Name: how scientists identify bacteria and fungi
Uploaded: 2019-01-29T11:04:46.000Z
Duration: 5 min 6 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

ecosystems-interactions-energy-and-dynamics

Ecosystems: Interactions, Energy And Dynamics

HS-LS2-7

Microbial and Fungal Diversity

Los microorganismos se definen como formas de vida demasiado pequeñas para verlas a simple vista. Pero aunque normalmente no los vemos, los microbios están en todas partes, haciendo cosas buenas como ayudar a nuestra digestión o hacer yogures y vino, hasta cosas no tan buenas como causar infecciones o enfermedades. 
Hablando de infecciones, en 1928, Alexander Fleming regresó a su laboratorio de vacaciones y notó una extraña contaminación de hongos en una de sus placas de cultivo bacteriano. Curiosamente, las colonias bacterianas inmediatamente alrededor de la contaminación habían sido destruidas. Esta observación condujo a muchas más investigaciones, que finalmente culminaron en el desarrollo de la penicilina y otros antibióticos que podrían tratar las infecciones bacterianas. Sin embargo, aunque pueden vivir uno al lado del otro en el mundo microscópico, sabemos por el estudio de sus formas y filogenias que las bacterias y los hongos son organismos muy diferentes y diversos. Repasemos brevemente algunas de las características definitorias de estos dos grupos principales. 
Las bacterias son procariotas unicelulares, es decir, son organismos unicelulares sin núcleo. Todas las bacterias tienen una pared celular, pero su composición y grosor varían. Las bacterias Gram positivas tienen una pared celular con una gruesa capa de peptidoglicano, que retiene fácilmente las moléculas de color violeta cristalino en la tinción de Gram. Sin embargo, las bacterias gramnegativas tienen una pared celular delgada rodeada por una membrana externa de lipopolisacárido, y solo conservan la contratinción, la safranina de color rojo. La tinción de Gram también permite la observación de formas bacterianas. Las bacterias redondas se llaman cocos. Las bacterias en forma de bastoncillos se llaman bacilos. Y las bacterias en forma de espiral se llaman espirilla. Además, las colonias bacterianas también se pueden caracterizar a simple vista, utilizando rasgos como el color, la forma y el tamaño de la colonia. 
Ahora, echemos un vistazo a los hongos. A diferencia de las bacterias, los hongos son eucariotas y, por lo tanto, sus células tienen orgánulos unidos a la membrana y un núcleo. Por lo general, se clasifican en grupos en función de sus estrategias reproductivas. Por ejemplo, los Ascomycota, u hongos de saco, que incluyen colmenillas, penicillium y trufas, tienen cuerpos fructíferos llamados ascocarpos. Las colmenillas están llenas de estas estructuras. Si los observamos más de cerca, contienen muchas estructuras más pequeñas llamadas ascos, que a su vez contienen muchas ascosporas formadas durante la reproducción sexual. Sin embargo, los Ascomycota a menudo se reproducen asexualmente por gemación. El segundo grupo importante de hongos que examinaremos es el Basidiomycota, u hongos de club. La mayoría de los hongos comestibles y venenosos en el bosque son en realidad estructuras reproductivas de la Basidiomycota. En este grupo, lo que denominaríamos el sombrero del hongo se conoce técnicamente como basidiocarpo. En los hongos con branquias, las branquias debajo del basidiocarpo están revestidas con estructuras diminutas conocidas como basidios, y estas producen basidiosporas, esporas reproductivas microscópicas, durante la reproducción sexual. Estas esporas suelen ser dispersadas por el viento, de forma similar a muchas semillas de plantas. Aquí, hemos examinado varios grupos principales de bacterias y hongos, y las características que los definen de una manera muy simplificada. Sin embargo, debido a la gran cantidad de especies microbianas, más de un billón según muchas estimaciones, los científicos a menudo las identifican y agrupan utilizando métodos adicionales, incluido el examen de su ADN. 
En este laboratorio, identificará diferentes especies de bacterias mediante tinción de Gram y examinará las características de la colonia. También examinará las especies de hongos para identificar sus estructuras reproductivas.

diversidad microbiana y fúngica

Las bacterias y los hongos son dos grupos muy diversos de organismos que pueden tener importantes efectos beneficiosos o perjudiciales en la salud humana. Por esta razón, es importante comprender y distinguir entre las especies individuales de estos grupos. Como recordará, los taxónomos biológicos agrupan los organismos en función de su relación filogenética. Los tres dominios de la vida, Bacterias, Arqueas y Eucariotas, segregan la vida en tres grupos distintos. Mientras que todas las bacterias caen dentro del dominio Bacterias, los hongos se encuentran en el dominio Eukaryota (Hongos del Reino). Además de las arqueas, las bacterias del dominio incluyen exclusivamente procariotas unicelulares, lo que significa que sus células carecen tanto de membrana nuclear como de orgánulos unidos a la membrana. Por el contrario, los hongos del dominio Eukaryota tienen orgánulos unidos a la membrana e incluyen organismos unicelulares y pluricelulares.
<h4>Gérmenes</h4>
Las bacterias se encuentran en casi todas partes de la Tierra y están muy adaptadas a los entornos en los que crecen. Como resultado, este dominio incluye una cantidad asombrosa de diversidad. El impacto de estos organismos en la salud humana es igualmente diverso. Por ejemplo, especies como el Streptococcus thermophilus pueden utilizarse para producir alimentos fermentados como el yogur, mientras que las esporas de la bacteria Bacillus anthracis son responsables de la enfermedad potencialmente mortal del ántrax.
Para ayudar en la identificación de dicho organismo, los microbiólogos han desarrollado una miríada de pruebas para caracterizar tanto células individuales como colonias enteras de bacterias. Uno de los métodos más comunes para identificar bacterias es la tinción de Gram. Esta prueba utiliza tintes de colores para determinar la composición de la pared celular de la bacteria. Las bacterias grampositivas, que tienen una pared celular gruesa formada por una proteína llamada peptidoglicano, retienen un tinte llamado violeta cristalino y, por lo tanto, aparecen de color púrpura. Por el contrario, las bacterias gramnegativas tienen una pared celular más delgada sin peptidoglicano y no retienen el cristal violeta. En cambio, estas células aparecen rosadas debido a una contratinción llamada safranina. El uso de la tinción de Gram a menudo sirve como un paso preliminar en la identificación de una especie bacteriana. La clasificación adicional requiere la identificación de características adicionales. Esto puede incluir la forma de las bacterias individuales, que pueden ser cocos (redondos), espirillos (espirales) o bacilos (en forma de bastoncillos). Además, el color, la forma, el brillo, la textura e incluso el olor de las colonias bacterianas se pueden utilizar para distinguir entre especies.
<h4>Hongos</h4>
Los hongos del dominio Eukaryota también son muy diversos ecológicamente y pueden variar en tamaño desde levaduras microscópicas hasta el organismo más grande de la tierra, el hongo de la miel (Armillaria ostoyae). Todos los hongos son heterótrofos, lo que significa que deben adquirir su alimento del medio ambiente. Estos organismos también exhiben diversidad en sus actividades específicas, nichos y efectos potenciales en la salud humana. Por ejemplo, algunos hongos son consumidos o utilizados para producir alimentos por los seres humanos, mientras que otros pueden causar infecciones graves o incluso mortales.
Dentro del reino de los hongos, existen dos divisiones taxonómicas distintas basadas en la estrategia reproductiva de la especie. En primer lugar, los Ascomycota, conocidos como hongos del saco, tienen una estructura reproductiva llamada ascus. Juntos, muchos ascos forman el ascocarpo, o "cuerpo fructífero" de los hongos. Estos hongos pueden reproducirse sexual o asexualmente por gemación. Los ascomycota consisten en algunas especies económicamente importantes, como la levadura utilizada en la elaboración de cerveza y hornear pan, y algunas especies populares en la cocina, como las colmenillas y las trufas. El segundo grupo, Basidiomycota, incluye organismos comúnmente conocidos como "hongos club" debido a la presencia de una gran estructura reproductiva en forma de garrote llamada basidio. A diferencia de Ascomycota, la mayoría de los Basidomucota se reproducen exclusivamente por reproducción sexual. Esto ocurre cuando dos micelios haploides se unen para formar un basidiocarpo. En un champiñón, esta es la estructura de la tapa. En la parte inferior del basidiocarpo, estructuras reproductivas llamadas branquias revestidas con estructuras llamadas basidios producen núcleos haploides que eventualmente forman basidiosporas. Las basidiosporas son dispersadas por el viento. Esta división taxonómica incluye muchos champiñones que se comen comúnmente, así como hongos silvestres.
<h4>Importancia de la microbiología</h4>
En general, está claro que las diversas funciones y propiedades de los microorganismos hacen que su identificación sea extremadamente importante para la salud y el bienestar humanos. Si bien hasta la fecha se ha identificado un gran número de especies de hongos y bacterias, se estima que millones más aún no han sido identificadas y clasificadas. Además, las disciplinas humanas que exploran los hongos y las bacterias son tan diversas como los propios organismos y, sin duda, seguirán creciendo. La relevancia de los microorganismos en los campos de la medicina es más frecuente ahora que nunca, ya que las especies de bacterias infecciosas resistentes a múltiples antibióticos amenazan la salud humana. La comprensión de la estructura y las características biológicas de las especies infecciosas y no infecciosas proporciona información clave necesaria para la creación de nuevos tratamientos antibióticos y estrategias preventivas3-4.
La microbiología también es fundamental para la industria alimentaria. Numerosos productos, como el yogur, el queso, la kombucha, el pan y el alcohol, se elaboran utilizando categorías o especies específicas de microbios. Al mismo tiempo, los científicos de alimentos se centran en la ingeniería de compuestos químicos y conservantes que reducirán el crecimiento de microbios no deseados en los alimentos. En todos estos procesos, es necesario comprender cómo los microbios sobreviven, se reproducen y afectan a su entorno.
<h4>Referencias </h4>
<ol class="referencias">
	<li>Hiroshi Asakura, Holger Brueggemann, Sou-ichi Makino y Yoshiko Sugita-Konishi, "Enfoques moleculares para la clasificación de patógenos microbianos de importancia para la salud pública", BioMed Research International, vol. 2014, ID de artículo 725801, 2 páginas, 2014. https://doi.org/10.1155/2014/725801.</li>
	<li>Treseder, K. K. y J. T. Lennon (2015). 'Rasgos fúngicos que impulsan la dinámica del ecosistema en tierra'. Microbiol Mol Biol Rev 79(2): 243-262.</li>
	<li>Arvanitis, M. y E. Mylonakis (2015). 'Interacciones fúngico-bacterianas y su relevancia en la salud'. Microbiol Celular 17(10): 1442-1446.</li>
	<li>Aarestrup, F. M., et al. (2008). «Resistencia en bacterias de la cadena alimentaria: epidemiología y estrategias de control». Expert Rev Anti Infect Ther 6(5): 733-750.</li>
</ol>

Diversidad microbiana y fúngica

Las bacterias y los hongos son dos grupos muy diversos de organismos que pueden tener importantes efectos beneficiosos o perjudiciales en la salud humana. Para ello...

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how scientists identify bacteria and fungi

Bacteria and fungi are highly diverse organisms, and scientists identify them by looking at their structure, growth, and role in health. Some species help people, while others can cause disease, so learning how to tell them apart matters in biology and medicine.

Biological taxonomists group organisms by evolutionary relatedness. Life is divided into three domains: Bacteria, Archaea, and Eukaryota. Bacteria belong to the domain Bacteria, which includes single-celled prokaryotes. Prokaryotic cells lack a nuclear membrane and membrane-bound organelles. Fungi belong to the domain Eukaryota, in Kingdom Fungi. They have membrane-bound organelles and can be either unicellular or multicellular.

Bacteria live almost everywhere on Earth, and their diversity is very large. This group includes helpful species such as Streptococcus thermophilus, which is used to make fermented foods like yogurt. It also includes harmful species such as Bacillus anthracis, whose spores cause anthrax. Microbiologists use several tests to identify bacteria. One common test is Gram staining, which uses colored dyes to show cell wall structure.

Gram-positive bacteria have a thick cell wall made of peptidoglycan, so they retain crystal violet and appear purple. Gram-negative bacteria have a thinner cell wall without peptidoglycan, so they do not keep crystal violet. Instead, they take up safranin and appear pink. Gram staining is often a first step in bacterial identification. Scientists then look at other traits, including cell shape. Cocci are round, spirillum are spiral, and bacilli are rod-shaped. Colony color, shape, sheen, texture, and even smell can also help distinguish species.

Fungi are also diverse and can range from microscopic yeast to the honey fungus, Armillaria ostoyae, which is the largest organism on Earth. Fungi are heterotrophic, which means they must get food from their environment. Some fungi are used in food production or are eaten by people, while others can cause severe or even deadly infections.

Within Kingdom Fungi, two major divisions are based on reproduction. Ascomycota are the sac fungi. They have a reproductive structure called an ascus, and many asci form an ascocarp, or fruiting body. These fungi can reproduce sexually or asexually by budding. This group includes yeast used in brewing beer and baking bread, as well as edible fungi like morels and truffles.

Basidiomycota are commonly called club fungi because they have a club-shaped basidium. Most Basidiomycota reproduce sexually. Two haploid mycelia join to form a basidiocarp, which is the cap of a button mushroom. On the underside, gills lined with basidia produce haploid nuclei that later form basidiospores. Wind spreads these spores. This group includes many button mushrooms and wild puff mushrooms.

Studying microbes is important for human health and for food production. Millions of species may still need to be identified and classified, and microbiology continues to grow as a field. This work is especially important now because multi-antibiotic-resistant bacteria can threaten human health. Knowing microbial structure and biology helps scientists develop new antibiotics and prevention strategies. Microbiology also supports the food industry, where microbes are used to make yogurt, cheese, kombucha, bread, and alcohol, while other compounds and preservatives are designed to limit unwanted microbial growth.

How Scientists Identify Bacteria and Fungi

how-scientists-identify-bacteria-and-fungi

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microbial and fungal diversity

Bacteria and fungi are highly diverse organisms, and scientists identify them by looking at their structure, growth, and role in health. Some species help people, while others can cause disease, so learning how to tell them apart matters in biology and medicine. Biological taxonomists group organisms by evolutionary relatedness. Life is divided into three domains: Bacteria, Archaea, and Eukaryota. Bacteria belong to the domain Bacteria, which includes single-celled prokaryotes. Prokaryotic...

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How Scientists Identify Bacteria and Fungi

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