{"id":143621,"date":"2013-12-26T16:08:28","date_gmt":"2013-12-26T15:08:28","guid":{"rendered":"http:\/\/www.madrimasd.org\/blogs\/universo\/?p=143621"},"modified":"2013-12-26T16:08:28","modified_gmt":"2013-12-26T15:08:28","slug":"los-microorganismos-del-suelo-y-su-creciente-resistencia-a-antibioticos-y-herbicidas","status":"publish","type":"post","link":"https:\/\/www.madrimasd.org\/blogs\/universo\/2013\/12\/26\/143621","title":{"rendered":"Los Microorganismos del Suelo y su Creciente Resistencia a Antibi\u00f3ticos y Herbicidas"},"content":{"rendered":"

Conforme los suelos son expuestos a herbicidas y antibi\u00f3ticos, sus microorganismos se tornan paulatinamente m\u00e1s resistentes a estos microbicidas<\/strong><\/span>. M\u00e1s aun, las parcelas de cultivo o pastos que han sufrido previamente tratamientos con estos \u00faltimos, degradan antes los nuevos productos de la misma \u00edndole que las \u201ccontrol\u201d previamente no expuestas. Si nos centramos en los antibi\u00f3ticos, que entran en el pack,<\/strong> <\/span>con los que se trata a los animales en la ganader\u00eda industrial<\/strong><\/span>, los mecanismos de resistencia pueden ser de diversa naturaleza<\/strong><\/span>. El genoma de algunos microorganismos mutan de tal forma que consiguen expulsar el agente toxico al exterior<\/strong><\/span>. En otras ocasiones su metabolismo lo modifica para que no les resulte t\u00f3xico<\/strong><\/span>. La noticia de hoy nos informa que se ha detectado un nuevo mecanismo. Al parecer ciertos actinomicetos<\/strong><\/span>, como Microbacterium<\/em><\/strong><\/span> (detectado tanto en el suelo<\/strong> <\/span>como en las plantas depuradoras de aguas residuales<\/strong><\/span>) logran romper la mol\u00e9cula de los antibi\u00f3ticos utilizando parte de sus fragmentos como fuente para su alimentaci\u00f3n en formas de carbono y nitr\u00f3geno<\/strong> <\/span>(dicho de otro modo que entran a engrosar los nutrimentos de su dieta). \u00a0Los investigadores responsables del estudio, cuya nota de prensa apareci\u00f3 en Sciencedaily<\/span><\/strong>, aplicaron varios<\/strong> antibi\u00f3ticos de uso veterinario en parcelas v\u00edrgenes frente a otras que hab\u00edan recibido previamente este tipo de t\u00f3xicos<\/strong><\/span>. La raz\u00f3n estriba en que<\/strong><\/span>, en muchas regiones, resulta altamente frecuente que los excrementos del ganado tratado se apliquen como fertilizantes org\u00e1nicos, al menos una vez al a\u00f1o (\u201ctoxic organic farmings?\u201d or \u201csmart microbial communities?<\/em><\/strong>).<\/span> Y efectivamente constataron que, tras once a\u00f1os, las parcelas que hab\u00edan recibido este abono t\u00f3xico con anterioridad lo \u201cmetabolizaban\u201d, como en el caso de los herbicidas, logrando alcanzar cepas microbianas de resistencia a los nuevos antibi\u00f3ticos mucho antes que los suelos que no hab\u00edan sido expuestos con anterioridad<\/strong><\/span>. Una de las conclusiones de estos investigadores, a ser corroborada, \u00a0estriba en que <\/span><\/span>las<\/span> bacterias del suelo podr\u00edan intercambiar genes<\/span><\/strong> (el t\u00edpico flujo horizontal que aparece en los procariotas) con vistas a romper las mol\u00e9culas de los antibi\u00f3ticos, m\u00e1s o menos simult\u00e1neamente<\/strong><\/span>.<\/p>\n

De todo ello (ya en parte conocido por investigaciones previas que os hemos mostrado en post precedentes), podemos concluir que (i)<\/strong> <\/span>la aplicaci\u00f3n continuada de herbicidas y antibi\u00f3ticos, genera que las comunidades microbianas del suelo se encuentren m\u00e1s preparadas para metabolizar otros nuevos, generando una retroalimentaci\u00f3n positiva que va en contra de las expectativas del agricultor y la vida media de estos productos en \u00e9l marcado; (ii)<\/strong><\/span> que como en el caso de los organismos humanos, aplicar (ingerir) tales sustancias continuadamente da\u00f1a la salud del receptor (les hace insensibles al tratamiento); (iii)<\/strong><\/span> la detecci\u00f3n de Microbacterium<\/em> en las depuradoras de aguas residuales sugiere que los mecanismos aplicados en las mismas pueden verse afectados a la hora de degradar los compuestos org\u00e1nicos t\u00f3xicos, o crear bacterias resistentes a los mismos (ya sea para bien o para mal de los intereses humanos) y (iv)<\/strong> que<\/span> los sistemas utilizados por la ganader\u00eda industrial son tanto insustentables como da\u00f1inos para la salud ciudadana<\/strong><\/span>.<\/p>\n

\"ganaderia-industrial-resistencia-a-antibioticos\"<\/p>\n

Ganader\u00eda Industrial: generando resistencia a los antibi\u00f3ticos en las comunidades microbianas del suelo. Fuente: Science Now<\/a><\/p>\n

Juan Jos\u00e9 Ib\u00e1\u00f1ez<\/strong><\/span><\/h3>\n

<\/span><\/h3>\n

Antibiotic-Eating Bug Unearthed in Soil: Newly Discovered Bacterium Degrades an Antibiotic Both to Protect Itself and Get Nutrition<\/a><\/strong><\/h3>\n

\u00a0<\/strong>Sciencedaily Dec. 7, 2012<\/em><\/strong> <\/span>\u2014 It’s well known how bacteria exposed to antibiotics for long periods will find ways to resist the drugs — by<\/strong> quickly pumping them out of their cells, for instance, or <\/strong>modifying the compounds so they’re no longer toxic.<\/p>\n

\u00a0Now new research has uncovered another possible mechanism of antibiotic \u00abresistance\u00bb in soil.<\/strong> In a paper published on Dec. 6 in the Journal of Environmental Quality<\/em>, a group of Canadian and French scientists report on a soil bacterium that breaks down the common veterinary antibiotic, sulfamethazine, and uses it for growth<\/strong>.<\/p>\n

Certain soil bacteria are already known to live off, or \u00abeat,\u00bb agricultural pesticides and herbicides<\/strong>, says the study’s leader, Ed Topp, a soil microbiologist with Agriculture and Agri-Food Canada in London, Ontario. In fact, the microbes’ presence in farm fields can cause these agrichemicals to fail<\/strong>.<\/p>\n

But to Topp’s knowledge, this is the first report of a soil microorganism that degrades an antibiotic both to protect itself and get nutrition<\/strong>.<\/p>\n

\u00abI think it’s kind of a game changer in terms of how we think about our environment and antibiotic resistance<\/strong>,\u00bb he says.<\/p>\n

Concerns about widespread antibiotic resistance are<\/strong> what led Topp and his collaborators to set up an experiment 14 years ago, in which they dosed soils annually with environmentally relevant concentrations of three veterinary antibiotics: sulfamethazine, tylosin, and chlortetracycline. Commonly fed to pigs and other livestock, antibiotics are thought to keep animals healthier<\/strong>. But they’re also excreted in manure, which is then spread once a year as fertilizer in countless North American farm fields<\/strong>.<\/p>\n

The researchers first wanted to know whether these yearly applications were promoting higher levels of antibiotic resistance in soil bacteria. But a few years ago, they also decided to compare the persistence of the drugs in soil plots that had been repeatedly dosed, versus fresh soils<\/strong> where antibiotics were never applied.<\/p>\n

They did this experiment, Topp explains, because of previous work indicating that pesticides often break down more quickly in soils with a long history of exposure<\/strong>, indicating that pesticide-degrading microbes have been selected for over time.<\/p>\n

Still, it came as a surprise when they saw antibiotics also degrading much faster in long-term, treated plots than in fresh, control soils<\/strong>, he says. In particular, sulfamethazine<\/strong> — a member of the antibiotic class called sulfonamides<\/strong> — disappeared up to five times faster.<\/p>\n

The researchers subsequently cultured from the treated plots a new strain of Microbacterium<\/em><\/strong>, an actinomycete that uses sulfamethazine as a nitrogen and carbon source<\/strong>. Extremely common in soil, actinomycete bacteria are known to degrade a wide range of organic compounds<\/strong>. And now at least two other sulfanomide-degrading Microbacterium <\/em>strains<\/strong> have been reported, Topp says: one from soil and another from a sewage treatment plant<\/strong>.<\/p>\n

Taken together, the findings suggest that the capability to break down sulfanomides could be widespread<\/strong>. And if it’s indeed true that \u00abthe microbiology in the environment is learning to break these drugs down more rapidly when exposed to them<\/strong>, this would effectively reduce the amount of time that the environment is exposed to these drugs and therefore possibly attenuate the impacts,\u00bb Topp says.<\/p>\n

Not that negative impacts aren’t still occurring, he cautions. In particular, long-term exposure to antibiotics puts significant pressure on soil bacteria to evolve resistance, which<\/strong> they typically do by giving and receiving genes that let them detoxify drugs, or keep the compounds out of their cells<\/strong>.<\/p>\n

What the new research suggests, though, is that soil bacteria could be swapping genes for breaking down antibiotics at the same time<\/strong>.<\/p>\n

\u00abMy guess is that’s probably what’s happening, but it remains to be determined,\u00bb Topp says. \u00abIt’s actually extremely fascinating.\u00bb<\/p>\n

The work was funded by Agriculture and Agri-Food Canada.<\/p>\n

Story Source<\/span>: <\/strong>The above story is reprinted from materials<\/a> provided by American Society of Agronomy<\/strong><\/a>. Note: Materials may be edited for content and length. For further information, please contact the source cited above.<\/em><\/p>\n

Journal Reference<\/strong><\/span>: Edward Topp, Ralph Chapman, Marion Devers-Lamrani, Alain Hartmann, Romain Marti, Fabrice Martin-Laurent, Lyne Sabourin, Andrew Scott, Mark Sumarah. Accelerated Biodegradation of Veterinary Antibiotics in Agricultural Soil following Long-Term Exposure, and Isolation of a Sulfamethazine-degrading sp.<\/strong>. Journal of Environment Quality<\/em>, 2012; DOI: 10.2134\/jeq2012.0162<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Conforme los suelos son expuestos a herbicidas y antibi\u00f3ticos, sus microorganismos se tornan paulatinamente m\u00e1s resistentes a estos microbicidas. M\u00e1s aun, las parcelas de cultivo o pastos que han sufrido previamente tratamientos con estos \u00faltimos, degradan antes los nuevos productos de la misma \u00edndole que las \u201ccontrol\u201d previamente no expuestas. Si nos centramos en los antibi\u00f3ticos, que entran en el pack, con los que se trata a los animales en la ganader\u00eda industrial, los mecanismos de resistencia pueden ser de diversa naturaleza. El genoma de algunos microorganismos mutan de tal forma que consiguen expulsar el agente toxico al exterior. En\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":[596,594,592,606],"tags":[46655,47422,46731,46657],"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\/143621"}],"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=143621"}],"version-history":[{"count":8,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/143621\/revisions"}],"predecessor-version":[{"id":144969,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/143621\/revisions\/144969"}],"wp:attachment":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/media?parent=143621"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/categories?post=143621"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/tags?post=143621"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}