Name: microbes driving iron and manganese cycles
Uploaded: 2026-03-12T13:57:36.000Z
Duration: 1 min 24 s
Channel: JoVE

Mikroben treiben den Kreislauf von Eisen und Mangan an, indem sie diese Elemente zwischen ihrer oxidierten und reduzierten Form verschieben.In neutralen, sauerstoffreichen Lebensräumen dominiert Eiseneisen in unlöslicher, ausgefällter Form.Einige Bakterien produzieren kleine Moleküle, sogenannte Siderophore, die an Eiseneisen binden und löslich machen.Die Zellen nehmen dann dieses lösliche Eisen auf und reduzieren es in die eisenhaltige Form für den metabolischen Gebrauch.An der oxisch-anoxischen Grenzfläche, wo der Sauerstoffgehalt niedrig ist, nutzen magnetotaktische Bakterien wie Magnetospirillum Eisen, um Magnetitkristalle zu bilden, die sich mit dem Erdmagnetfeld ausrichten, um anoxische Schichten zu erreichen.In derselben Zone oxidieren filamentöse Bakterien wie Leptothrix eisenhaltiges Eisen und bilden mit Eisenoxiden beschichtete Hüllen.Sie oxidieren außerdem Mangan(II) zu unlöslichem Mangandioxid, das in tiefere anoxische Schichten absinken kann, wo metallreduzierende Bakterien wie Geobacter es wieder in Mangan (II) umwandeln.In anoxischen Zonen führen Bakterien wie Shewanella eine dissimilatorische Eisenreduktion durch, wobei Eiseneisen der terminale Elektronenakzeptor ist.

microbes and other elemental cycles

Microbes and Other Elemental Cycles

Mikrobielle Aktivit&#xE4;t spielt eine zentrale Rolle in den biogeochemischen Kreisl&#xE4;ufen von Eisen und Mangan, insbesondere an den f&#xFC;r geschichtete aquatische Umgebungen charakteristischen Redoxgradienten. Diese Kreisl&#xE4;ufe werden durch mikrobielle Umwandlungen zwischen oxidierten und reduzierten Formen der Metalle angetrieben, wodurch Organismen sie f&#xFC;r metabolische Energie und strukturelle Zwecke nutzen k&#xF6;nnen.
Eisenkreislauf entlang von Redoxgradienten
In neutralen, sauerstoffreichen Oberfl&#xE4;chengew&#xE4;ssern liegt Eisen &#xFC;berwiegend in seiner oxidierten, unl&#xF6;slichen dreiwertigen [Fe(III)] Form vor. Um auf diesen essenziellen N&#xE4;hrstoff zugreifen zu k&#xF6;nnen, synthetisieren und sezernieren bestimmte Bakterien Siderophore &#x2013; niedermolekulare organische Verbindungen mit hoher Affinit&#xE4;t zu dreiwertigem Eisen. Diese Molek&#xFC;le binden dreiwertiges Eisen, machen es l&#xF6;slich und f&#xFC;r die Aufnahme verf&#xFC;gbar. Nach der Aufnahme wird dreiwertiges Eisen enzymatisch zur zweiwertigen [Fe(II)] Form reduziert, die bioverf&#xFC;gbarer ist und verschiedene zellul&#xE4;re Funktionen unterst&#xFC;tzt.
An der oxisch-anoxischen Grenzschicht, in der die Redoxbedingungen schwanken, oxidieren Bakterien wie Leptothrix l&#xF6;sliches zweiwertiges Eisen zu dreiwertigem Eisen und bilden dabei extrazellul&#xE4;re Eisenoxidh&#xFC;llen. Diese H&#xFC;llen erf&#xFC;llen einen doppelten Zweck: Sie verhindern die Zellinkrustation und k&#xF6;nnen strukturelle Unterst&#xFC;tzung bieten. Magnetotaktische Bakterien, die sich ebenfalls in dieser Zone befinden, nehmen Eisen auf und biomineralisieren Magnetitkristalle (Fe&#x2083;O&#x2084;). Diese Kristalle fungieren als intrazellul&#xE4;re Kompasse, die sich am Erdmagnetfeld ausrichten und die Zellen in sauerstoffarme Umgebungen lenken, die f&#xFC;r ihren Stoffwechsel optimal sind.
Acidophile Bakterien wie Acidithiobacillus f&#xF6;rdern den Eisenkreislauf in sauren, sauerstoffreichen Umgebungen. Diese Organismen gedeihen bei niedrigem pH-Wert und tragen zum Eisenumsatz bei, indem sie Fe&#xB2;&#x207A; (zweiwertiges Eisen) zu Fe&#xB3;&#x207A; (dreiwertigem Eisen) oxidieren. Dieser Oxidationsprozess ist in Umgebungen wie der sauren Grubenentw&#xE4;sserung von entscheidender Bedeutung.
Mangankreislauf in mikrobiellen Nischen
Leptothrix-Arten tragen auch zum Mangankreislauf bei, indem sie l&#xF6;sliche zweiwertige Manganionen [Mn(II)] zu unl&#xF6;slichem Mangandioxid [MnO&#x2082;]oxidieren, das in die darunter liegenden anoxischen Sedimente absinkt. In diesen Schichten reduzieren metallreduzierende Bakterien wie Geobacter das Mangandioxid enzymatisch wieder zu Mn(II) und schlie&#xDF;en so den Kreislauf. Ebenso nutzen phototrophe Bakterien unter anoxischen Bedingungen Fe(II) als Elektronendonator in der anoxygenen Photosynthese, w&#xE4;hrend fakultativ anaerobe Bakterien wie Shewanella dreiwertiges Eisen &#xFC;ber dissimilatorische Stoffwechselwege reduzieren, um Energie zu gewinnen.
Diese mikrobiellen Prozesse erhalten gemeinsam die Eisen- und Manganhom&#xF6;ostase in aquatischen &#xD6;kosystemen aufrecht und regulieren deren Verf&#xFC;gbarkeit und Verteilung an Redoxgrenzschichten.

Microbial activity plays a pivotal role in the biogeochemical cycling of iron and manganese, especially at the redox gradients characteristic of ...

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Education

Lehre

JoVE Core

Microbiology

Mikrobiologie

Unit

Einheit

Microbial Ecology

Mikrobielle Ökologie

KEY TERMS AND CONCEPTS

ZENTRALE BEGRIFFE UND KONZEPTE

microbes driving iron and manganese cycles

Microbes drive iron and manganese cycling in aquatic environments by changing these metals between reduced and oxidized forms. These reactions are especially important along redox gradients, where oxygen levels shift across stratified water layers. The microbes use these metals for energy, growth, and structural needs.

In oxygen-rich surface waters, iron is usually present as insoluble ferric iron, Fe(III). Some bacteria release siderophores, which are small organic molecules that bind ferric iron and make it soluble for uptake. After the iron enters the cell, enzymes reduce it to ferrous iron, Fe(II), which is easier for the cell to use.

At the oxic-anoxic interface, bacteria such as Leptothrix oxidize soluble Fe(II) back to Fe(III). This creates extracellular iron oxide sheaths around the cells. The sheaths help keep the cells from becoming encrusted and may also provide support. Magnetotactic bacteria live in this zone too. They build magnetite, Fe3O4, crystals inside the cell. These crystals act like tiny compasses and align with Earth’s magnetic field, helping the bacteria move toward low-oxygen conditions.

Acidophilic bacteria such as Acidithiobacillus also take part in iron cycling. They live in acidic, oxygen-rich environments and oxidize Fe(II) to Fe(III). This activity is important in places such as acid mine drainage systems. In manganese cycling, Leptothrix species oxidize soluble Mn(II) to insoluble manganese dioxide, MnO2. The MnO2 then sinks into anoxic sediments below.

In those sediments, metal-reducing bacteria such as Geobacter reduce manganese dioxide back to Mn(II). That closes the manganese cycle. Other microbes also use iron in special ways. Phototrophic bacteria under anoxic conditions use Fe(II) as an electron donor during anoxygenic photosynthesis. Facultative anaerobes such as Shewanella reduce ferric iron through dissimilatory pathways to gain energy. Together, these microbial processes control where iron and manganese are found in aquatic ecosystems and help maintain their cycling across redox interfaces.

Microbes Driving Iron and Manganese Cycles

microbes-driving-iron-and-manganese-cycles

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key terms and concepts

Learn how microbes move iron and manganese through aquatic environments, from siderophores and magnetite to metal reduction in redox zones.

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microbiology

Microbes Driving Iron and Manganese Cycles

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