Name: magnetotactic and dna-resistant bacteria
Uploaded: 2025-07-28T10:50:19.000Z
Duration: 1 min 18 s
Channel: JoVE

Las bacterias de dominio contienen algunas especies con propiedades extraordinarias, en particular las bacterias magnéticas y resistentes a la radiación.Las bacterias magnéticas, como Magnetospirillum magnetotacticum y Desulfovibrio magneticus, se encuentran típicamente cerca de la interfaz óxico-anóxica de los lagos estratificados.Estas especies bacterianas poseen magnetosomas. Un magnetosoma típicamente consiste en cadenas de partículas hechas de magnetita, en las especies aeróbicas, o greigita, en las especies anaeróbicas.Estas bacterias exhiben magnetotaxis. Sus magnetosomas se alinean con el campo geomagnético de la Tierra tanto en el hemisferio norte como en el sur, guiándolos a las zonas de transición óxico-anóxica.La resistencia a la radiación es una propiedad notable exhibida por los miembros del orden Deinococcales.La especie Deinococcus radiodurans puede sobrevivir a dosis de 15.000 grises de radiación ionizante.La disposición toroidal única de su ADN dentro de la célula y una estructura de pared celular multicapa juegan un papel clave en la resistencia a la radiación.

bacterias de ramificación profunda

Other Unique Bacteria

Las bacterias magn&#233;ticas presentan un movimiento dirigido denominado magnetotaxis, impulsado por estructuras llamadas magnetosomas. Estos magnetosomas est&#225;n compuestos por cadenas de part&#237;culas magn&#233;ticas formadas por magnetita (Fe_3O_4) o greigita (Fe_3S_4), organizadas en una conformaci&#243;n lineal mediante un armaz&#243;n proteico situado en invaginaciones de la membrana celular. Las bacterias se alinean a lo largo de las l&#237;neas del campo magn&#233;tico norte-sur, de forma similar a la aguja de una br&#250;jula. Generalmente, son microaer&#243;filas o anaerobias y se encuentran com&#250;nmente cerca de la interfaz &#243;xica-an&#243;xica en sedimentos o lagos estratificados. Las especies aer&#243;bicas suelen contener magnetita en sus magnetosomas, mientras que las anaerobias contienen greigita.
El papel ecol&#243;gico de los magnetosomas bacterianos sigue sin estar claro, aunque podr&#237;an conferir una ventaja selectiva al mantener a las bacterias en zonas con bajo contenido de ox&#237;geno. Los niveles de ox&#237;geno suelen disminuir con la profundidad en los sedimentos y en los lagos estratificados. Dado que el campo magn&#233;tico terrestre posee un componente vertical intenso en ambos hemisferios, las bacterias magnetot&#225;cticas se alinean con estas l&#237;neas para nadar hacia abajo, alej&#225;ndose del ox&#237;geno. El magnetosoma act&#250;a como una br&#250;jula, mientras que el movimiento flagelar est&#225; controlado por una respuesta quimiot&#225;ctica al ox&#237;geno.
Las bacterias magn&#233;ticas presentan diferentes polaridades magn&#233;ticas seg&#250;n la orientaci&#243;n de sus magnetosomas. En el hemisferio norte, las bacterias que buscan el norte se desplazan hacia abajo, mientras que en el hemisferio sur, las bacterias que buscan el sur realizan un movimiento similar.
La mayor&#237;a de las bacterias magn&#233;ticas pertenecen al grupo de las Alphaproteobacteria, aunque tambi&#233;n se han identificado especies en los grupos Gammaproteobacteria, Deltaproteobacteria y Nitrospira. Una especie bien caracterizada, Magnetospirillum magnetotacticum, es un microaer&#243;filo quimioorgan&#243;trofo que tambi&#233;n puede crecer en condiciones anaerobias mediante la reducci&#243;n de nitrato (NO_3 ^-) o de &#243;xido nitroso (N_2O). Otra especie, Desulfovibrio magneticus, es un anaerobio estricto reductor de sulfato. Tambi&#233;n se han observado magnetosomas en bacterias oxidadoras de azufre y en bacterias p&#250;rpuras no sulfurosas.
Adem&#225;s, existen bacterias magnetot&#225;cticas multicelulares. Estas Deltaproteobacteria forman agregados de 10 a 20 c&#233;lulas dispuestas en una esfera hueca. Aunque son anaerobias estrictas, sus v&#237;as metab&#243;licas exactas a&#250;n no se conocen.
Deinococcus radiodurans, miembro del orden Deinococcales, presenta una elevada resistencia a la radiaci&#243;n y a la desecaci&#243;n, pudiendo sobrevivir a dosis de hasta 15.000 Gy. Suele tener una coloraci&#243;n roja o rosada debido a la presencia de carotenoides y se a&#237;sla de suelos, carne, polvo y aire. Aunque es resistente a la mayor&#237;a de los mut&#225;genos, es vulnerable a las deleciones en el ADN.
Su sistema de reparaci&#243;n del ADN incluye m&#250;ltiples enzimas, lo que permite una recuperaci&#243;n eficiente tras el da&#241;o por radiaci&#243;n. D. radiodurans organiza su ADN en una estructura toroidal, lo que facilita la recombinaci&#243;n hom&#243;loga, permitiendo reensamblar cromosomas fragmentados. Esta extraordinaria capacidad de reparaci&#243;n permite a la c&#233;lula reanudar su crecimiento y divisi&#243;n incluso despu&#233;s de un da&#241;o extremo en el ADN.

Bacterias de ramificación profunda

Las bacterias magn&#233;ticas presentan un movimiento dirigido denominado magnetotaxis, impulsado por estructuras llamadas magnetosomas. Estos ...

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magnetotactic and dna-resistant bacteria

Magnetotactic bacteria move using Earth’s magnetic field, and some bacteria are known for extreme DNA repair. These unusual microbes show two very different survival strategies. One uses magnetic particles to guide movement. The other can recover after severe radiation damage.

Magnetotaxis is the directed movement seen in magnetic bacteria. It depends on magnetosomes, which are chains of magnetic particles made of magnetite (Fe₃O₄) or greigite (Fe₃S₄). A protein scaffold keeps these particles lined up inside membrane folds, and the cells then align with north–south magnetic field lines like a compass needle.

These bacteria are usually microaerophilic or anaerobic, so they live where oxygen is low. They are common near the oxic–anoxic interface in sediments and stratified lakes, where oxygen levels drop with depth. Aerobic species usually contain magnetite in their magnetosomes, while anaerobic species usually contain greigite. The magnetosome may help keep the cells in low-oxygen zones.

Earth’s magnetic field has a strong vertical component in both hemispheres. That helps magnetotactic bacteria swim downward, away from oxygen. The magnetosome acts like a compass, while flagellar movement is guided by a chemotactic response to oxygen. These bacteria also show different magnetic polarities. In the Northern Hemisphere, north-seeking bacteria move downward, and in the Southern Hemisphere, south-seeking bacteria do the same.

Most magnetic bacteria belong to the Alphaproteobacteria, but some are found in the Gammaproteobacteria, Deltaproteobacteria, and Nitrospira group. Magnetospirillum magnetotacticum is a chemoorganotrophic microaerophile that can also grow without oxygen by reducing nitrate (NO₃⁻) or nitrous oxide (N₂O). Desulfovibrio magneticus is a sulfate-reducing obligate anaerobe. Magnetosomes have also been seen in sulfur oxidizers and purple nonsulfur bacteria, and multicellular magnetotactic bacteria also exist.

These multicellular magnetotactic bacteria are Deltaproteobacteria that form groups of 10 to 20 cells in a hollow sphere. They are obligate anaerobes, but their exact metabolism is still unknown. Another unusual bacterium, Deinococcus radiodurans, is famous for surviving radiation and drying out. It can survive doses of 15,000 Gy and is often red or pink because of carotenoids. It is found in soil, meat, dust, and air.

D. radiodurans is resistant to most mutagens, but it is vulnerable to DNA deletions. Its DNA repair system uses multiple enzymes to rebuild damaged DNA after radiation exposure. The cell also arranges its DNA in a toroidal, or ring-like, structure. This shape supports homologous recombination and helps fragmented chromosomes be put back together. As a result, the cell can resume growth and division after extreme DNA damage.

Magnetotactic and DNA-Resistant Bacteria

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other unique bacteria

Magnetotactic bacteria move using Earth’s magnetic field, and some bacteria are known for extreme DNA repair. These unusual microbes show two very different survival strategies. One uses magnetic particles to guide movement. The other can recover after severe radiation damage. Magnetotaxis is the directed movement seen in magnetic bacteria. It depends on magnetosomes, which are chains of magnetic particles made of magnetite (Fe₃O₄) or greigite (Fe₃S₄). A protein scaffold keeps these particles...

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key terms and concepts

Explore magnetotactic bacteria, magnetosomes, and how Deinococcus radiodurans repairs DNA after extreme radiation damage in this high school biology page.

Magnetotactic and DNA-Resistant Bacteria | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Magnetotactic and DNA-Resistant Bacteria

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