Name: how prokaryotes organize dna
Uploaded: 2025-06-12T09:31:54.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.c

Nucleoid

O nucleóide é uma região distinta e livre de membrana nas células procarióticas que contém o DNA da célula e proteínas associadas. Na maioria das bactérias e archaea, o DNA é uma molécula única, circular e de fita dupla, altamente compactada por meio de superenrolamento e da ação de proteínas arquitetônicas chamadas proteínas associadas a nucleóides ou NAPs. Essas proteínas ajudam a organizar o DNA em domínios de interação cromossômica, garantindo estabilidade estrutural e tornando-o acessível para replicação, transcrição e reparo do DNA. Os NAPs também são cruciais para a divisão celular, ajudando a segregar os cromossomos em células-filhas. Em archaea Sulfolobus, o cromossomo ocupa dois compartimentos distintos, com regiões de alta e baixa expressão gênica. A coalescina, um NAP específico para archaea, ajuda a manter esses compartimentos distintos, garantindo a expressão de genes com base nas necessidades da célula. Muitas archaea usam proteínas semelhantes a histonas como NAPs para organizar seu DNA em estruturas semelhantes a nucleossomos semelhantes às dos eucariotos. No entanto, essas histonas podem formar tetrâmeros ou complexos maiores, diferindo da estrutura octamérica em células eucarióticas.

nucleoide

O nucleoide representa uma regi&#227;o estrutural e funcionalmente distinta dentro das c&#233;lulas procari&#243;ticas, onde se encontram o DNA e as prote&#237;nas associadas da c&#233;lula. Ao contr&#225;rio das c&#233;lulas eucari&#243;ticas, os procariontes n&#227;o possuem um n&#250;cleo delimitado por membrana, e o nucleoide facilita a organiza&#231;&#227;o e a acessibilidade do material gen&#233;tico dentro dessa limita&#231;&#227;o. O DNA na maioria das bact&#233;rias e arqueias existe como uma &#250;nica mol&#233;cula circular, de fita dupla, altamente compactada por superenovelamento e por intera&#231;&#245;es com prote&#237;nas especializadas.
Papel das Prote&#237;nas Associadas ao Nucleoide
As prote&#237;nas associadas ao nucleoide (NAPs, do ingl&#234;s *nucleoid-associated proteins*) desempenham um papel central na manuten&#231;&#227;o da estrutura do nucleoide. Essas prote&#237;nas s&#227;o essenciais para condensar o DNA em dom&#237;nios de intera&#231;&#227;o cromoss&#244;mica, estabilizar a arquitetura do nucleoide e garantir a acessibilidade do DNA para processos como transcri&#231;&#227;o, replica&#231;&#227;o e reparo. Al&#233;m do suporte estrutural, as NAPs s&#227;o fundamentais durante a divis&#227;o celular, facilitando a segrega&#231;&#227;o precisa dos cromossomos entre as c&#233;lulas-filhas.
Organiza&#231;&#227;o do Nucleoide em Arqueias
Em arqueias, o nucleoide apresenta um alto grau de complexidade organizacional. A arqueia *Sulfolobus* exemplifica essa complexidade ao segregar seus cromossomos em compartimentos distintos, caracterizados por regi&#245;es de alta e baixa express&#227;o g&#234;nica. A coalescina, uma NAP arqueana exclusiva, &#233; essencial para manter essa compartimentaliza&#231;&#227;o, permitindo uma regula&#231;&#227;o g&#234;nica din&#226;mica com base nas necessidades celulares.
Prote&#237;nas Semelhantes a Histonas em Arqueias
Muitas arqueias utilizam prote&#237;nas semelhantes &#224;s histonas para organizar ainda mais seu DNA em estruturas an&#225;logas aos nucleossomos, tra&#231;ando um paralelo com a organiza&#231;&#227;o da cromatina eucari&#243;tica. No entanto, as histonas arqueanas geralmente formam complexos tetram&#233;ricos ou maiores, em contraste com o n&#250;cleo octam&#233;rico das histonas eucari&#243;ticas. Essa varia&#231;&#227;o estrutural reflete a adapta&#231;&#227;o evolutiva das histonas arqueanas para compactar e regular o DNA em ambientes extremos, uma caracter&#237;stica marcante de muitas esp&#233;cies arqueanas.
Ao integrar NAPs, prote&#237;nas semelhantes a histonas e o superenovelamento, as c&#233;lulas procari&#243;ticas alcan&#231;am uma organiza&#231;&#227;o gen&#233;tica compacta, por&#233;m funcionalmente din&#226;mica, garantindo a express&#227;o g&#234;nica eficiente e a viabilidade celular.

Nucleoide

O nucleoide representa uma regi&#227;o estrutural e funcionalmente distinta dentro das c&#233;lulas procari&#243;ticas, onde se encontram o DNA e as ...

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

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. They condense DNA into chromosome interaction domains and support the nucleoid structure. NAPs also keep the DNA accessible for transcription, replication, and repair. During cell division, they help chromosomes separate correctly into daughter cells.

In archaea, nucleoid organization can be especially complex. The archaeon Sulfolobus separates its chromosomes into distinct compartments with areas of high and low gene expression. A unique archaeal NAP called coalescin helps maintain this compartmentalization and supports changes in gene activity as the cell needs them.

Many archaea also use histone-like proteins to organize DNA into nucleosome-like structures. This is similar to chromatin organization in eukaryotic cells, but archaeal histones often form tetramers or even larger complexes instead of the eukaryotic octameric core. Together with supercoiling and NAPs, these proteins help prokaryotic cells keep their genetic material compact, regulated, and ready for use.

How Prokaryotes Organize DNA

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 

Microbial Shapes and Cell Forms

Microbial shapes and cell forms help bacteria, archaea, and eukaryotic microbes survive in many environments. Cell shape affects how these organisms grow, take up nutrients, and handle waste. It also reflects the link between structure and function. Among bacteria, cocci and bacilli are the most common shapes. Cocci are spherical cells, and they may appear alone or in pairs called diplococci, chains called streptococci, clusters called staphylococci, or groups of four called tetrads. Bacilli...

bacterial cell wall 

Gram-Positive and Gram-Negative Walls

Bacterial cell walls give bacteria their shape and help protect them from osmotic stress. This rigid but flexible layer surrounds the plasma membrane and supports cellular integrity. Its main building block is peptidoglycan, a mesh-like polymer that adds strength while still allowing some flexibility. Peptidoglycan is made of alternating N-acetylglucosamine, or NAG, and N-acetylmuramic acid, or NAM. Short amino acid chains connect these sugar units and help form the strong network. The...

archaeal cell wall

Archaeal Cell Wall Types and Functions

Archaeal cell walls protect archaea and help them survive in extreme environments. Unlike bacterial cell walls, they do not have the peptidoglycan layer found in most bacteria. Instead, archaea use a range of materials, including proteins, polysaccharides, and pseudomurein, to build their outer layer. The most common archaeal cell wall is the S-layer, or surface layer. It is made of tightly packed protein or glycoprotein units that form a crystalline lattice. These repeating patterns can make...

peptidoglycan synthesis

Building the Bacterial Cell Wall

Peptidoglycan builds the bacterial cell wall and gives the cell its shape and strength. It is a mesh-like polymer around the bacterial plasma membrane. The polymer is made of repeating sugar units, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), linked by β-1,4 glycosidic bonds. Short peptide chains cross-link the sugar chains and make the wall more rigid. Peptidoglycan biosynthesis starts in the cytoplasm with soluble precursors. Uridine diphosphate, or UDP, binds to NAG and NAM to...

plasma membrane in bacteria and archaea

Bacterial vs Archaeal Membrane Lipids

Bacterial and archaeal plasma membranes control what enters and leaves the cell. They also help maintain cell integrity. Although both membranes do the same basic job, their structures are different because bacteria and archaea face different environmental demands. Bacterial plasma membranes are mainly made of phospholipids. These lipids have fatty acid chains linked to a glycerol backbone by ester bonds. They form a bilayer, with hydrophilic glycerol-phosphate heads facing outward and...

outer layers of the cell envelope

Capsules, Slime Layers, and S-Layers

Capsules, slime layers, and S-layers are outer coverings on prokaryotic cells. These layers help bacteria and archaea survive, attach to surfaces, and interact with their environment. They are often made of polysaccharides, polypeptides, proteins, or glycoproteins. Capsules are tightly bound and highly organized layers that stick firmly to the bacterial cell wall. They are usually made of polysaccharides, although some are made of polypeptides. A capsule protects cells from dehydration and can...

flagella and motility in bacteria

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...

fimbriae, pili, and axial filaments

How Bacteria Stick, Share Genes, and Move

Fimbriae, pili, and axial filaments are bacterial surface structures that help cells attach, exchange genes, and move. These hairlike appendages are made mainly of pilin protein. They support bacterial survival in different environments and can also increase pathogenicity. Fimbriae are fine, filament-like structures that are densely packed on the bacterial surface. They are about 2 to 10 nanometers wide and help bacteria attach to nonliving surfaces and to host tissues. This adhesion is an...

cell inclusions

Prokaryotic Cell Storage Inclusions

Prokaryotic cell storage inclusions help bacteria store nutrients, manage energy, and adapt to changing environments. These inclusions let cells survive when food, phosphate, sulfur, light, or oxygen levels change. They are important examples of how simple cells can still have highly specialized structures. Some inclusions store carbon. Poly-β-hydroxybutyric acid, or PHB, forms granules that act as a long-term carbon and energy reserve. Glycogen granules also store carbon, but they provide a...

endospores and sporulation

How Bacteria Survive with Endospores

Endospores help some bacteria survive harsh conditions. These dormant cells are made mainly by Gram-positive bacteria such as Bacillus and Clostridium. They are highly resistant to heat, ultraviolet and ionizing radiation, drying, and toxic chemicals. In rare cases, endospore-like structures have also been seen in some Gram-negative bacteria, including Coxiella burnetii and Sporosarcina ureae, as well as in other species exposed to extreme conditions. Sporulation begins when bacteria face...

nucleoid

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

Explore how the nucleoid, nucleoid-associated proteins, and archaeal histone-like proteins organize prokaryotic DNA for gene expression, replication, and cell division.

How Prokaryotes Organize DNA | 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.

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BIO.4.e

How Prokaryotes Organize DNA

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