edficas hacia otras posibilidades de vida basadas en mol\u00e9culas distintas a las observadas hasta la fecha ya, incluso, sin necesidad de salir de nuestra peque\u00f1a Aldea. Por ello, aquella despedida gal\u00e1ctica de ciertas series televisivas fant\u00e1sticas, \u201cthe truth is out there<\/a><\/em>\u201d, cobra una nueva dimensi\u00f3n.<\/p>\n

\"Lago
Lago Mono<\/figcaption><\/figure>\n

JAL<\/a> -(CBMSO<\/a>)<\/p>\n

\u00a0<\/p>\n

\u00a0Debate con los autores<\/a>:<\/strong><\/p>\n

It is well established that all known life requires phosphorus, usually in the form of inorganic phosphate. In recent years, however, astrobiologists, including Arizona State University professors Ariel Anbar and Paul Davies, have stepped up conversations about alternative forms of life. Anbar and Davies are coauthors of the new paper, along with ASU associate research scientist Gwyneth Gordon. The lead author is Felisa Wolfe-Simon, a former postdoctoral scientist in Anbar’s research group at ASU’s School of Earth and Space Exploration and Department of Chemistry and Biochemistry in the College of Liberal Arts and Sciences.<\/p>\n

\u00abLife as we know it requires particular chemical elements and excludes others,\u00bb says Anbar, a biogeochemist and astrobiologist who directs the astrobiology program at ASU. \u00abBut are those the only options? How different could life be?\u00bb Anbar and Wolfe-Simon are among a group of researchers who are testing the limits of life’s chemical requirements.<\/p>\n

\u00abOne of the guiding principles in the search for life on other planets, and of our astrobiology program, is that we should ‘follow the elements,'\u00bb says Anbar. \u00abFelisa’s study teaches us that we ought to think harder about which elements to follow.\u00bb<\/p>\n

Wolfe-Simon adds: \u00abWe took what we do know about the ‘constants’ in biology, specifically that life requires the six elements CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur) in three components, namely DNA, proteins and fats, and used that as a basis to ask experimentally testable hypotheses even here on Earth.\u00bb<\/p>\n

>From this viewpoint, rather than highlighting the conventional view of the \u00abdiversity\u00bb of life, all life on Earth is essentially identical, she says. However, the microbe the researchers have discovered can act differently.<\/p>\n

Davies has previously speculated that forms of life different from our own, dubbed \u00abweird life,\u00bb might even exist side-by-side with known life on Earth, in a sort of \u00abshadow biosphere.\u00bb The particular idea that arsenic, which lies directly below phosphorous on the periodic table, might substitute for phosphorus in life on Earth, was proposed by Wolfe-Simon and developed into a collaboration with Davies and Anbar. Their hypothesis was published in January 2009, in a paper titled \u00abDid nature also choose arsenic?\u00bb in the International Journal of Astrobiology.<\/p>\n

\u00abWe not only hypothesized that biochemical systems analogous to those known today could utilize arsenate in the equivalent biological role as phosphate,\u00bb notes Wolfe-Simon \u00abbut also that such organisms could have evolved on the ancient Earth and might persist in unusual environments today.\u00bb<\/p>\n

Wolfe-Simon, now a NASA astrobiology research fellow in residence at the U.S. Geological Survey, was one of the participants, along with Anbar, at a workshop titled \u00abTree or Forest? Searching for Alternative Forms of Life on Earth,\u00bb that was organized in December 2006 by the BEYOND Center, a \u00abcosmic think tank\u00bb at ASU.<\/p>\n

\u00abThat’s where it all began,\u00bb says Davies, a cosmologist, astrobiologist, theoretical physicist and director of the BEYOND Center.<\/p>\n

\u00abFelisa’s talk was memorable for being a concrete proposal,\u00bb Davies says. \u00abMany of the talks at the workshop discussed searching for radically alternative forms of life with suggestions of the form ‘maybe something roughly like this,’ or ‘maybe a bit like that.’ But Felisa said, quite explicitly, ‘this is what we go look for.’ And, she did.\u00bb<\/p>\n

\u00abThe idea was provocative, but it made good sense,\u00bb notes Anbar. \u00abArsenic is toxic mainly because its chemical behavior is so similar to that of phosphorus. As a result, organisms have a hard time telling these elements apart. But arsenic is different enough that it doesn’t work as well as phosphorus, so it gets in there and sort of gums up the works of our biochemical machinery.\u00bb<\/p>\n

After leaving ASU, Wolfe-Simon began a collaboration with Ronald Oremland of the U.S. Geological Survey to chase down the hypothesis. Oremland was a natural choice to bring into the project because he is a world expert in arsenic microbiology. What Wolfe-Simon discovered is presented in the Science Express paper titled \u00abA bacterium that can grow by using arsenic instead of phosphorus.\u00bb<\/p>\n

The latest discovery is all about a bacterium \u2013 strain GFAJ-1 of the Halomonadaceae family of Gammaproteobacteria \u2013 scooped from sediments of eastern California’s Mono Lake, which is extremely salty with naturally high levels of arsenic.<\/p>\n

In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic.<\/p>\n

Key issues that the researchers needed to address were the levels of arsenic and phosphorus in the experiments and whether arsenic actually became incorporated into the organisms’ vital biochemical machinery, such as DNA, proteins and the cell membranes. A variety of sophisticated laboratory techniques was used to nail down where the arsenic went, including mass spectrometry measurements by Gordon at the W.M. Keck Foundation Laboratory for Environmental Biogeochemistry at ASU.<\/p>\n

Commenting on the significance of the discovery, Davies says: \u00abThis organism has dual capability. It can grow with either phosphorous or arsenic. That makes it very peculiar, though it falls short of being some form of truly ‘alien’ life belonging to a different tree of life with a separate origin. However, GFAJ-1 may be a pointer to even weirder organisms. The holy grail would be a microbe that contained no phosphorus at all.\u00bb<\/p>\n

Davies predicts that the new organism \u00abis surely the tip of a big iceberg, and so has the potential to open up a whole new domain of microbiology.\u00bb<\/p>\n

It is not only scientists, however, who will be interested in this discovery. \u00abOur findings are a reminder that life-as-we-know-it could be much more flexible than we generally assume or can imagine,\u00bb says Wolfe-Simon, noting that because microbes are major drivers of biogeochemical cycles and disease this study may open up a whole new chapter in biology textbooks.<\/p>\n

\u00abYet, this story isn’t about arsenic or Mono Lake,\u00bb Wolfe-Simon says. \u00abIf something here on Earth can do something so unexpected, what else can life do that we haven’t seen yet? Now is the time to find out.\u00bb<\/p>\n

###<\/p>\n

Other authors of the new study published in Science Express include Jodi Switzer Blum, Thomas Kulp and Shelly Hoeft, USGS; Jennifer Pett-Ridge and Peter Weber, Lawrence Livermore National Laboratory; John Stolz, Duquesne University; and Samuel Webb, Stanford Synchrotron Radiation Lightsource.<\/p>\n

This study was funded in part by NASA’s Astrobiology Program. Wolfe-Simon, Anbar, Davies and Oremland are members of the NASA Astrobiology Institute \u00abFollow the Elements\u00bb team at Arizona State University.<\/p>\n

\u00a0<\/strong><\/p>\n

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FACEBOOK<\/a>\u00a0<\/p>\n

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\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

\u00bfRecuerdan aquella frase hist\u00f3rica de la pel\u00edcula \u201cParque Jur\u00e1sico\u201d que ven\u00eda a decir que \u201cla vida siempre se abre camino\u201d? Pues bien, de corroborarse, confirmarse, contrastarse y reproducirse los resultados que acaba de publicar la versi\u00f3n digital de Science, dicha frase lapidaria cobrar\u00e1 una dimensi\u00f3n hiperrealista… Existe en la naturaleza una serie de organismos \u201cvivos\u201d \u2013as\u00ed dejamos en la cuneta a los virus– capaces de vivir y reproducirse en condiciones verdaderamente extremas. Sin ir m\u00e1s lejos, en el entorno onubense m\u00e1s propio de Marte que de la Tierra, constituido por las minas de R\u00edo Tinto, existen bacterias, como la conocida\u2026<\/p>\n","protected":false},"author":36,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[1590],"tags":[2679,2682,2683,2684],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":4}},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/posts\/131698"}],"collection":[{"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/users\/36"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/comments?post=131698"}],"version-history":[{"count":5,"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/posts\/131698\/revisions"}],"predecessor-version":[{"id":131703,"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/posts\/131698\/revisions\/131703"}],"wp:attachment":[{"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/media?parent=131698"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/categories?post=131698"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/biocienciatecnologia\/wp-json\/wp\/v2\/tags?post=131698"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}