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

I batteri contengono alcune specie con proprietà straordinarie, in particolare i batteri magnetici e resistenti alle radiazioni.I batteri magnetici, come il Magnetospirillum magnetotacticum e il Desulfovibrio magneticus, si trovano tipicamente vicino all'interfaccia ossico-anossica dei laghi stratificati.Queste specie batteriche possiedono magnetosomi. Un magnetosoma è tipicamente costituito da catene di particelle costituite da magnetite, nelle specie aerobiche, o greigite, nelle specie anaerobiche.Questi batteri mostrano magnetotassi. I loro magnetosomi si allineano con il campo geomagnetico terrestre sia nell'emisfero settentrionale che in quello meridionale, guidandoli verso le zone di transizione ossico-anossica.La resistenza alle radiazioni è una proprietà notevole mostrata dai membri dell'ordine dei Deinococcales.La specie Deinococcus radiodurans può sopravvivere a dosi di 15.000 grigi di radiazioni ionizzanti.L'esclusiva disposizione toroidale del suo DNA all'interno della cellula e una struttura multistrato della parete cellulare svolgono un ruolo chiave nella resistenza alle radiazioni.

batteri con ramificazioni profonde

Other Unique Bacteria

I batteri magnetotattici presentano un movimento direzionale detto magnetotassi, guidato da strutture denominate magnetosomi. Questi magnetosomi sono costituiti da catene di particelle magnetiche di magnetite (Fe_3O_4) o greigite (Fe_3S_4), organizzate in conformazione lineare da uno scaffold proteico all&#8217;interno di invaginazioni della membrana cellulare. I batteri si allineano lungo le linee del campo magnetico nord&#8211;sud, analogamente a un ago magnetico. Sono tipicamente microaerofili o anaerobi e si trovano comunemente vicino all&#8217;interfaccia ossico&#8211;anossica nei sedimenti o nei laghi stratificati. Le specie aerobie contengono generalmente magnetite nei loro magnetosomi, mentre quelle anaerobie contengono greigite.
Il ruolo ecologico dei magnetosomi nei batteri rimane poco chiaro, ma potrebbe conferire un vantaggio selettivo mantenendo i batteri in zone a basso contenuto di ossigeno. I livelli di ossigeno tendono a diminuire con la profondit&#224; nei sedimenti e nei laghi stratificati. Poich&#233; il campo magnetico terrestre ha una componente verticale marcata in entrambi gli emisferi, i batteri magnetotattici si allineano con queste linee per nuotare verso il basso, lontano dall&#8217;ossigeno. Il magnetosoma funziona come una bussola, mentre il movimento flagellare &#232; controllato da una risposta chemiotattica all&#8217;ossigeno.
I batteri magnetotattici mostrano polarit&#224; magnetiche differenti in base all&#8217;orientamento dei loro magnetosomi. Nell&#8217;emisfero settentrionale, i batteri diretti verso nord si muovono verso il basso, mentre nell&#8217;emisfero meridionale lo fanno quelli diretti verso sud.
La maggior parte dei batteri magnetotattici appartiene agli Alphaproteobacteria, ma sono state identificate specie anche tra i Gammaproteobacteria, Deltaproteobacteria e nel gruppo Nitrospira. Una specie ben caratterizzata, Magnetospirillum magnetotacticum, &#232; un microaerofilo chemoorganotrofo che pu&#242; crescere anche in condizioni anaerobiche riducendo nitrato (NO_3^-) o protossido di azoto (N_2O). Un&#8217;altra specie, Desulfovibrio magneticus, &#232; un anaerobio obbligato riduttore di solfato. I magnetosomi sono stati osservati anche in batteri ossidanti lo zolfo e in batteri purpurei non sulfurei.
Esistono inoltre batteri magnetotattici multicellulari. Questi Deltaproteobacteria formano aggregati di 10&#8211;20 cellule disposte in una sfera cava. Sebbene siano anaerobi obbligati, i loro percorsi metabolici esatti restano sconosciuti.
Deinococcus radiodurans, appartenente all&#8217;ordine Deinococcales, &#232; altamente resistente alle radiazioni e alla disidratazione, sopravvivendo a dosi di 15.000 Gy. Ha colore rosso o rosa dovuto alla presenza di carotenoidi ed &#232; isolato da suolo, carne, polvere e aria. Sebbene resistente alla maggior parte dei mutageni, &#232; vulnerabile alle delezioni del DNA.
Il suo sistema di riparazione del DNA &#232; unico e comprende numerosi enzimi che consentono un recupero efficiente dai danni da radiazione. D. radiodurans organizza il proprio DNA in una struttura toroidale, che facilita la ricombinazione omologa, permettendo il riassemblaggio dei cromosomi frammentati. Questa eccezionale capacit&#224; di riparazione consente alla cellula di riprendere crescita e divisione anche dopo gravi danni al DNA.

Batteri con Ramificazioni Profonde

I batteri magnetotattici presentano un movimento direzionale detto magnetotassi, guidato da strutture denominate magnetosomi. Questi magnetosomi sono ...

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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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diversity of archaea ii

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Microsporidia Spores and Host Infection

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fungal phylum basidiomycota

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diversity of protists i

Excavata Protists and Their Adaptations

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diversity of protists iii

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diversity of protists iv

Amoebozoa: Movement and Life Cycles

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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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