“There is nothing more useful than salt and the sun.”

This saying, attributed to the Roman writer and soldier Pliny the Elder almost 2,000 years ago, highlights the importance that humanity has given since ancient times to one of the main products extracted from seawater.

The salt

The salt Pliny was referring to is a mineral formed by the union of two chemical elements, chlorine and sodium, and is the only rock we can eat directly.

Most salt is dissolved in the water of seas and oceans, and to extract it, we have developed different techniques, most of them based on natural evaporation and crystallization processes, such as those carried out in coastal salt mines, where millions of tons are extracted each year.

Coastal salt mines are very special ecosystems. Their location makes them a haven for numerous bird species, many of which establish their breeding, feeding, or wintering colonies here.

The waters surrounding the salt flats, which are the same from which the salt will later be extracted, are home to a coastal marine ecosystem inhabited by representatives of a vast array of organisms. They are home to oxygen-producing cyanobacteria that form green mats that cover the shallow sediments.

A characteristic of these cyanobacteria is that their filaments are constantly moving, and nematodes, perhaps the most abundant animals on the planet, roam among them.

Some mollusk species also find these waters an ideal place for their newly hatched larvae to enjoy the tranquility they need to develop.

Polychaete worms are abundant and colonize both the surface of the sediment and the shells of other animals while filtering the water in search of organic particles or tiny planktonic microorganisms, something that urochordates such as sea squirts also constantly do.

Here, it is also possible to find tiny and delicate microscopic jellyfish and a large number of crustaceans, both in their adult and larval stages.

This entire marine ecosystem changes radically when water enters the salt flats. And the striking colors displayed by the lagoons where the salt crystallizes are simply a reflection of the unique biodiversity they harbor. A biodiversity made up of an enormous number of microscopic organisms adapted to living in conditions of extreme salinity and sunlight.

One of these organisms, perhaps one of the most characteristic, is the alga Dunaliella salina, known precisely as the “salt flats algae.”

Dunaliella salina is the eukaryotic organism with the highest salt tolerance, and it is this tolerance that allows it to inhabit these waters, whose salt content can reach extreme levels. But this causes stress, and when that happens, it produces a substance to protect itself.

This protective substance is beta-carotene, which is precisely what gives it its striking red color.

Dunaliella also produces large quantities of another substance, glycerol, which it uses to regulate the salt concentration inside the cell.

However, Dunaliella‘s membrane is not impermeable, and much of the glycerol escapes into the environment, which constitutes an excellent food source for the multitude of bacteria with which it coexists.

And this is where a special relationship between the microorganisms that live in salt flats and salt production emerges.

The abundance of Dunaliella and bacteria causes the water to heat up more quickly and reach temperatures much higher than ambient temperatures. Furthermore, each of the bacteria can act as a nucleus for the formation of salt crystals, accelerating the process.

But not all salt flats are found on the coast. Some are also located inland, in areas far from the sea.

Ilargi Martínez-Ballesteros, principal investigator of the MikroIker group at the University of the Basque Country/Euskal Herriko Unibersitatea (UPV/EHU), tells us about these salt flats and her recent discoveries.

“We are in Salinas de Añana.

This salt flat is perhaps different from those we can find in other places on the Iberian Peninsula, for example, since its unique characteristic is that the brine used for salt production comes out through the presence of a diapir in this valley, in the Añana Salt Valley.

Various studies have analyzed the depth at which this diapir may be located. It is not known specifically, but it appears to be more than 200 meters deep. The water that filters through has underground contact with the halite found deep underground and dissolves it before reaching the surface through various springs in the valley.

A curious fact about this valley, which we have also seen strongly influences the presence of halophilic microorganisms in the brine water at this salt mine, is that just a few meters away, there are different springs with different salinities.

For example, there are two springs, one called El Pico and the other El Pico Dulce, located just a few meters apart, and the microorganism taxa we found there are completely different. This is due to their adaptation and because the amount of salt in the brine in the different springs is very different.

At Pico Dulce, we are talking about saline water, which has around 20-30 grams of salt per liter, and at El Pico, it reaches 230-240 grams of salt per liter—it is completely salty.

That vast difference is what we’ve seen primarily determines the presence of one type of halophile or another in the brine.

Another characteristic we’ve been discovering by studying the presence of genetic material, DNA, in the water through its extraction and sequencing is that we’ve been able to identify bacterial and archaeal populations that have been previously described, but we’ve still missed out on many sequences, a lot of DNA, that we haven’t been able to identify.

And yes, for now, we’ve discovered a new species that has been characterized here, in Salinas de Añana, in the brine of the main spring, the Santa Engracia Spring.

Perhaps microorganisms are living there that we don’t yet know about, and perhaps we’ll be able to isolate and observe them in the laboratory.

On the other hand, the study of halophiles is also interesting because it has been discovered that, thanks to the adaptations they have developed throughout their evolution to survive in these extreme salinity conditions, they produce different metabolites, products that may be of interest for biotechnological uses.

The new bacterium discovered in the Añana Salt Flats has been named Altererythrobacter muriae, and among its characteristics is its ability to live in water with a concentration of up to 200 grams of salt per liter, a characteristic that places it among the group of microorganisms considered halotolerant.

What does this bacteria feed on in the brine?

Altererythrobacter muriae does not carry out photosynthesis, does not have chlorophyll, and feeds on the organic matter present in the waters in which it lives, which is why it is considered a heteroorganotrophic organism.

Scientists have proven that Altererythrobacter muriae produces pigments called carotenoids.

What function do these pigments perform?

The main function of this pigment is to act as an antioxidant, preventing the damage that excess oxygen could cause to the bacteria.

Many of the microorganisms that inhabit inland salt marshes are considered extremophiles, since they have adapted to living in extreme environmental conditions. In this case, extreme salinity and, often, sunlight. But not all are extremophiles. Others, such as Halomonas, a bacteria common in these environments, are not extremophilic but halotolerant, meaning they are able to withstand the salinity typical of these waters, although it is not exclusive to them.

But… why are these inland waters salty? How did the salt get to these areas?

The thick layers of salt left behind by the disappearance of ancient seas transformed into a rock called halite, which forms what we now know as salt domes or diapirs.

Water circulating through underground aquifers passes through the diapir and dissolves it before exiting the surface with a high concentration of salt. This high concentration, combined with the increase in temperature caused by sunlight, causes the salts to begin to crystallize.

In addition to sodium chloride or common salt, which is the main component of halite, the rock that forms the diapir, water also dissolves other compounds as it passes through. Some of the most common are salts of elements such as calcium and magnesium, usually in the form of carbonates and sulfates.

You can see the beauty of the Añana Salt crystals forming at this link: https://www.youtube.com/watch?v=8wiI2X-J-vM
https://www.youtube.com/watch?v=8wiI2X-J-vM

In addition to the salt flats associated with diapirs, a special type of saline ecosystem occurs in the interior of continents. These are lagoons located in arid terrain, in areas where rainfall is very irregular and generally scarce. These wetlands are known as “las saladas.”

Salt marshes are what scientists call endorheic lagoons. This means they are lagoons that form in depressions in the ground because this is where rainwater accumulates. This water dissolves the salts that make up the rocks of the ground surrounding the lagoon before accumulating in the basin, from which it only emerges through evaporation caused by the sun.

It is within these salt waters that the Artemia salina, one of the animals most resistant to high salt concentrations, finds its ideal habitat. This crustacean whose morphology appears to have changed almost nothing since the Triassic period, which means it is extraordinarily well adapted to these unique and extreme environmental conditions. During the periods when the basins remain covered by water, the adult brine shrimp feed on the dense populations of microalgae and reproduce rapidly, often without the intervention of males, through a strategy called parthenogenesis.

But how do they survive long periods of drought?

The secret to their survival is a strategy called cryptobiosis, a kind of “hidden life.” When the water completely disappears, the eggs produced by the brine shrimp are trapped by the salt and exposed to the air and sun, where they can remain for a long time. Sometimes for more than ten years.

These are resistant eggs, which remain inactive until rainwater refills the lagoon. At that point, these eggs rehydrate, “awaken,” and hatch, releasing the new larvae that had remained dormant inside them in embryo form. In this way, these new generations reestablish brine shrimp populations in a seemingly endless cycle.

A natural cycle that has been in operation for more than 200 million years and is regulated by water and the concentration of one of the key elements in these ecosystems: salt.

You can watch the episode “The Salt of Life” (25 minutes. Original version in Spanish. Subtitled in English and Portuguese) from our series “Planet Microbe” at this link

https://caixaforumplus.org/v/la-sal-de-la-vida

La entrada The salt of Life se publicó primero en Science into Images.

“No hay nada más útil que la sal y el sol”

Esa sentencia, atribuida al escritor y militar romano Plinio el Viejo hace casi 2000 años, pone de manifiesto la importancia que la humanidad ha dado desde tiempos remotos a uno de los principales productos extraídos del agua del mar.

La sal.

La sal a la que se refería Plinio es un mineral que se forma por la unión de dos elementos químicos, el cloro y el sodio, y es la única roca que nos podemos comer directamente.

La mayor parte de la sal se encuentra disuelta en el agua de los mares y océanos, y para extraerla hemos desarrollado diferentes técnicas, la mayoría de ellas basadas en los procesos naturales de evaporación y cristalización como los que se llevan a cabo en las explotaciones salineras costeras donde, cada año, se extraen millones de toneladas.

Las salinas costeras son unos ecosistemas muy especiales. Su localización los convierte en zonas de acogida de aves de numerosas especies, muchas de las cuales establecen aquí sus colonias de cría, de alimentación o de invernada.

Las aguas que rodean a las salinas, que son las mismas de las que luego se extraerá la sal, albergan un ecosistema marino costero en el que aparecen representantes de una enorme cantidad de grupos de organismos. En ellas habitan, cianobacterias productoras de oxígeno que forman tapetes verdes que recubren los sedimentos poco profundos.

Una característica de estas cianobacterias es que sus filamentos están en constante movimiento y entre ellos deambulan los nemátodos, quizás los animales más abundantes en el planeta.

Algunas especies de moluscos ven también en estas aguas un lugar idóneo para que sus recién nacidas larvas dispongan de la tranquilidad necesaria para desarrollarse.

Los gusanos poliquetos son muy abundantes y colonizan tanto la superficie del sedimento como las conchas de otros animales mientras filtran el agua en busca de partículas orgánicas o diminutos microorganismos planctónicos, algo que también hacen constantemente urocordados como las ascidias.

Aquí es posible también encontrar diminutas y delicadas medusas microscópicas y una gran cantidad de crustáceos, tanto en sus estados adultos como en forma de larvas.

Todo ese ecosistema marino cambia radicalmente cuando el agua penetra en las salinas. Y los llamativos colores que muestran las lagunas en las que cristaliza la sal no son más que el reflejo de la singular biodiversidad que albergan. Una biodiversidad formada por una enorme cantidad de organismos microscópicos adaptados a vivir en unas condiciones de salinidad e insolación extremas.

Uno de esos organismos, quizás uno de los más característicos, es el alga Dunaliella salina, conocida precisamente como “alga de las salinas”.

Dunaliella salina es el organismo eucariota con mayor tolerancia a la sal y es esa tolerancia la que le permite habitar en estas aguas, cuyo contenido en sal puede alcanzar niveles extremos. Pero eso le provoca estrés, y cuando eso sucede, produce una sustancia con la que protegerse.

Esa sustancia protectora es el beta-caroteno, que es, precisamente, la que le proporciona su llamativo color rojo.

Dunaliella, además, produce grandes cantidades de otra sustancia, el glicerol que le sirve para regular la concentración de sal en el interior de la célula.

Pero la membrana de Dunaliella no es impermeable, y buena parte del glicerol escapa al medio, lo que constituye una excelente fuente de alimento, para la multitud de bacterias con las que convive.

Y es ahí donde aparece una relación especial entre los microorganismos que viven en las salinas y la producción de sal.

La abundancia de Dunaliella y de bacterias hace que el agua se caliente a mayor velocidad y que alcance temperaturas muy superiores a las del ambiente. Además, cada una de las bacterias puede actuar como núcleo para la formación de los cristales de sal de manera que el proceso se acelera.

Pero no todas las salinas se encuentran en la costa. Algunas también se localizan en el interior de los continentes, en zonas muy alejadas del mar.

Ilargi Martínez-Ballesteros, investigadora principal del griupo MikroIker, de la Universidad del País Vasco/Euskal Herriko Unibersitatea (UPV/EHU) nos habla de estas salinas y de sus recientes descubrimientos en ellas.

“Estamos en Salinas de Añana.

Esta salina es diferente quizás a las que podemos encontrar en otros lugares en la península, por ejemplo, ya que su característica singular es que la salmuera que se utiliza para la producción de sal sale por la presencia de un diapiro que está en este valle, en el Valle Salado de Añana.

Diferentes estudios han estado analizando a qué profundidad puede estar situado este diapiro, y no se sabe concretamente, pero parece puede tener más de 200 metros de profundidad. El agua que se filtra tiene contacto subterráneo con esa halita que hay en las profundidades que subterráneamente y la va disolviendo antes de salir a la superficie por diferentes manantiales que hay en el valle.

Una curiosidad de este valle, que además hemos visto que marca mucho la presencia de qué tipo de microorganismos halófilos hay en el agua de la salmuera en esta salina, es que a pocos metros de distancia hay diferentes manantiales con diferente salinidad.

Por ejemplo, hay dos manantiales, uno se llama El Pico y otro El Pico Dulce, que están a escasos metros de distancia, y los taxones, de los microorganismos que hemos hallado allí, no tienen nada que ver unos con los otros. Y esto es por la adaptación que han tenido y porque la cantidad de sal que hay en los diferentes manantiales, en la salmuera, es muy distinta.

En el Pico Dulce estamos hablando de un agua salina, que tiene en torno a 20-30 gramos de sal por litro, y en El Pico se alcanzan los 230-240 gramos de sal por litro, es totalmente salado.

Esa gran diferencia es lo que hemos visto que marca principalmente la presencia de uno u otro tipo de halófilos en la salmuera.

Otra de las características que hemos ido descubriendo al estudiar la presencia de material genético, de ADN, en el agua mediante su extracción y secuenciación, es que hemos podido identificar poblaciones bacterianas y de arqueas que han sido descritas previamente, pero se nos han quedado muchas secuencias, mucho ADN sin poder identificar.

Y sí que, por el momento, hemos encontrado que hay una especie nueva que se ha caracterizado aquí, en Salinas de Añana, en la salmuera del principal manantial, que es el Manantial de Santa Engracia.

Quizás estén viviendo microorganismos que todavía no conozcamos y quizás lleguemos a conseguir aislarlos y observarlos en el laboratorio.

Por otro lado, el estudio de los halófilos también es interesante porque se ha descubierto que, gracias a las adaptaciones que han ido desarrollando a lo largo de su evolución para poder sobrevivir en esas condiciones extremas de salinidad, producen diferentes metabolitos, productos, que pueden ser interesantes sus utilidades biotecnológicas.”

La nueva bacteria descubierta en las Salinas de Añana ha sido bautizada con el nombre de Altererythrobacter muriae, y entre sus características destaca su capacidad para vivir en un agua con una concentración de hasta 200 gramos de sal por litro, característica que la incluye en el grupo de los microorganismos considerados halotolerantes.

¿De qué se alimenta esta bacteria en la salmuera?

Altererythrobacter muriae, no lleva a cabo la fotosíntesis, no tiene clorofila, se alimenta de la materia orgánica que hay en las aguas en las que habita, por lo que se considera un organismo heteroorganotrófico.

Los científicos han podido comprobar que Altererythrobacter muriae produce unos pigmentos llamados carotenoides.

¿Qué función desempeñan estos pigmentos?

La principal función de este pigmento es el de actuar como un antioxidante, evitando los daños que el exceso de oxígeno pudiera causar a la bacteria.

Muchos de los microorganismos que habitan en las salinas de interior están considerados extremófilos, puesto que se han adaptado a vivir en condiciones ambientales extremas. En este caso en unas condiciones extremas de salinidad y, a menudo, también de insolación. Pero no todos son extremófilos. Otros, como Halomonas, una bacteria frecuente en estos entornos, no es extremófila sino halotolerante, es decir, que es capaz de soportar la salinidad propia de estas aguas aunque no es exclusiva de ellas.

Pero… ¿Por qué son saladas estas aguas de interior?  ¿Cómo ha llegado la sal hasta estas zonas?

Las gruesas capas de sal que quedaron al desaparecer mares antiguos se transformaron en una roca llamada halita, que es la que da cuerpo a lo que ahora conocemos con el nombre de domos o diapiros salinos.

El agua que circula por los acuíferos subterráneos atraviesa el diapiro y lo va disolviendo antes de salir al exterior con una elevada concentración de sal. Esa elevada concentración, unida al incremento de temperatura provocado por la insolación, hace que las sales comiencen a cristalizar.

Además del cloruro sódico o sal común, que es el principal componente de la halita, la roca que forma el diápiro, el agua también disuelve otros compuestos a su paso. Unos de los más frecuentes son sales de elementos como el calcio y el magnesio, generalmente en forma de carbonatos y sulfatos.

En este enlace podéis ver la belleza de los cristales de la Sal de Añana en formación: https://www.youtube.com/watch?v=8wiI2X-J-vM

Además de las salinas asociadas a los diápiros, en el interior de los continentes aparece un tipo especial de ecosistemas salinos. Se trata de lagunas que se localizan en terrenos áridos, en zonas en las que las precipitaciones son muy irregulares y generalmente escasas. A estos humedales se les conoce como “las saladas”.

Las saladas son lo que los científicos llaman lagunas endorreicas. Eso quiere decir que son lagunas que se forman en depresiones del terreno debido a que es allí donde se concentra el agua de lluvia. Un agua que disuelve las sales que conforman las rocas del terreno que rodea la laguna antes de acumularse en la cubeta, de la que únicamente sale por la evaporación provocada por el sol.

Es en el interior de esas aguas saladas donde encuentra su hábitat idóneo la Artemia salina, uno de los animales más resistentes a las altas concentraciones de sal. Se trata de un crustáceo cuya morfología parece no haber cambiado casi nada desde el período Triásico, y eso quiere decir que está extraordinariamente bien adaptado a esas singulares y extremas condiciones ambientales. Durante los períodos en los que las cubetas permanecen cubiertas por el agua, las artemias adultas se alimentan de las densas poblaciones de microalgas y se reproducen a gran velocidad, muchas veces sin intervención de los machos, mediante una estrategia que recibe el nombre de partenogénesis.

Pero ¿cómo sobreviven a las largas temporadas de sequía?

El secreto de su supervivencia es una estrategia que recibe el nombre de criptobiosis, algo así como “vida escondida”. Cuando el agua desaparece completamente, los huevos producidos por la artemia quedan atrapados por la sal y expuestos al aire y al sol, situación en la que pueden permanecer durante mucho tiempo. En ocasiones durante más de diez años.

Son huevos de resistencia, que permanecen inactivos hasta que el agua de lluvia vuelve a rellenar la laguna. Es entonces cuando esos huevos se rehidratan, “despiertan” y eclosionan dejando salir al exterior a las nuevas larvas que habían permanecido dormidas en su interior en forma de embrión. De esta manera, esas nuevas generaciones restablecen las poblaciones de artemia en un aparente ciclo sin fin.

Un ciclo natural que se ha mantenido en funcionamiento desde hace más de 200 millones de años y que está regulado por el agua y por la concentración de uno de los elementos clave en estos ecosistemas, la sal.

Puedes ver el episodio “La sal de la vida” (25 minutos. V.O. en Español. Subtitulado en Inglés y Portugués) de nuestra serie “Planeta microbio” en este enlace:

https://caixaforumplus.org/v/la-patrulla-ambiental

La entrada La sal de la vida se publicó primero en Science into Images.

IN SEARCH OF IMMORTALITY

The search for immortality has been one of the obsessions of human beings since they became aware of their own death.

Leaving aside any other approach, and looking at it from a purely biological point of view, we can consider any living being as a physical system. And, consequently, subject to the laws of the physical world.

One of the most important laws in this field are the laws or principles of thermodynamics.

The first, perhaps the best known, states that energy is neither created nor destroyed, it only transforms. And the second, expressed colloquially, says that any physical system has a tendency to spontaneously become disordered.

In principle, these laws are applicable to any closed system, that is, isolated from the environment.

However, living beings are not closed systems. We maintain a permanent exchange of matter and energy with our environment. And thanks to this exchange we can escape the thermodynamic yoke and maintain our “order”, at least for a certain time.

Maintaining this order is what we call homeostasis, and it is what allows us to stay alive in a constant state of dynamic equilibrium.

But what happens when we are unable to maintain this balance?

Well, we become disordered and, finally, we die.

Why do we become disordered? Why do we lose the ability to maintain homeostasis?

All living beings today store genetic information in the form of DNA.

Eukaryotic organisms, like us, have our DNA protected within the nucleus of our cells and organized into small packages. Each of these packages is what is called a chromosome.

Studies on the aging and death of our cells have shown that it is precisely in this way of organizing our DNA where the problem lies.

Chromosomes are made up of linear DNA molecules, and at the ends of each of them there is a portion of DNA called a telomere. This portion is what prevents the different chromosomes from linking together at the ends during cell division. But every time a cell divides, the telomeres of its chromosomes get shorter. Eventually, after a certain number of divisions, the telomeres are so short that the DNA in the chromosomes cannot be duplicated properly, the cell cannot divide, and it dies.

Final stage of binary division or bipartition of a ciliated protozoan.

This process of cell death is called apoptosis. And the number of times a cell can divide before dying is called the Hayflick limit, and it varies from organism to organism.

For most of our cells, this limit is around 60 divisions. However, we have cells that can overcome it.

These cells are germ cells -which give rise to ovules and sperm- and stem cells, which can divide indefinitely.

Does this mean that these cells are immortal?

Apparently so. Sometimes, other cells in our body are able to avoid the Hayflick limit and begin to divide uncontrollably. When this happens, we face a serious problem: cancer.

Human cancer cells in different mitosis phase.

As explained by Professor Pedro Luis Fernández, Head of the Pathological Anatomy Service at the Germans Trias i Pujol Hospital, “the term cancer is a Latin word meaning crab, and it is how ancient Greek and Roman physicians called lesions that were destructive to the body and that usually had the shape of this animal.

The origin of cancer is found within the body’s own cells. Some of these cells can undergo changes in their normal behavior and behave in an aggressive manner. These are what we call cancer cells.

In reality, cancer is not a disease but a series of diseases that have some characteristics in common. They can appear in any cell of the body and in any tissue, but they can eventually behave in such a way that they can end up killing the individual.

Large cancerous tumor in a patient’s lung.

The common characteristics of cancer cells are multiple, but three stand out:

The first is that they can evade programmed cell death, what we call apoptosis, and therefore they can live much longer than normal. The second is that they can multiply much more quickly and many times more than normal, exceeding what we call the Hayflick limit. In addition, if we put these cells in culture and provide them with the appropriate nutrients, we can say that they become immortalized.

And finally, a third characteristic would be that, as they are cells that arise from the organism itself, they are able to evade the systems that recognize them as foreign and, therefore, evade that death produced by the organism itself, among which the evasion of the immune surveillance system stands out.

We can compare this cancerous process, using the famous Ridley Scott film, to an alien. An alien that emerges, grows, feeds and can eventually kill the organism. But it is a selfish entity, a stupid and suicidal entity, because it will eventually kill its source of subsistence, since, unlike what happened with the entity in the film, it cannot pass from one individual to another.

Or can it?

There is what specialists call hereditary cancer, but, in reality, it does not pass from one person to another at the time of reproduction, what it means is that the reproductive cells, the eggs or the sperm, can harbor genetic alterations that can be transmitted to the offspring without necessarily meaning that they will suffer from cancer. It may simply happen that, throughout an individual’s life, and due to external influences, such as carcinogens, other genetic alterations occur that end up developing a malignant disease, cancer, which usually occurs in adults.

The appearance of cancer causes an imbalance in the organisms that suffer from it, a loss of their homeostasis, of their ability to self-regulate and maintain their normal functioning. However, the apparent “immortality” of cancer cells gives us some clues to find possible ways to achieve the long-awaited immortality.”

Since its appearance on the planet, life has diversified enormously. Biological evolution, always in response to the evolution of the planet itself, has given rise to the appearance of numerous life forms. And each of them has developed a unique, singular way of maintaining its homeostasis.

Is it possible that any of them has managed to avoid disorder and, consequently, death?

The answer to that question will surely have to be sought in life forms much older and simpler than us.

Protozoa and microalgae, all eukaryotic organisms formed by a single cell, have inhabited the planet since long before animals appeared. So we could think that they have had much more time to look for a solution to the problem.

Group of ciliated protozoa of the genus Paramecium.

Have they found it? Have they managed to be immortal?

Organisms as seemingly simple as protozoa are capable of dividing more than 200 times, many more times than our normal cells. They also have their DNA organized into chromosomes like ours, and those chromosomes also have telomeres at their ends.

How do they prevent those telomeres from shortening?

The secret lies in an enzyme, a molecule that rebuilds telomeres after each division. That apparently “magic” molecule is called telomerase.

That same enzyme appears in our germ cells, our stem cells and, unfortunately, also in cancer cells.

However, it has been proven that protozoa such as paramecia also suffer senescence, that is, they also age and end up losing their reproductive capacity. Therefore, it seems that these organisms have not achieved immortality either.

Sequence of membrane destruction and subsequent death of two ciliated protozoans. Above: Paramecium bursaria. Below: Paramecium caudatum.

All the organisms we have talked about so far are made up (we too) of eukaryotic cells, cells with a nucleus and with DNA organized in the form of linear chromosomes. But what about bacteria and archaea?

Bacteria and archaea are prokaryotic organisms, they do not have a defined cell nucleus. And their genetic material, their DNA, is not packaged in linear chromosomes, but forms a single circular chromosome.

Being circular, the bacterial chromosome has no ends and, therefore, no telomeres, so it does not suffer shortening during the cycles of division and reproduction.

We might think, as has been thought for a long time, that, due to this characteristic, bacteria and archaea are immortal. However, recent studies carried out with one of the best-known bacteria, the famous Escherichia coli, have shown that this is not entirely true. Some of the cells resulting from the division of this bacteria, from its reproduction by bipartition, show a lower reproductive capacity than that of their sisters, that is, they age and, finally, their line of descent ends up disappearing.

It seems, then, that neither reproduction by bipartition, nor the possession of a circular chromosome, without telomeres, ensures immortality.

Is there any other strategy? Is there any other possibility of being immortal?

Some groups of bacteria, including those that make up the genera Bacillus and Clostridium, have the ability to form endospores as a resistance strategy when environmental conditions are not suitable.

We could consider these bacterial endospores as tiny “time capsules” inside which the bacteria remains in a “dormant” state. When environmental conditions become favorable again, the spore opens, germinates, and the bacteria inside it reappears.

Bacterial population with some sporulated cells.

The question then is how long can the bacteria remain inside the spore in this “dormant” state?

In 1995, California researchers published the “resurrection” of a bacteria, or rather, the germination of one of these bacterial spores, found inside the intestine of a bee preserved in amber for more than 25 million years. (Cano, R. J. and Borucki, M. K.: 1995, Revival and Identification of Bacterial Spores in 25–40 Million-Year-Old Dominican Amber, Science 268, 1060–1064.)

But there is more.

Five years later, in 2000, another American group of researchers published a study in which they claimed to have “resurrected” another bacteria. This time the spore was contained in a salt crystal extracted from more than 500 m deep in the Salado geological formation in New Mexico. It was 250 million years old. (Vreeland, R. H., W. D. Rosenzweig and D. W. Powers. 2000. Isolation of a 250 million-year-old halotolerant bacterium from a primary salt crystal. Nature. 407 (6806): 897-900.)

Is this immortality?

You can watch the episode “In search of immortality” (25 minutes. O.V. in Spanish. Subtitled in English and Portuguese) of our series “Planeta microbio” through this link:

https://caixaforumplus.org/v/en-busca-de-la-inmortalidad

La entrada IN SEARCH OF IMMORTALITY se publicó primero en Science into Images.

Sometimes, the scientific knowledge of the time has provided a clear and reasoned explanation for these phenomena, but in many other cases, it has not.

When we cannot explain certain events with the knowledge available to us, we are left perplexed and astonished. It is in these moments that we turn to supernatural explanations, resorting to magic or religion.

When we lean on religious beliefs, we assume that these strange and seemingly inexplicable phenomena are the result of the intervention of beings with capabilities far beyond our own—beings we generally call “gods.”

And at that moment, the phenomenon transforms into a “miracle.”

However, the advancement of science over the centuries has allowed us to verify that many of these miracles—many of the phenomena once considered supernatural or unfathomable—actually have scientific, natural explanations.

And in many cases, the ultimate culprits behind these phenomena have been microbes.

One of the most representative “miraculous” microbes is the bacterium known as Serratia marcescens.

Serratia is a microbe capable of staining surfaces where its colonies grow with a blood-red color—such as bread or even religious statues.

It is precisely its proliferation on these two elements that led to the belief that the liquid emanating from them was real blood.

It is not surprising that, due to these characteristics, scientists have nicknamed this microorganism the “miraculous bacterium” and have named the blood-red pigment it produces “prodigiosin.”

Serratia, whose typically bacterial circular chromosome contains only about 4,800 genes, is a rod-shaped bacterium—what microbiologists call a bacillus. Like most bacteria, it is tiny, measuring no more than two-thousandths of a millimeter in length.

We can find it almost everywhere: in the soil, in water, on plants, on animals… It is, in essence, a cosmopolitan bacterium.

As is often the case with most bacteria, we only become aware of its existence when its uncontrolled growth causes health problems for us or the ecosystems in which we live.

When its growth within our bodies becomes unregulated, Serratia can cause conjunctivitis, infections in wounds, kidneys, and urinary tracts, respiratory infections, meningitis, and endocarditis. In fact, some historians claim that this bacterium has caused more deaths than any other bacillus in human history.

Today, Serratia is frequently associated with various serious hospital-acquired infections, particularly dangerous for immunocompromised patients. For this reason, it is intensively studied in laboratories and hospitals.

But not everything about it is negative.

As a result of these studies, researchers have discovered that Serratia’s pigment, prodigiosin, induces apoptosis in cancer cells—that is, it triggers their natural death. It also acts as an immunosuppressive drug in organ transplant surgeries, preventing rejection.

Moreover, it has been found that this pigment is highly effective against one of the life stages of the spirochete Borrelia burgdorferi, the bacterium that causes Lyme disease and is transmitted by ticks.

Nature itself, the evolution of life on our planet, offers us countless examples of phenomena that could be considered “miracles.”

And once again, bacteria play a starring role.

One such example is the drastic transformation of our atmosphere approximately 2.4 billion years ago.

Until then, Earth’s atmosphere was dominated by gases such as hydrogen, water vapor, carbon monoxide, carbon dioxide, methane, hydrogen sulfide, and various nitrogen compounds—remnants of the planet’s formation and the numerous celestial impacts on its surface.

This primitive atmosphere contained almost no free oxygen—it was an anaerobic atmosphere.

During this extended period of our planet’s evolution, life was entirely prokaryotic, meaning all living beings were bacteria and archaea.

For millions of years, some of these microorganisms were able to harness energy from sunlight to perform photosynthesis.

However, the type of photosynthesis they carried out—and still do, as many of these organisms continue to share the planet with us—did not release oxygen. This is what we call anoxygenic photosynthesis.

These microorganisms did not break down water to obtain energy but instead used a compound similar in structure to water: hydrogen sulfide, the substance responsible for the foul smell of “rotten eggs.” In those early days of Earth, volcanic activity was the main source of this compound.

As a result, instead of releasing oxygen, these microorganisms released sulfur.

When hydrogen sulfide was broken down, two elements appeared: hydrogen, which the bacteria used for their metabolism, and sulfur, which was often deposited as elemental sulfur granules either in the environment or within bacterial cells.

Then, about 3 billion years ago, a special type of bacteria—the cyanobacteria—figured out how to use a much more abundant compound thanhydrogen sulfide: water.

This new metabolic innovation, known as oxygenic photosynthesis, was fundamental to the evolution of life on Earth. Instead of releasing sulfur, it led to the release of oxygen—a highly reactive and initially toxic gas.

The oxygen released accumulated in the oceans, where it reacted with dissolved chemical elements, removing it from the environment.

One of these elements was iron, which was extraordinarily abundant due to the planet’s formation processes.

Oxygen reacted with iron to form iron oxide, which settled into ocean sediments. As a result, very little of the oxygen produced by bacterial photosynthesis escaped into the atmosphere.

A clear record of this process is found in extraordinary geological formations known as banded iron formations, which can be observed in many regions of the planet.

Then, about 2.4 billion years ago, the amount of dissolved iron in ocean water was no longer sufficient to capture all the oxygen produced by bacterial photosynthesis. Oxygen began to accumulate in the atmosphere in large quantities, rising from about 1% to the 21% we have today.

This event is known as the Great Oxidation Event.

The organisms that had lived on Earth until then were not adapted to an oxygen-rich atmosphere, which was highly toxic to them. This led to a massive extinction.

Almost all life on the planet disappeared, and new forms of life began to evolve—ones capable of developing strategies to protect themselves from the dangerous gas.

The majority of life on Earth transitioned from anaerobic to aerobic, as it is today.

And there’s more.

Around 2 billion years ago, some of these new, more complex life forms—capable of surviving in an oxygenated environment because they had incorporated oxygen-respiring bacteria that would later become mitochondria—engulfed a small cyanobacterium. Instead of digesting it, they allowed it to live inside them.

Over time, this cyanobacterium became a chloroplast, the organelle most characteristic of all plant cells.

As a result, the new cell, which could already survive in an oxygenated environment, also became capable of harnessing solar energy for its metabolism—meaning it could now perform photosynthesis.

What was the outcome of this extraordinary union, this marvelous bacterial symbiosis?

The result was the birth of the first plant cell—the type of cell that forms all the plants we see today, from tiny unicellular algae like diatoms to giant trees that breathe life into our forests.

Today, various studies show that free-living cyanobacteria are responsible for between 50% and 70% of the oxygen released into the atmosphere from the planet’s surface. However, since they became chloroplasts and now form part of all plant cells, cyanobacteria are actually responsible for nearly 100% of the oxygen in our atmosphere.

Could there be more “miraculous” microbes than these?

La entrada Microbios milagrosos se publicó primero en Science into Images.

Surely, just by seeing the platform’s name, you’ve already guessed that Fundación La Caixa is behind this wonderful initiative—a bold and innovative project that aims to make cultural content accessible to anyone who wants it. And the best part? It’s completely free! (I’ll tell you more about that later).

The presentation was spectacular, featuring a wonderful musical performance by Oscar D’aniello (Delafé).

Cayetana Guillén Cuervo, current president of the Academy of Performing Arts, actress, and television presenter, among many other things, served as the master of ceremonies with her characteristic grace and elegance. One by one, the different “protagonists”—people who have participated in some of the platform’s available content—took the stage at her invitation.

Seated on the stage’s “chester” (sofa) were Elisa Durán (Deputy General Director of Fundación La Caixa), Víctor García de Gomar (Artistic Director of Gran Teatre del Liceu), Guillermo Solana (Artistic Director of the Thyssen-Bornemisza National Museum), Leticia Dolera (actress, director, and audiovisual producer) and María Arnal (artist and composer), who also delighted us all with a beautiful rendition of El Cant de la Sibil·la.

As you can see, all these figures fit within the traditional concept of “culture”—painting, theater, cinema, music…

But to fulfill the platform’s broader vision, as expressed at the beginning by Elisa Durán, something was missing: science.

That’s why, at Cayetana’s invitation, two much lesser-known figures took the stage: Bartolomé Luque (Doctor in Physical Sciences and professor at the Polytechnic University of Madrid) and myself (labeled as a biologist, science communicator, and photographer).

There we were, Bartolo (only my mother calls him Bartolomé, sic) and I, sitting on the famous “chester,” probably sparking the curiosity of the audience, who likely knew little about us. And that’s precisely what we talked about—the curiosity that drives knowledge and the false distinction between science and culture, a misconception that CaixaForum+ is fortunately working to dismantle. We also discussed the importance of scientific rigor in communication, the pandemic, Einstein, the first step on the Moon, the Fourier transform, algebra, numbers and letters, the invisible, the idea of being “a science person” or “a humanities person,” religion and science, flat-earthers and anti-vaxxers… basically, if they had let us, we would have talked about The Thirty Pieces of Silver too! Some of Bartolo’s examples even got the audience laughing (Science and humor? Apparently, it’s possible—even while taking science completely seriously!). In the end, thanks to Bartolo’s spontaneity and my txapela (Basque beret), we earned the (hopefully affectionate) nickname “the odd couple.”

A key role in shaping this “odd couple” was played by Mireia Gubern, Marta Morales, and Ignasi Miró from Fundación La Caixa’s Corporate Directorate of Culture and Science, with whom I have a wonderful working relationship.

I encourage everyone to subscribe to the platform, either via the web version (https://caixaforumplus.org/) or through the tablet and mobile app, available on Google Play and the App Store.

There, among more than 900 productions and 600 hours of content (a number that will continue to grow), you’ll find our series Habitantes del Micromundo (Inhabitants of the Microworld), where you can learn more about the “invisible” beings I mentioned earlier.

And speaking of the invisible, I’d like to express my heartfelt gratitude to the amazing team working behind the scenes at the event—sound technicians, makeup artists, stage coordinators—for their kindness and support at all times. Thank you all so much!

Photos are taken from various media sources.

La entrada CaixaForum+: A Window to Culture se publicó primero en Science into Images.