Name: microbial oxygen needs and tolerance
Uploaded: 2025-07-28T10:52:33.000Z
Duration: 1 min 29 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.b

Oxygen Requirements and Growth Patterns

En función de las necesidades de oxígeno, los microorganismos se clasifican en varias clases.Los aerobios obligados, como las micobacterias, necesitan oxígeno, mientras que los anaerobios obligados, como los Clostridia, se ven perjudicados por él y dependen de la respiración anaeróbica para obtener energía.Los anaerobios facultativos como E. coli cambian entre el metabolismo aeróbico y el anaeróbico, pero crecen más rápido en presencia de oxígeno.Los microaerófilos, como el Helicobacter, requieren oxígeno en concentraciones inferiores a las atmosféricas.Los anaerobios aerotolerantes, como los lactobacilos, no utilizan oxígeno, pero pueden tolerarlo.En un medio líquido, el oxígeno forma un gradiente de concentración de arriba a abajo, guiando los patrones de crecimiento.Los aerobios obligados ocupan la superficie, los anaerobios se asientan en la parte inferior, los anaerobios facultativos se agrupan cerca de la parte superior, los microaerófilos forman una capa subsuperficial y los organismos aerotolerantes se distribuyen uniformemente.Durante el metabolismo del oxígeno, se producen subproductos tóxicos como el peróxido de hidrógeno y los radicales superóxido. Los aerobios y los anaerobios aerotolerantes los neutralizan con enzimas como la superóxido dismutasa y la peroxidasa.Por el contrario, los anaerobios estrictos carecen de estas enzimas, lo que los hace altamente sensibles al oxígeno.

requisitos de oxígeno y patrones de crecimiento

Los microorganismos presentan una amplia variedad de requerimientos de ox&#237;geno y patrones de crecimiento determinados por sus estrategias metab&#243;licas y adaptaciones al entorno. El ox&#237;geno, aunque esencial para muchos organismos, puede resultar t&#243;xico en determinadas condiciones, lo que influye en c&#243;mo crecen y sobreviven los microorganismos.
Requerimientos de ox&#237;geno de los microorganismos
Los microorganismos se clasifican en funci&#243;n de su capacidad para utilizar o tolerar el ox&#237;geno:
<ul>
<li>Los aerobios obligados, como Mycobacterium tuberculosis, necesitan ox&#237;geno para la producci&#243;n de energ&#237;a, ya que act&#250;a como aceptor final de electrones en la respiraci&#243;n aer&#243;bica. Estos organismos prosperan en ambientes ricos en ox&#237;geno.</li>
<li>Los anaerobios obligados, como Clostridium botulinum, son altamente sensibles al ox&#237;geno porque carecen por completo de enzimas neutralizadoras de especies reactivas de ox&#237;geno (ROS), como la catalasa, la super&#243;xido dismutasa y la peroxidasa, o bien las producen en cantidades insuficientes. Sin una defensa enzim&#225;tica adecuada, estos microorganismos no pueden neutralizar de forma eficaz las especies reactivas de ox&#237;geno, como el per&#243;xido de hidr&#243;geno y los radicales super&#243;xido generados durante la respiraci&#243;n.</li>
<li>Escherichia coli y otros anaerobios facultativos son vers&#225;tiles. Utilizan ox&#237;geno cuando est&#225; disponible, pero cambian a fermentaci&#243;n o respiraci&#243;n anaer&#243;bica en su ausencia.</li>
<li>Los microaer&#243;filos, como Helicobacter pylori, requieren ox&#237;geno a bajas concentraciones. Estos microorganismos presentan enzimas sensibles al O_2, lo que hace que la desintoxicaci&#243;n de ROS sea menos eficaz a concentraciones elevadas de ox&#237;geno.</li>
<li>Los anaerobios aerotolerantes, como la mayor&#237;a de las especies de Lactobacillus, no utilizan ox&#237;geno, pero pueden sobrevivir en su presencia gracias a la neutralizaci&#243;n de ROS mediante enzimas protectoras.</li>
</ul>
Patrones de crecimiento y t&#233;cnicas de cultivo
En estudios de laboratorio, el crecimiento de microorganismos bajo diferentes niveles de ox&#237;geno se demuestra frecuentemente utilizando caldo de tioglicolato, un medio que contiene agentes reductores como tioglicolato o ciste&#237;na. Estos compuestos eliminan el ox&#237;geno disuelto al reducirlo qu&#237;micamente a agua, creando un gradiente de ox&#237;geno en el medio:
<ul>
<li>Los aerobios obligados crecen en la superficie, donde la concentraci&#243;n de ox&#237;geno es mayor.</li>
<li>Los anaerobios obligados crecen en el fondo, donde no hay ox&#237;geno.</li>
<li>Los anaerobios facultativos crecen en todo el medio, pero predominan cerca de la superficie.</li>
<li>Los microaer&#243;filos crecen justo por debajo de la superficie.</li>
<li>Los anaerobios aerotolerantes crecen de forma uniforme, independientemente de los niveles de ox&#237;geno.</li>
</ul>
Otras t&#233;cnicas de cultivo anaerobio incluyen sistemas generadores de gas y c&#225;maras selladas para mantener ambientes libres de ox&#237;geno.
Toxicidad del ox&#237;geno y mecanismos de defensa
La presencia de ox&#237;geno provoca la formaci&#243;n de ROS, que pueden da&#241;ar componentes celulares esenciales. Los radicales hidroxilo inducen roturas de cadenas y mutaciones en el ADN. Las ROS oxidan y desnaturalizan enzimas, alterando su funci&#243;n. La peroxidaci&#243;n da&#241;a las membranas celulares, comprometiendo su integridad.
Sin embargo, los microorganismos aerobios y aerotolerantes neutralizan las ROS mediante diversas enzimas, como:
<ul>
<li>Catalasa: descompone el per&#243;xido de hidr&#243;geno en agua y ox&#237;geno.</li>
<li>Super&#243;xido dismutasa (SOD): convierte los radicales super&#243;xido en per&#243;xido de hidr&#243;geno.</li>
<li>Peroxidasa: reduce el per&#243;xido de hidr&#243;geno a agua.</li>
</ul>
En los anaerobios obligados, la ausencia de estas enzimas los hace altamente sensibles a la exposici&#243;n al ox&#237;geno.
Conclusi&#243;n
Comprender los requerimientos de ox&#237;geno de los microorganismos es esencial en campos como la medicina, donde las infecciones anaer&#243;bicas requieren estrategias terap&#233;uticas espec&#237;ficas, y en la microbiolog&#237;a industrial, donde optimizar las condiciones de crecimiento es crucial para los procesos de producci&#243;n.

Requisitos de oxígeno y patrones de crecimiento

Los microorganismos presentan una amplia variedad de requerimientos de ox&#237;geno y patrones de crecimiento determinados por sus estrategias ...

Education

Educación

JoVE Core

Microbiology

Microbiología

Unit

Unidad

Microbial Growth      

Crecimiento microbiano

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

microbial oxygen needs and tolerance

Microbial oxygen needs and tolerance shape how bacteria grow and survive. Oxygen can support energy production in some microorganisms, but it can also become harmful in certain environments. These differences help explain why microbes live in very specific places.

Microorganisms are grouped by how they use oxygen. Obligate aerobes, such as Mycobacterium tuberculosis, need oxygen because it serves as the terminal electron acceptor in aerobic respiration. Obligate anaerobes, such as Clostridium botulinum, are highly sensitive to oxygen because they lack enough protective enzymes or may not have them at all.

Facultative anaerobes, such as Escherichia coli, are flexible. They use oxygen when it is present, but they can switch to fermentation or anaerobic respiration when oxygen is missing. Microaerophiles, such as Helicobacter pylori, need oxygen at low levels. Aerotolerant anaerobes, such as most Lactobacillus species, do not use oxygen, but they can survive in it.

In the lab, thioglycollate broth is often used to show these growth patterns. This medium contains reducing agents such as thioglycollate or cysteine, which remove dissolved oxygen by reducing it to water. That creates an oxygen gradient in the tube. Obligate aerobes grow near the surface, obligate anaerobes grow at the bottom, facultative anaerobes grow throughout but most near the top, microaerophiles grow just below the surface, and aerotolerant anaerobes grow evenly.

Other anaerobic culture methods also help keep oxygen out. These include gas-generating systems and sealed chambers. Scientists use these tools to study microbes that need low-oxygen or oxygen-free conditions.

Oxygen can also cause toxicity because it leads to reactive oxygen species, or ROS. These harmful molecules can damage DNA, enzymes, and cell membranes. Hydroxyl radicals can cause strand breaks and mutations, ROS can oxidize and denature enzymes, and peroxidation can damage membranes.

Many aerobic and aerotolerant microorganisms defend themselves with enzymes. Catalase breaks hydrogen peroxide into water and oxygen. Superoxide dismutase, or SOD, converts superoxide radicals into hydrogen peroxide. Peroxidase then reduces hydrogen peroxide into water. Obligate anaerobes are especially vulnerable to oxygen because they lack these defenses or make too little of them.

Understanding microbial oxygen requirements matters in medicine and industrial microbiology. It helps explain why anaerobic infections need special treatment. It also helps scientists choose the best growth conditions for production and research.

Microbial Oxygen Needs and Tolerance

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microbial growth measurement: indirect methods

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factors influencing microbial growth: temperature

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oxygen requirements and growth patterns

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biofilms

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key terms and concepts

Learn how microbes use or avoid oxygen, from obligate aerobes to anaerobes. Explore thioglycollate broth, ROS damage, and oxygen defense enzymes.

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BIO.4.e

Microbial Oxygen Needs and Tolerance

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