Name: gram-positive and gram-negative walls
Uploaded: 2025-06-12T09:28:45.000Z
Duration: 1 min 22 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.c

Bacterial Cell Wall 

La pared celular bacteriana es una estructura rígida que rodea la membrana plasmática. Mantiene la forma de la célula y la protege de la presión osmótica. Está compuesto por peptidoglicano, un polímero de azúcares alternos, N-acetilglucosamina y ácido N-acetilmurámico, unidos por aminoácidos, formando una malla flexible. Las bacterias grampositivas tienen capas gruesas de peptidoglicano. También contienen ácidos teicoicos, que facilitan la absorción de iones y protegen las células de sustancias nocivas y moléculas de defensa del huésped. Las bacterias gramnegativas tienen una capa más delgada de peptidoglicano y una membrana externa con lipopolisacáridos, que tienen actividad de endotoxinas que desencadena la respuesta inmunitaria del huésped y proporciona integridad estructural. La tinción de Gram distingue a las bacterias por la estructura de la pared celular. Las bacterias grampositivas aparecen de color púrpura ya que conservan el tinte violeta cristalino, mientras que las bacterias gramnegativas aparecen de color rosa debido a una contratinción. La composición de la pared celular también determina la susceptibilidad a los antibióticos. Por ejemplo, las bacterias Gram-positivas son más susceptibles a la penicilina que las bacterias Gram-negativas.

pared celular bacteriana

La pared celular bacteriana es un componente estructural esencial que rodea la membrana plasm&#225;tica, preserva la integridad celular, determina la forma y protege contra el estr&#233;s osm&#243;tico. Esta estructura r&#237;gida pero flexible est&#225; compuesta principalmente por peptidoglicano, un pol&#237;mero que forma una matriz en forma de malla que confiere resistencia mec&#225;nica y flexibilidad.
Composici&#243;n y estructura del peptidoglicano
El peptidoglicano, el n&#250;cleo de la pared celular bacteriana, est&#225; compuesto por unidades alternas de N-acetilglucosamina (NAG) y &#225;cido N-acetilmur&#225;mico (NAM) interconectadas por cadenas cortas de amino&#225;cidos. Esta disposici&#243;n proporciona resistencia al estr&#233;s f&#237;sico y mantiene la forma de la c&#233;lula. El grosor y la composici&#243;n de la capa de peptidoglicano var&#237;an significativamente entre las bacterias Gram-positivas y Gram-negativas, lo que influye en sus propiedades f&#237;sicas y su susceptibilidad a los antibi&#243;ticos.
Paredes celulares Gram-positivas vs. Gram-negativas
Las bacterias Gram-positivas poseen una pared celular robusta con m&#250;ltiples capas de peptidoglicano. Dentro de esta estructura est&#225;n los &#225;cidos teicoicos, que juegan un papel en el transporte de cationes y en la defensa contra sustancias nocivas, incluidos los antibi&#243;ticos y las mol&#233;culas del sistema inmunol&#243;gico. Esta disposici&#243;n multicapa retiene el colorante cristal violeta durante el proceso de tinci&#243;n de Gram, lo que otorga a estas bacterias su caracter&#237;stico color morado.
En contraste, las bacterias Gram-negativas tienen una capa de peptidoglicano m&#225;s delgada, rodeada por una membrana externa rica en lipopolisac&#225;ridos (LPS). Esta membrana externa act&#250;a como una barrera selectiva, contribuyendo a la estabilidad estructural y funcionando como una endotoxina durante las infecciones. El proceso de tinci&#243;n de Gram resulta en bacterias Gram-negativas que aparecen de color rosa debido a la retenci&#243;n del contratinte en lugar del tinte primario.
Susceptibilidad a los antibi&#243;ticos y mecanismos
Las diferencias estructurales en las paredes celulares bacterianas determinan su interacci&#243;n con los antibi&#243;ticos. La penicilina y los antibi&#243;ticos relacionados con los beta-lact&#225;micos atacan la s&#237;ntesis de peptidoglicano, inhibiendo eficazmente la formaci&#243;n de la pared celular en las bacterias Gram-positivas. Aunque las bacterias Gram-negativas muestran resistencia intr&#237;nseca a algunos antibi&#243;ticos como la penicilina debido a su membrana externa, los antibi&#243;ticos beta-lact&#225;micos que penetran esta barrera siguen siendo efectivos. Comprender la composici&#243;n de la pared celular bacteriana es fundamental para desarrollar antibi&#243;ticos dirigidos y estudiar los mecanismos de resistencia bacteriana.

Pared celular bacteriana

La pared celular bacteriana es un componente estructural esencial que rodea la membrana plasm&#225;tica, preserva la integridad celular, determina la ...

Education

Educación

JoVE Core

Microbiology

Microbiología

Unit

Unidad

Microbial Cell Structure and Function        

Estructura y función de la célula microbiana

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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 thickness and makeup of this layer differ in Gram-positive and Gram-negative bacteria, which affects physical properties and antibiotic sensitivity.

Gram-positive bacteria have several layers of peptidoglycan in a thick wall. Teichoic acids are embedded in this structure and help with cation transport and defense against harmful substances, including antibiotics and immune molecules. This thick wall holds the crystal violet dye during Gram staining, so Gram-positive bacteria appear purple.

Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane rich in lipopolysaccharides, or LPS. This outer membrane acts as a selective barrier and adds structural support. It also acts as an endotoxin during infections. In Gram staining, Gram-negative bacteria appear pink because they keep the counterstain instead of the primary dye.

These wall differences also affect antibiotics. Penicillin and related beta-lactam antibiotics block peptidoglycan synthesis, so they can stop cell wall formation in Gram-positive bacteria. Gram-negative bacteria are naturally resistant to some antibiotics like penicillin because of their outer membrane. However, beta-lactam antibiotics that can pass through this barrier may still work. Learning cell wall structure helps explain targeted antibiotics and bacterial resistance.

Gram-Positive and Gram-Negative Walls

prokaryotic vs. eukaryotic cells

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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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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 

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

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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 as Tiny Rotary Motors

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fimbriae, pili, and axial filaments

How Bacteria Stick, Share Genes, and Move

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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

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

Compare Gram-positive and Gram-negative bacterial cell walls, from peptidoglycan and teichoic acids to Gram staining and antibiotic response.

Gram-Positive and Gram-Negative Walls | JoVE K12

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BIO.4.e

Gram-Positive and Gram-Negative Walls

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