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

Os flagelos são apêndices finos e semelhantes a fios que se estendem da membrana plasmática e da parede celular que ajudam as bactérias na motilidade. O flagelo tem três partes principais - o filamento, o gancho e o corpo basal. O filamento, a parte visível do flagelo, é composto por subunidades de proteína flagelina dispostas em cadeias helicoidais. Ele é conectado ao seu corpo basal pelo gancho. O corpo basal consiste em uma haste central que passa por uma série de anéis de proteína. As bactérias Gram-negativas têm quatro anéis corporais basais. O anel L é ancorado à camada de lipopolissacarídeo, o anel P é incorporado à camada de peptidoglicano e os anéis MS e C estão ligados à membrana plasmática e ao citoplasma, respectivamente. O corpo basal das bactérias Gram-positivas contém apenas os anéis MS e C. O corpo basal funciona como um motor alimentado pela força motriz do próton, permitindo que o flagelo gire e permitindo que as bactérias se impulsionem. Além da motilidade, os flagelos ajudam as bactérias a se ligarem às superfícies e, em algumas bactérias, contribuem para a virulência, auxiliando na infecção.

flagelos e motilidade em bactérias

Os flagelos s&#227;o estruturas especializadas, semelhantes a filamentos, que se estendem a partir do envelope celular bacteriano. Eles desempenham um papel crucial na motilidade e na quimiotaxia. Sua organiza&#231;&#227;o estrutural e funcionamento exemplificam uma engenharia biol&#243;gica sofisticada, permitindo a sobreviv&#234;ncia e a adaptabilidade bacteriana em ambientes diversos.
Estrutura do Flagelo
Um flagelo bacteriano &#233; constitu&#237;do por tr&#234;s componentes principais: o filamento, o gancho e o corpo basal. O filamento, uma estrutura helicoidal longa composta por subunidades repetidas da prote&#237;na flagelina e oco em seu n&#250;cleo, atua como o principal elemento propulsor. O gancho conecta o filamento ao corpo basal, funcionando como um acoplamento flex&#237;vel que transmite o torque do motor para a rota&#231;&#227;o do filamento.
O corpo basal serve de &#226;ncora para o flagelo no envelope celular da bact&#233;ria e apresenta diversidade estrutural entre bact&#233;rias Gram-negativas e Gram-positivas. Nas bact&#233;rias Gram-negativas, o corpo basal &#233; composto por quatro an&#233;is: o anel L (ancorado na camada externa de lipopolissacar&#237;deos), o anel P (embutido na camada de peptideoglicano), e os an&#233;is MS e C (localizados na membrana plasm&#225;tica e no citoplasma, respectivamente). Por outro lado, as bact&#233;rias Gram-positivas, com sua camada mais espessa de peptideoglicano e aus&#234;ncia de membrana externa, possuem apenas os an&#233;is MS e C. Um bast&#227;o central conecta esses an&#233;is, formando o n&#250;cleo do aparato motor.
Mecanismo de Rota&#231;&#227;o e Motilidade
O corpo basal atua como um motor rotativo movido pela for&#231;a motriz de pr&#243;tons (PMF, do ingl&#234;s proton motive force). A PMF &#233; gerada pela transloca&#231;&#227;o de pr&#243;tons atrav&#233;s da membrana bacteriana, criando um gradiente eletroqu&#237;mico. &#192; medida que os pr&#243;tons retornam &#224; c&#233;lula por meio das prote&#237;nas motoras associadas ao corpo basal, a energia liberada impulsiona a rota&#231;&#227;o do flagelo. Essa rota&#231;&#227;o, que pode atingir v&#225;rias centenas de voltas por segundo, propulsiona a bact&#233;ria em ambientes l&#237;quidos.
Papel na Quimiotaxia
Os flagelos possibilitam a quimiotaxia bacteriana, um processo que permite &#224;s c&#233;lulas se movimentarem em dire&#231;&#227;o a ambientes favor&#225;veis ou evitarem condi&#231;&#245;es nocivas. Isso &#233; realizado por meio da detec&#231;&#227;o temporal de gradientes qu&#237;micos, com a bact&#233;ria ajustando a dire&#231;&#227;o e a frequ&#234;ncia da rota&#231;&#227;o flagelar. A rota&#231;&#227;o no sentido anti-hor&#225;rio resulta em um movimento cont&#237;nuo e direcionado conhecido como &#8220;corrida&#8221;, enquanto a rota&#231;&#227;o no sentido hor&#225;rio induz uma &#8220;turbilh&#227;o&#8221;, que reorienta a c&#233;lula.
A motilidade flagelar e a quimiotaxia s&#227;o vitais para a sobreviv&#234;ncia bacteriana, permitindo o acesso a nutrientes, a coloniza&#231;&#227;o de ambientes hospedeiros e a evas&#227;o de condi&#231;&#245;es adversas. Essa adaptabilidade ressalta a import&#226;ncia evolutiva dos flagelos na vida microbiana.

Flagelos e Motilidade em Bactérias

Os flagelos s&#227;o estruturas especializadas, semelhantes a filamentos, que se estendem a partir do envelope celular bacteriano. Eles desempenham um ...

Education

JoVE Core

Microbiology

Microbiologia

Unit

Unidade

Microbial Cell Structure and Function        

Estrutura e Função da Célula Microbiana

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

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

Cell Organization in Prokaryotes and Eukaryotes

Prokaryotic and eukaryotic cells show two major patterns of cell organization. These differences shape the structure, size, and function of living things across the domains of life. Prokaryotic cells, such as bacteria and archaea, are simple in structure. They do not have a nucleus or other membrane-bound organelles. Their DNA is usually a single circular molecule found in the nucleoid region, which is not surrounded by a nuclear membrane. Prokaryotes are usually very small, about 0.1 to 5.0...

microbial morphologies 

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bacterial cell wall 

Gram-Positive and Gram-Negative Walls

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archaeal cell wall

Archaeal Cell Wall Types and Functions

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peptidoglycan synthesis

Building the Bacterial Cell Wall

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plasma membrane in bacteria and archaea

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outer layers of the cell envelope

Capsules, Slime Layers, and S-Layers

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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

How Bacteria Stick, Share Genes, and Move

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cell inclusions

Prokaryotic Cell Storage Inclusions

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endospores and sporulation

How Bacteria Survive with Endospores

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nucleoid

How Prokaryotes Organize DNA

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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