{"id":131475,"date":"2010-01-18T10:18:00","date_gmt":"2010-01-18T10:18:00","guid":{"rendered":"http:\/\/weblogs.madrimasd.org\/\/universo\/archive\/2010\/01\/18\/131475.aspx"},"modified":"2010-01-22T04:01:16","modified_gmt":"2010-01-22T03:01:16","slug":"la-revolucion-neolitica-de-los-organismos-del-suelo-sobre-el-ciclo-del-nitrogeno-monocultivos-hormigas-y-bacterias","status":"publish","type":"post","link":"https:\/\/www.madrimasd.org\/blogs\/universo\/2010\/01\/18\/131475","title":{"rendered":"La Revoluci\u00f3n Neol\u00edtica de los Organismos del Suelo: Sobre el Ciclo del Nitr\u00f3geno, Monocultivos, Hormigas y Bacterias"},"content":{"rendered":"


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Por no inventar, ni los monocultivos. El ser humano, con su tecnolog\u00eda, suele redescubrir mecanismos ya desarrollados por otros organismos vivos. Sin embargo, mientras los segundos son sustentables, los nuestros no. Ni siquiera plagiamos bien, como los malos estudiantes. Nuestros cultivos requieren necesariamente (\u00bf?) fertilizaci\u00f3n, mientras que los de las hormigas y termitas no. Homo sapiens sapiens<\/em> dedicados a edaf\u00f3logos descubrieron hace unas d\u00e9cadas la fijaci\u00f3n biol\u00f3gica del nitr\u00f3geno por los microorganismos (ya sean especies que viven libremente, o asociadas a los sistemas radicales de ciertas plantas vasculares). Sin embargo, las cantidades producidas no eran suficientes con vistas a cubrir sus demandas, derivadas de un desorbitado crecimiento demogr\u00e1fico y excesivo productivismo. En consecuencia, desarrollamos los fertilizantes nitrogenados. Su uso y abuso ha convertido el medio ambiente en una cloaca, alterando seriamente el ciclo del nitr\u00f3geno de la biosfera. Diversos expertos opinan que, este \u00faltimo, ha sido afectado m\u00e1s seriamente que el del propio carbono, aunque de momento no nos percatemos de todas las consecuencias. Los dos notas que comentaremos hoy, que dan cuenta de otros tantos art\u00edculos de investigaci\u00f3n, nos informan de que para otras especies: (i) los monocultivos si pueden ser sustentables durante decenas de millones de a\u00f1os; (ii) que su actividad no solo les basta para subsistir, sino que, regalan nitr\u00f3geno a la biosfera, ya que se acumulan evidencias de que los cultivos de hongos llevados a cabo por hormigas y termitas desprenden una enorme cantidad de este elemento en forma asimilable, esencial para el funcionamiento de los ecosistemas tropicales y subtropicales; (iii) al construir sus gigantescos nidos \u201clabran el suelo (bioturbaci\u00f3n) de un modo tambi\u00e9n sustentable, permitiendo el reciclado de nutrientes que, de otro modo, se perder\u00edan por los lixiviados pluviales de los sistemas ed\u00e1ficos muy pobres en los mismos\u00a0 <\/span>y (iv) que las ciudades con millones de individuos, no solo son sustentables, sino incluso beneficiosas para la salud de la biosfera. \u00bfHan falta m\u00e1s lecciones para ilustrar que andamos por mal camino? <\/span><\/p>\n

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Termitomicetos esparciendo esporas en <\/a><\/span><\/p>\n

las salidas de los termiteros. Fuente: Wikipedia<\/a><\/span><\/span><\/span><\/p>\n

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Ya s\u00e9, alegar\u00e9is que las grandes diferencias existentes entre estos bobos animales y la superdotada inteligencia humana invalidan tal paralelismo conceptual. Empero a las pruebas me remito. Hormigas y bacterias han sobrevivido durante decenas de millones de a\u00f1os, mientras nosotros vamos caminos de la extinci\u00f3n en unos 10.000 a\u00f1itos,<\/span><\/strong> de no cambiar dr\u00e1sticamente de rumbo.<\/span><\/p>\n

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Las dos noticias extra\u00eddas de Sciencedaily<\/span><\/strong> espaciadas en el plazo de muy pocos d\u00edas, dan cuanta de las actividades de hormigas y termitas<\/span><\/strong>, as\u00ed como de su potencial para que puedan edificarse los ecosistemas tropicales y subtropicales<\/span><\/strong> que tanto nos fascinan. \u00bfC\u00f3mo ser\u00edan estos \u00faltimos sin la existencia de estos organismos ed\u00e1ficos?<\/span><\/strong> Con toda seguridad, muy diferentes<\/span><\/strong>. Y aun as\u00ed, seguimos despreciando la imperiosa necesidad de abordar seriamente un inventario de los seres vivos que habitan en el suelo<\/span><\/strong>. \u00bfNo somos imb\u00e9ciles? Lo que s\u00ed ha demostrado el ser humano es que la idiotez e inteligencia pueden cohabitar sin mayores problemas. \u00bfAhora bien se puede sobrevivir as\u00ed? \u00a0<\/span>Probablemente tan solo durante un breve lapso de tiempo, si no utilizamos nuestro cerebro y la tecnolog\u00eda derivada de \u00e9l de una manera m\u00e1s eficiente. <\/span><\/p>\n

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Como se\u00f1ala la primera noticia<\/span><\/strong>, tan solo en el bosque amaz\u00f3nico las hormigas cuadruplican la biomasa de todos los dem\u00e1s animales juntos, sin alterar el equilibrio<\/span><\/strong> del ecosistema, sino gener\u00e1ndole imprescindibles beneficios<\/span><\/strong>.\u00a0 <\/span>\u00bfCu\u00e1nto ascender\u00eda tal cifra si se sumaran todos los organismos que viven en el suelo? <\/span><\/p>\n

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Cultivo de los hongos por las termitas sobre sustrato de madera. <\/a><\/span><\/p>\n

Fuente: Universidad de Davis <\/a><\/span><\/span><\/span><\/p>\n

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Tanto hormigas <\/span><\/strong>como termitas<\/span><\/strong>, adolecer\u00edan de un alimento de muy mala calidad, y posiblemente cultivos de escasa productividad, si no fuera porque introducen en el sustrato y\/o su propio cuerpo bacterias fijadoras de nitr\u00f3geno atmosf\u00e9rico<\/span><\/strong>. Dicho de otro modo, sin el auxilio de tales organismos simbi\u00f3nticos<\/span><\/strong> ellas mismas tampoco podr\u00edan sobrevivir. Obviamente hablamos de mutualismo<\/span><\/strong>, pero hay matices. Desde luego, de acuerdo a los estudios que abajo os muestro, la actividad de las bacterias fijadoras de nitr\u00f3geno no parece ser accidental. No se comportan como turistas accidentales<\/span><\/strong>, precisamente. <\/span><\/p>\n

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Las hormigas, requieren de tales bacterias a la hora de construir los huertos subterr\u00e1neos de hongos imprescindibles en su alimentaci\u00f3n<\/span><\/strong>. Cortan y trasladan restos de hojas a sus nidos. Estos servir\u00e1n, junto a sus propias heces, como sustrato para el cultivo de sus \u201cchampi\u00f1ones\u201d. Pero para que tal actividad tenga \u00e9xito, requieren una hasta ahora desconocida simbiosis con las ya mentadas bacterias fijadoras de nitr\u00f3geno<\/span><\/strong>. Su \u00e9xito evolutivo ha sido tan enorme, que se sospecha que tal \u201cagricultura\u201d proporciona la mayor fuente de nitr\u00f3geno del suelo en los ambientes tropicales<\/span><\/strong> (y en menor medida de otros), un factor otrora limitante para el desarrollo de la vegetaci\u00f3n<\/span><\/strong>. Como m\u00ednimo, tal agricultura a permanecido<\/span><\/strong> sin generar problemas (m\u00e1s bien todo lo contrario) desde hace 50 millones de a\u00f1os, alimentando sus ciudades subterr\u00e1neas compuestas por varios millones de individuos. \u00bfEsto no es sustentabilidad? <\/span>Y hablamos de monocultivos<\/span><\/strong>.<\/span><\/p>\n

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Termitero Gigante en Australia (<\/span>Litchfield nat.park<\/span>). <\/span><\/a><\/span><\/p>\n

Fuente: ravellpod.com<\/a><\/span><\/span><\/span><\/p>\n

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Pero lo mismo ocurre tambi\u00e9n con las termitas, tambi\u00e9n en los neotr\u00f3picos<\/span><\/strong>, desde hace al menos 30 millones de a\u00f1os. En \u00c1frica, parecen cohabitar unas 330 especies<\/span><\/strong> de estos animalitos, sin que se exterminen entre s\u00ed, hasta que solo quedara una. Por tanto, como en el caso de las hormigas, se convierten en uno (si no el que m\u00e1s) de los principales recicladotes de nutrientes y materia org\u00e1nica en los bosques tropicales h\u00famedos africanos<\/span><\/strong>. Al menos en el caso de las termitas, siembran esporas de<\/span><\/strong> los denominados \u201ctermitomicetos<\/a>\u201d. Pero no son ego\u00edstas, ya que al menos una vez al a\u00f1o, los cuerpos fruct\u00edferos de los estos hongos afloran por la boca de los termiteros, dispersando al ambiente sus esporas. Un hecho sorprendente deviene que, de alguna forma, su actividad selecciona tan solo un determinado genotipo del hongo cultivado, entre otros muchos existentes en la naturaleza, algunos de los cuales tambi\u00e9n est\u00e1n presentes en el sustrato inicial del cultivo<\/span><\/strong>. Por sorprendente que parezca, parece existir pues alg\u00fan tipo de selecci\u00f3n gen\u00e9tica de los cultivares<\/span><\/strong>. Y aqu\u00ed nosotros redescubriendo la \u201cdinamita\u201d. En mi opini\u00f3n se necesitan estudios m\u00e1s detallados que nos demuestren como realizan tales tareas, con vistas a aprender algo de la tan cacareada sustentabilidad. Dime de que presumes y te dir\u00e1 de qu\u00e9 careces. <\/span><\/p>\n

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Os dejo en este enlace una maravillosa descripci\u00f3n<\/a> que a tal respecto nos realiza Lynn Margulis, la \u201cmadre\u201d de la teor\u00eda simbiogen\u00e9tica de la evoluci\u00f3n<\/span><\/strong>. No os la perd\u00e1is. \u00a0<\/span>\u00a0<\/span>\u00a0\u00a0\u00a0<\/span>\u00a0<\/span><\/span><\/p>\n

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Juan Jos\u00e9 Ib\u00e1\u00f1ez<\/span><\/p>\n

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Ants Use Bacteria to Make Their Gardens G<\/span>row<\/a><\/span><\/strong><\/p>\n

ScienceDaily (Nov. 24, 2009)<\/span><\/strong> \u2014 Leaf-cutter ants, which cultivate fungus for food, have many remarkable qualities.<\/span><\/strong><\/span><\/p>\n

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Here’s a new one to add to the list: the ant farmers, like their human counterparts, depend on nitrogen-fixing bacteria to make their gardens grow<\/span><\/strong>. The finding, reported Nov. 20 in the journal Science<\/span><\/strong>, documents a previously unknown symbiosis<\/span> between ants and bacteria and provides insight into how <\/span>leaf-cutter ants have come to dominate the American tropics and subtropics<\/span><\/strong>. What’s more, the work, conducted by a team led by University of Wisconsin-Madison bacteriologist Cameron Currie, identifies what is likely the <\/span>primary source of terrestrial nitrogen in the tropics<\/span>, a setting where nutrients are otherwise scarce<\/span><\/strong>. \u00abNitrogen is a limiting resource<\/span><\/strong>,\u00bb says Garret Suen, a UW-Madison postdoctoral fellow and a co-author of the new study. <\/span>\u00abIf you don’t have it, you can’t survive.\u00bb<\/span><\/p>\n

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Indeed, the partnership between ant and microbe permits leaf-cutters to be amazingly successful<\/span><\/strong>. Their underground nests<\/span><\/strong>, some the size of small houses, can harbor millions of inhabitants<\/span><\/strong>. In the Amazon forest they comprise four times more biomass than do all land animals combined<\/span><\/strong>.<\/span><\/p>\n

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\u00abThis is the first indication of bacterial garden symbionts in the fungus-growing ant system,<\/span><\/strong>\u00bb says Currie, a UW-Madison professor of bacteriology. A critical finding in the new study, according to the <\/span>Wisconsin<\/span> scientist, is that the nitrogen, which is extracted from the air by the bacteria, ends up in the ants themselves and, ultimately, benefits the nitrogen-poor ecosystems where the ants thrive<\/span><\/strong>.<\/span><\/p>\n

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The fungus-growing ants<\/span><\/strong>, Currie notes, are technically herbivores<\/span><\/strong>. They make their living by carving up foliage and carrying it back to their nests in endless columns to provide the raw material for the fungus they grow as food.<\/span><\/strong> \u00abBut <\/span><\/strong>plant-feeding insects are known to be nitrogen limited<\/span><\/strong>,\u00bb explains Currie, \u00aband the plant biomass nitrogen is lower than what the insects need for survival<\/span><\/strong>.\u00bb<\/span><\/p>\n

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Enter the nitrogen-fixing bacteria<\/span><\/strong>, two species<\/span><\/strong> of which were isolated in laboratory and field colonies of the ants<\/span><\/strong>. But merely finding the bacteria, Suen emphasizes, wasn’t enough. <\/span>It was necessary to prove that the ants were actually utilizing the nutrient to <\/span>confirm a true mutualism<\/span>. \u00abThis is important because<\/span><\/strong> it could be that the bacteria are fixing nitrogen for themselves and not actually benefiting the ants,\u00bb says Suen. \u00abShowing that the nitrogen fixed by the bacteria is incorporated into the ants establishes that these bacteria aren’t just transient visitors.<\/span><\/strong>\u00ab. <\/span><\/p>\n

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One other type of insect, the termite, has been previously shown to utilize nitrogen-fixing bacteria. And other bacteria-ant symbioses have been documented<\/span><\/strong>.<\/span><\/p>\n

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However, the discovery of the nitrogen-fixing mutualism in ants has significant ecological implications given the dominance of ants in virtually all of the word’s terrestrial ecosystems. The new work suggests that an important source of nitrogen in the American tropics and subtropics is <\/span>derived through the partnership of ant and bacteria<\/span><\/strong>. Says Currie: \u00abIt is possible that this fixed nitrogen can have ecosystem scale impacts<\/span><\/strong>.\u00bb The partnership with bacteria, which Currie says could extend back to the origins of the gardening ants some 50 million years ago<\/span><\/strong>, confers a competitive edge that has permitted the leaf-cutters to prevail in their environments.<\/span><\/p>\n

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Says Suen: \u00abWithout nitrogen, there is no way these guys could achieve such large colony sizes. These ants are one of the most dominant insects in the Neotropics<\/span>.<\/span> The ability to have colonies with millions of ants is predicted to require a tremendous amount of nitrogen<\/span><\/strong>.\u00bb<\/span><\/p>\n

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The new study was funded in part by the U.S. Department of Energy through the <\/span>Great Lakes<\/span> <\/span>Bioenergy<\/span> <\/span>Research<\/span> <\/span>Center<\/span> and the National Science Foundation. In addition to Currie and Suen, the new study was co-authored by Adrian A Pinto-Tomas now of the University of Costa Rica; Mark A. Anderson, Fiona S. T. Chu and W. Wallace Cleland of UW-Madison; and David M. Stevenson and Paul J. Weimer of the U.S. Department of Agriculture’s Dairy Forage Research Center. (\u2026) Story Source<\/span><\/strong>: Adapted from materials provided by <\/span>University of Wisconsin-Madison<\/span><\/a><\/span>, via <\/span>EurekAlert!<\/span><\/a><\/span>, a service of AAAS. <\/span><\/p>\n

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Termites Create Sustainable Monoculture Fungus Farming<\/a><\/span><\/strong><\/p>\n

ScienceDaily (Nov. 22, 2009)<\/span><\/strong> \u2014 Food production of modern human societies is mostly based on large-scale monoculture crops, but it now appears that advanced insect societies have the same practice<\/span><\/strong>. Our societies<\/span><\/strong> took just ten thousand years of (mainly cultural<\/span><\/strong>) evolution to adopt this habit and we are far from convinced that it is sustainable<\/strong>. <\/span><\/span>Farming ants and termites had tens of millions of years to evolve their fungus farming systems and here monocultures are apparently evolutionary stable<\/span><\/strong>. In a study published in the journal Science<\/span><\/strong>, researchers from the Laboratory of Genetics of <\/span>Wageningen<\/span><\/span><\/strong> <\/span><\/strong>University<\/span><\/strong> and the Centre for Social Evolution at the <\/span>University<\/span> of <\/span>Copenhagen<\/span> take significant steps to resolve this puzzle.<\/span><\/p>\n

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The fungus-growing termites of the old-world tropics build<\/span><\/strong> impressive mounds consisting of thousands of workers and soldiers. These societies domesticated African Termitomyces mushrooms more than 30 million years<\/span><\/strong> ago and became obligatorily dependent on farming their own fungal food in their often gigantic nest mounds<\/span><\/strong>. The termite fungus-farming symbiosis<\/span> had a single African rain-forest origin and now comprises ca 330 species<\/span><\/strong>. It is of major <\/span>ecological importance for decomposition and mineral cycling<\/span><\/strong>. A colony-founding termite queen and king normally do not acquire their first garden until they have raised the first workers. <\/span>These helpers collect Termitomyces spores while foraging, together with the plant material that they defecate in the nest to establish a garden substrate. These spores are amply available because the fungus gardens produce large mushrooms once a year on top of the termite mounds<\/span><\/strong>.<\/span><\/p>\n

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However, this farming practice offers a paradox: Evolutionary theory predicts that symbioses with multiple lineages per colony should be unstable, because <\/span><\/strong>these genotypes can be expected to compete for making mushrooms rather than collaborate to serve the termite farmers. The new study shows that a very special mechanism is in place to prevent this from happening. <\/span>All colonies from which multiple fungal samples were genetically analyzed contained only a single fungal genotype in spite of gardens having been initiated from at least two and probably many more genetically different spores<\/span><\/strong>.<\/span><\/p>\n

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Duur Aanen, Koos Boomsma and their respective colleagues in Wageningen and <\/span>Copenhagen<\/span> show that genotypes that happen to be common in a garden, become even more common at the expense of rarer genotypes. <\/span>This happens not because common genotypes are better direct competitors, but because they have a higher chance of having an identical genotype as neighbor. Every time this happens, such genetically identical mycelia merge, which enhances the efficiency by which they produce asexual spores that the termites eat and deposit in new garden material of the colony. <\/span>This process of positive reinforcement makes every colony end up with a life-time commitment to a single fungal symbiont in spite of the population at large having many fungal genotypes. (\u2026) Story Source<\/span><\/strong>: Adapted from materials provided by <\/span>Wageningen University and Research Centre<\/span><\/a><\/span>, via <\/span>AlphaGalileo<\/span><\/a><\/span>.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Por no inventar, ni los monocultivos. El ser humano, con su tecnolog\u00eda, suele redescubrir mecanismos ya desarrollados por otros organismos vivos. Sin embargo, mientras los segundos son sustentables, los nuestros no. Ni siquiera plagiamos bien, como los malos estudiantes. Nuestros cultivos requieren necesariamente (\u00bf?) fertilizaci\u00f3n, mientras que los de las hormigas y termitas no. Homo sapiens sapiens dedicados a edaf\u00f3logos descubrieron hace unas d\u00e9cadas la fijaci\u00f3n biol\u00f3gica del nitr\u00f3geno por los microorganismos (ya sean especies que viven libremente, o asociadas a los sistemas radicales de ciertas plantas vasculares). Sin embargo, las cantidades producidas no eran suficientes con vistas a cubrir\u2026<\/p>\n","protected":false},"author":26,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[596,608,590,613,600],"tags":[],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":4}},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/131475"}],"collection":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/users\/26"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/comments?post=131475"}],"version-history":[{"count":7,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/131475\/revisions"}],"predecessor-version":[{"id":135070,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/131475\/revisions\/135070"}],"wp:attachment":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/media?parent=131475"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/categories?post=131475"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/tags?post=131475"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}