Name: bacterial flagella as tiny rotary motors
Uploaded: 2025-06-12T09:30:47.000Z
Duration: 1 min 18 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.c

Flagella and Motility in Bacteria

Flagellen sind dünne, fadenförmige Fortsätze, die sich von der Plasmamembran und der Zellwand erstrecken und Bakterien bei der Beweglichkeit unterstützen. Das Flagellum besteht aus drei Hauptteilen – dem Filament, dem Haken und dem Basalkörper. Das Filament, der sichtbare Teil des Flagellums, besteht aus Flagellin-Protein-Untereinheiten, die in spiralförmigen Ketten angeordnet sind. Er ist durch den Haken mit seinem Basalkörper verbunden. Der Basalkörper besteht aus einem zentralen Stäbchen, das durch eine Reihe von Proteinringen verläuft. Gramnegative Bakterien haben vier Basalkörperringe. Der L-Ring ist an der Lipopolysaccharidschicht verankert, der P-Ring ist in die Peptidoglykanschicht eingebettet und die MS- und C-Ringe sind an die Plasmamembran bzw. das Zytoplasma gebunden. Der Basalkörper des grampositiven Bakteriums enthält nur die MS- und C-Ringe. Der Basalkörper fungiert als Motor, der von der Protonenantriebskraft angetrieben wird, wodurch sich das Flagellum drehen und die Bakterien sich fortbewegen können. Neben der Beweglichkeit helfen Flagellen den Bakterien, sich an Oberflächen zu heften, und tragen bei einigen Bakterien zur Virulenz bei, indem sie die Infektion unterstützen.

flagellen und motilität bei bakterien

Flagellen sind spezialisierte, fadenartige Strukturen, die aus der Zellh&#252;lle von Bakterien hervorragen. Sie spielen eine entscheidende Rolle bei der Motilit&#228;t und Chemotaxis. Ihre strukturelle Organisation und Funktionalit&#228;t sind Zeichen von fortgeschrittener evolution&#228;rer Anpassung, die das &#220;berleben und die Adaption von Bakterien in unterschiedlichen Umgebungen erm&#246;glicht.
Struktur der Flagelle
Eine bakterielle Flagelle besteht aus drei Hauptkomponenten: dem Filament, dem Haken und dem Basalk&#246;rper. Das Filament ist eine lange, helikale Struktur, die aus sich wiederholenden Untereinheiten des Proteins Flagellin besteht und in ihrem Inneren hohl ist. Es dient als prim&#228;res Antriebselement. Der Haken verbindet das Filament mit dem Basalk&#246;rper und fungiert als flexible Kupplung, die das Drehmoment des Motors auf die Rotation des Filaments &#252;bertr&#228;gt. Der Basalk&#246;rper, oder auch Motorkomplex verankert die Flagelle in der Zellh&#252;lle des Bakteriums und weist zwischen gramnegativen und grampositiven Bakterien strukturelle Unterschiede auf. Bei gramnegativen Bakterien besteht der Basalk&#246;rper aus vier Ringen: dem L-Ring (verankert in der &#228;u&#223;eren Lipopolysaccharidschicht), dem P-Ring (eingebettet in die Peptidoglykanschicht) sowie den MS- und C-Ringen (lokalisiert in der Plasmamembran bzw. im Zytoplasma). Grampositive Bakterien hingegen besitzen aufgrund ihrer dickeren Peptidoglykanschicht und dem Fehlen einer &#228;u&#223;eren Membran nur die MS- und C-Ringe. Ein zentraler Stab verbindet diese Ringe und bildet das Kernst&#252;ck des Basalk&#246;rpers.
Mechanismus der Rotation und Motilit&#228;t
Der Basalk&#246;rper dient als rotierender Motor, der durch die protonenmotorische Kraft (PMK) angetrieben wird. Die PMK entsteht durch den Transport von Protonen durch die bakterielle Membran, wobei ein elektrochemischer Gradient aufgebaut wird. Wenn Protonen durch assoziierte Proteine wieder in die Zelle zur&#252;ckflie&#223;en, wird die dabei freigesetzte Energie zur Rotation der Flagelle genutzt. Diese Rotation kann mehrere hundert Umdrehungen pro Sekunde erreichen und bewegt das Bakterium durch fl&#252;ssige Umgebungen.
Rolle bei der Chemotaxis
Flagellen erm&#246;glichen den Prozess der bakteriellen Chemotaxis, w&#228;hrend dessen Zellen vorteilhafte Umgebungen aufsuchen oder sch&#228;dlichen Bedingungen entkommen. Dies geschieht durch zeitliches Erfassen chemischer Gradienten, wobei das Bakterium die Richtung und Frequenz der Flagellenrotation anpasst. Eine gegen den Uhrzeigersinn gerichtete Rotation f&#252;hrt zu einer gleichm&#228;&#223;igen, gerichteten Bewegung, w&#228;hrend die Rotation im Uhrzeigersinn ein Taumeln ausl&#246;st, wodurch die Zelle ihre Ausrichtung &#228;ndert.
Die Motilit&#228;t und Chemotaxis sind f&#252;r das &#220;berleben von Bakterien essentiell, da sie den Zugang zu N&#228;hrstoffen, die Kolonisierung von Wirtsgewebe und das Ausweichen vor ung&#252;nstigen Bedingungen erm&#246;glichen. Diese Anpassungsf&#228;higkeit unterstreicht die evolution&#228;re Bedeutung der Flagellen im mikrobiellen Leben.

Flagellen und Motilität bei Bakterien

Flagellen sind spezialisierte, fadenartige Strukturen, die aus der Zellh&#252;lle von Bakterien hervorragen. Sie spielen eine entscheidende Rolle bei der ...

Education

Lehre

JoVE Core

Microbiology

Mikrobiologie

Unit

Einheit

Microbial Cell Structure and Function        

Mikrobielle Zellstruktur und Funktion

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

bacterial flagella as tiny rotary motors

Bacterial flagella are thread-like structures that help cells move and respond to their surroundings. They extend from the cell envelope and support both motility and chemotaxis, which is the ability to move in response to chemical signals. Their design shows how bacteria use specialized structures to survive in different environments.

A flagellum has three main parts: the filament, the hook, and the basal body. The filament is the long, helical part made of repeating flagellin protein subunits, and it is hollow at the center. The hook acts as a flexible connector that passes torque from the motor to the filament.

The basal body anchors the flagellum inside the bacterial cell envelope. Its structure differs between Gram-negative and Gram-positive bacteria. Gram-negative bacteria have four rings: the L ring in the outer lipopolysaccharide layer, the P ring in the peptidoglycan layer, and the MS and C rings in the plasma membrane and cytoplasm. Gram-positive bacteria have a thicker peptidoglycan layer and no outer membrane, so they have only the MS and C rings. A central rod connects the rings and forms the core of the motor.

The basal body works as a rotary motor powered by the proton motive force, or PMF. PMF is an electrochemical gradient made by moving protons across the bacterial membrane. When protons flow back through motor proteins linked to the basal body, the released energy drives flagellar rotation. This rotation can reach several hundred revolutions per second and pushes the bacterium through liquid.

Flagella also help bacteria perform chemotaxis. Cells sense chemical gradients over time and change how often and in which direction the flagellum rotates. Counterclockwise rotation produces a smooth run, while clockwise rotation causes a tumble that reorients the cell. This movement helps bacteria reach nutrients, colonize host environments, and avoid harmful conditions.

Bacterial Flagella as Tiny Rotary Motors

prokaryotic vs. eukaryotic cells

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archaeal cell wall

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peptidoglycan synthesis

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outer layers of the cell envelope

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flagella and motility in bacteria

Bacterial flagella are thread-like structures that help cells move and respond to their surroundings. They extend from the cell envelope and support both motility and chemotaxis, which is the ability to move in response to chemical signals. Their design shows how bacteria use specialized structures to survive in different environments. A flagellum has three main parts: the filament, the hook, and the basal body. The filament is the long, helical part made of repeating flagellin protein...

fimbriae, pili, and axial filaments

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cell inclusions

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endospores and sporulation

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nucleoid

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Prokaryotes organize their DNA in the nucleoid, a distinct region where genetic material and associated proteins are packed. Because prokaryotic cells do not have a membrane-bound nucleus, the nucleoid helps keep DNA organized and available for cell activities. In most bacteria and archaea, the DNA is a single, circular, double-stranded molecule that is tightly compacted by supercoiling and protein interactions. Nucleoid-associated proteins, or NAPs, help shape and maintain this DNA region.

surface appendages of archaea

Archaeal Pili and Archaella in Action

Archaeal pili and archaella help archaea survive, attach, and move in challenging environments. These surface appendages support adhesion, biofilm formation, and motility. They give archaeal cells key advantages in habitats that can be extreme. Pili are filament-like structures made from pilin protein subunits. Their main role is adhesion, which means helping cells stick to surfaces. They also support biofilm formation, where cells live in a shared, surface-attached community. Some pili are...

key terms and concepts

Learn how bacterial flagella work as rotary motors, how Gram-negative and Gram-positive cells differ, and how runs and tumbles guide chemotaxis.

Bacterial Flagella as Tiny Rotary Motors | JoVE K12

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BIO.4.e

Bacterial Flagella as Tiny Rotary Motors

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