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Extreme thermophilic bacteria thrive at any temperature above 40/50°C. Thermotoga Maritima seems to be the bacteria that can survive at the highest temperature up to 90°C (reference 1, table 2). I wonder if there is a more exhaustive list of extreme thermophilic bacteria and if there is a known bacteria that can survive at higher temperatures than Thermotoga Maritima.
References: Ref.1 Front. Microbiol., 05 November 2015 | https://doi.org/10.3389/fmicb.2015.01209 Extremely thermophilic microorganisms as metabolic engineering platforms for production of fuels and industrial chemicals
Geogemma barossii, initially designated Strain 121, can survive and reproduce at 121°C, with an optimal growth temperature of 103°C. It's not a bacterium though, but a member of the Archaea domain.
Extremophiles and Extreme Environments
Over the last decades, scientists have been intrigued by the fascinating organisms that inhabit extreme environments. Such organisms, known as extremophiles, thrive in habitats which for other terrestrial life-forms are intolerably hostile or even lethal. They thrive in extreme hot niches, ice, and salt solutions, as well as acid and alkaline conditions some may grow in toxic waste, organic solvents, heavy metals, or in several other habitats that were previously considered inhospitable for life. Extremophiles have been found depths of 6.7 km inside the Earth’s crust, more than 10 km deep inside the ocean𠅊t pressures of up to 110 MPa from extreme acid (pH 0) to extreme basic conditions (pH 12.8) and from hydrothermal vents at 122 ଌ to frozen sea water, at ଌ. For every extreme environmental condition investigated, a variety of organisms have shown that they not only can tolerate these conditions, but that they also often require those conditions for survival.
They are classified according to the conditions in which they grow: As thermophiles and hyperthermophiles (organisms growing at high or very high temperatures, respectively), psychrophiles (organisms that grow best at low temperatures), acidophiles and alkaliphiles (organisms optimally adapted to acidic or basic pH values, respectively), barophiles (organisms that grow best under pressure), and halophiles (organisms that require NaCl for growth). In addition, these organisms are normally polyextremophiles, being adapted to live in habitats where various physicochemical parameters reach extreme values. For example, many hot springs are acid or alkaline at the same time, and usually rich in metal content the deep ocean is generally cold, oligotrophic (very low nutrient content), and exposed to high pressure and several hypersaline lakes are very alkaline.
Extremophiles may be divided into two broad categories: extremophilic organisms which require one or more extreme conditions in order to grow, and extremotolerant organisms which can tolerate extreme values of one or more physicochemical parameters though growing optimally at “normal” conditions.
Extremophiles include members of all three domains of life, i.e., bacteria, archaea, and eukarya. Most extremophiles are microorganisms (and a high proportion of these are archaea), but this group also includes eukaryotes such as protists (e.g., algae, fungi and protozoa) and multicellular organisms.
Archaea is the main group to thrive in extreme environments. Although members of this group are generally less versatile than bacteria and eukaryotes, they are generally quite skilled in adapting to different extreme conditions, holding frequently extremophily records. Some archaea are among the most hyperthermophilic, acidophilic, alkaliphilic, and halophilic microorganisms known. For example, the archaeal Methanopyrus kandleri strain 116 grows at 122 ଌ (252 ଏ, the highest recorded temperature), while the genus Picrophilus (e.g., Picrophilus torridus) include the most acidophilic organisms currently known, with the ability to grow at a pH of 0.06.
Among bacteria, the best adapted group to various extreme conditions is the cyanobacteria. They often form microbial mats with other bacteria, from Antarctic ice to continental hot springs. Cyanobacteria can also develop in hypersaline and alkaline lakes, support high metal concentrations and tolerate xerophilic conditions (i.e., low availability of water), forming endolithic communities in desertic regions. However, cyanobacteria are rarely found in acidic environments at pH values lower than 5𠄶.
Among eukaryotes, fungi (alone or in symbiosis with cyanobacteria or algae forming lichens) are the most versatile and ecologically successful phylogenetic lineage. With the exception of hyperthermophily, they adapt well to extreme environments. Fungi live in acidic and metal-enriched waters from mining regions, alkaline conditions, hot and cold deserts, the deep ocean and in hypersaline regions such as the Dead Sea. Nevertheless, in terms of high resistance to extreme conditions, one of the most impressive eukaryotic polyextremophiles is the tardigrade, a microscopic invertebrate. Tardigrades can go into a hibernation mode, called the tun state, whereby it can survive temperatures from ଌ (1 ଌ above absolute zero!) to 151 ଌ, vacuum conditions (imposing extreme dehydration), pressure of 6,000 atm as well as exposure to X-rays and gamma-rays. Furthermore, even active tardigrades show tolerance to some extreme environments such as extreme low temperature and high doses of radiation.
In general, the phylogenetic diversity of extremophiles is high and very complex to study. Some orders or genera contain only extremophiles, whereas other orders or genera contain both extremophiles and non-extremophiles. Interestingly, extremophiles adapted to the same extreme condition may be broadly dispersed in the phylogenetic tree of life. This is the case for different psychrophiles or barophiles, for which members may be found dispersed in the three domains of life. There are also groups of organisms belonging to the same phylogenetic family that have adapted to very diverse extreme or moderately extreme conditions.
Over the last few decades, the fast development of molecular biology techniques has led to significant advances in the field, allowing us to investigate intriguing questions on the nature of extremophiles with unprecedented precision. In particular, new high-throughput DNA sequencing technologies have revolutionized how we explore extreme microbiology, revealing microbial ecosystems with unexpectedly high levels of diversity and complexity. Nevertheless, a thorough knowledge of the physiology of organisms in culture is essential to complement genomic or transcriptomic studies and cannot be replaced by any other approach. Consequently, the combination of improved traditional methods of isolation/cultivation and modern culture-independent techniques may be considered the best approach towards a better understanding of how microorganisms survive and function in such extreme environments.
Based on such technological advances, the study of extremophiles has provided, over the last few years, ground-breaking discoveries that challenge the paradigms of modern biology and make us rethink intriguing questions such as “what is life?”, “what are the limits of life?”, and “what are the fundamental features of life?”. These findings have made the study of life in extreme environments one of the most exciting areas of research, and can tell us much about the fundaments of life.
The mechanisms by which different organisms adapt to extreme environments provide a unique perspective on the fundamental characteristics of biological processes, such as the biochemical limits to macromolecular stability and the genetic instructions for constructing macromolecules that stabilize in one or more extreme conditions. These organisms present a wide and versatile metabolic diversity coupled with extraordinary physiological capacities to colonize extreme environments. In addition to the familiar metabolic pathway of photosynthesis, extremophiles possess metabolisms based upon methane, sulfur, and even iron.
Although the molecular strategies employed for survival in such environments are still not fully clarified, it is known that these organisms have adapted biomolecules and peculiar biochemical pathways which are of great interest for biotechnological purposes. Their stability and activity at extreme conditions make them useful alternatives to labile mesophilic molecules. This is particularly true for their enzymes, which remain catalytically active under extremes of temperature, salinity, pH, and solvent conditions. Interestingly, some of these enzymes display polyextremophilicity (i.e., stability and activity in more than one extreme condition) that make their wide use in industrial biotechnology possible.
From an evolutionary and phylogenetic perspective, an important achievement that has emerged from studies involving extremophiles is that some of these organisms form a cluster on the base of the tree of life. Many extremophiles, in particular the hyperthermophiles, lie close to the “universal ancestor” of all organisms on Earth. For this reason, extremophiles are critical for evolutionary studies related to the origins of life. It is also important to point out that the third domain of life, the archaea, was discovered partly due to the first studies on extremophiles, with profound consequences for evolutionary biology.
Furthermore, the study of extreme environments has become a key area of research for astrobiology. Understanding the biology of extremophiles and their ecosystems permits developing hypotheses regarding the conditions required for the origin and evolution of life elsewhere in the universe. Consequently, extremophiles may be considered as model organisms when exploring the existence of extraterrestrial life in planets and moons of the Solar System and beyond. For example, the microorganisms discovered in ice cores recovered from the depth of the Lake Vostok and other perennially subglacial lakes from Antarctica may serve as models for the search of life in the Jupiter’s moon Europa. Microbial ecosystems found in extreme environments like the Atacama Desert, the Antarctic Dry Valleys and the Rio Tinto may be analogous to potential life forms adapted to Martian conditions. Likewise, hyperthermophilic microorganisms present in hot springs, hydrothermal vents and other sites heated by volcanic activity in terrestrial or marine areas may resemble potential life forms existing in other extraterrestrial environments. Recently, the introduction of novel techniques such as Raman spectroscopy into the search of life signs using extremophilic organisms as models has open further perspectives that might be very useful in astrobiology.
With these groundbreaking discoveries and recent advances in the world of exthemophiles, which have profound implications for different branches of life sciences, our knowledge about the biosphere has grown and the putative boundaries of life have expanded. However, despite the latest advances we are just at the beginning of exploring and characterizing the world of extremophiles. This special issue discusses several aspects of these fascinating organisms, exploring their habitats, biodiversity, ecology, evolution, genetics, biochemistry, and biotechnological applications in a collection of exciting reviews and original articles written by leading experts and research groups in the field. I would like to thank the authors and co-authors for submitting such interesting contributions. I also thank the Editorial Office and numerous reviewers for their valuable assistance in reviewing the manuscripts.
Which is the most extreme thermophilic bacteria known? - Biology
"Extremophile" is a term that refers to bacteria that are able to grow and sustain in extremely harsh environments when compared to the environments that are termed as favourable for the growth of bacteria. Organisms have been discovered in the volcanic outlets, in the cold of Antarctic and Arctic regions, on the bottom of oceans, in deep sea hydrothermal vents, in very dry environments, inorganic environments such as acidic, alkaline and salt which are detrimental to most life forms, in lethal ionizing radiation environments and also in rocks extending far down inside the earth. It was not until the 1970's that these organisms were recognised. Thermophiles were the first extremophiles to be discovered. The domain archaea consists of extremophiles and many eukaryotes are also known to live in such harsh environments. There is also prosperity of organisms and unique living organisms, known as tube worms, growing around deep sea hydrothermal vents. These organisms are sustained without receiving energy from the sun. The discovery of extremophiles has increased speculation of chances for bacterial life on planets such as Mars, Europa (moon of Jupiter) and other stellar bodies.
The unparallel enzymes "extremoenzymes" used by the extremophiles to carry out their biochemical processes in harsh environments are useful in biotechnological processes. The property of capability of surviving under hard conditions by the enzymes, such as ability to function at very high pressure and temperature are major tools in biotechnolological research. Popular example is the so called taq polymerase enzyme isolated from the extremophile Thermus aquaticus is an essential part in PCR (polymerase chain reaction) technique that has brought radical change in biotechnology. And the most extraordinary microbe Deinococcus radiodurans is able to withstand high levels of lethal ionizing radiation.
Extremophile is a union of the suffix 'phile'-meaning 'lover of' and a prefix particular to their environments. Some categories of extremophiles include:
&bull Acidophiles - organisms living in acidic environments. They normally are found surrounding geothermal vents which are active and the pH of the same are below 5 which is acidic. They also occur in contaminated places where mining or industrial activity has left acidic wastes.
&bull Alkaliphiles - organisms living in typically alkali environments where the soil is abundant with carbonate having a pH of above nine. The enzymes that function at such high alkaline state are explored in laundry by detergent manufacturers which operate at alkaline pH.
&bull Halophiles - salt-loving organisms or bacteria such as Halobactreium salinarum grow in environments where the Na concentration is very high such as in Dead Sea or Great Salt Lake.
&bull Thermophiles - organisms living in high temperature of 80oC (177oF) such as in hot springs of Yellowstone National Park, Black Smokers etc.
&bull Psychrophiles - these organisms are very low temperature dwelling organisms. Example, Polaromonas vacuolata has maximum growth at 4oC (39.2oF) which just above the ice point of the water. Due to this unique ability to survive, these bacteria are being applied in enzymatic processes that operate near freezing temperature and also industrially being applied in the cold cycle washing machines.
&bull Endoliths - organisms living inside the rocks and carry out anaerobic form of respiration.
&bull Xerophile -organisms capable of growing at very low water activity such as in tough deserts.
&bull Barophiles (piezophile) - organisms living in high hydrostatic pressure such as in very depth of terrestrial surfaces and oceanic trenches.
&bull Methanogens - organisms that produce methane from the reaction between hydrogen and carbondioxide.
&bull Metallotolarent - organisms which are capable of withstanding high levels of dissolved toxic metals in solution such as cadmium, arsenic etc
&bull Oligotroph - organisms capable of growing in nutrition restrained conditions.
&bull Radioresistant - organisms capable of surviving high levels of toxic and fatal ionizing radiations.
These awesome organisms don't just survive in these harsh brutal environments they develop, propagate and do best in extreme environments than in any other place. They show characteristics in between bacteria and eukaryotes. The study of the extreme environments and the organisms that live in those environments has a tremendous merit for us. Exploring extreme environments are necessary to understanding biology, it is also essential in search for traces of life on other planets. The study of extremophiles helps us to know evolution that is the process of evolution and to study the primitive earth because early planet was an extreme habitat. Extremophile study is also important part of astrobiology and their enzymes find numerous commercial applications.
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Unconventional lateral gene transfer in extreme thermophilic bacteria
Conjugation and natural competence are two major mechanisms that explain the acquisition of foreign genes throughout bacterial evolution. In recent decades, several studies in model organisms have revealed in great detail the steps involved in such processes. The findings support the idea that the major basis of these mechanisms is essentially similar in all bacteria. However, recent work has pinpointed the existence of new, evolutionarily different processes underlying lateral gene transfer. In Thermus thermophilus HB27, at least 16 proteins are required for the activity of one of the most efficient natural competence systems known so far. Many of those proteins have no similarities to proteins involved in natural competence in other well-known models. This unusual competence system is conserved, in association with the chromosome, in all other Thermus spp. genomes so far available, it being functional even in strains from isolated environments, such as deep mines. Conjugation is also possible among Thermus spp. Homologues to proteins implicated in conjugation in model bacteria are encoded in the genome of a recently sequenced strain of Thermus thermophilus and shared by other members of the genus. Nevertheless, processive DNA transfer in the absence of a functional natural competence system in strains in which no conjugation homologous genes can be found hints at the existence of an additional and unconventional conjugation mechanism in these bacteria.
Base Biases of Thermophilic Genomes
Genomic structure in thermophiles is thought to be more stable than that of mesophiles. Although the contents of guanine (G) and cytosine (C) in the genome are important indicators of DNA stability, large-scale genomic comparisons between thermophiles and mesophiles have been conducted to evaluate the nucleic acid compositional differences. The GC content in some thermophiles is different from that of mesophiles, such as Thermus thermophilus ATCC 33923 with a GC content of 69.41% (38), Geobacillus kaustophilus with 52.1% (75), and Thermus sp. strain CCB_US3_UF1 with 68.6% (76). Muston et al., therefore, hypothesized that a high GC content contributes to the thermostability of the genome and is correlated with the OGT (57, 58). Additionally, tRNAs and rRNAs, the translational machinery of some thermophilic organisms, were reported to have high GC contents as well (5, 6, 70, 83). Some investigators, however, have argued that some microbes have different OGTs but share similar and even lower GC contents, such as Caldicellulosiruptor hydrothermalis containing only 35% GC with an OGT of 70°C (12). Therefore, the GC composition seems to be independent of thermophily, at least not universal to all thermophiles (6, 70, 82, 90). On the other hand, a significantly high AG content in mRNAs is observed as a selective response for survival among thermophiles. Compared with mesophilic species, thermophilic mRNAs exhibited an enrichment of purines and purine clusters with significantly high purine/pyrimidine ratios, especially biased toward those genes encoding central elements of transcriptional and translational machinery, such as ribosomal protein and histone-like protein genes (7, 63). The correlation of the purine content and OGT, however, lacks further confirmation (52). Therefore, it is certain that the base bias contributes to thermophily, but the correlation between the base bias and thermophily should be evaluated using more factors, such as the growth environment and the Gram-positive or -negative features of the bacteria.
The pattern of synonymous codon usage in protein-coding sequences is another important feature in evaluating the genomic structure of thermophilic species. The synonymous codon usage in thermophiles is different from that of mesophilic species, mainly in arginine and isoleucine codons in which thermophiles more frequently use the AGG, ATA, and AGA codons and avoid CGT and CGA (36, 49, 51, 74). The exhaustive genomic evaluation of nucleotide combinations suggests that A and G appear as nearest neighbors with a high frequency in thermophile genomes (90). Basak et al. postulated the bias usage of codons possibly resulted from the maintenance of codon-anticodon interaction energy at an intermediate strength so that the translation process could proceed smoothly (8). A recent study revealed that the synonymous codon usages are related directly with the OGT of the encoded enzyme activity (48). The differences in synonymous codon usage in thermophiles are thus believed to be important factors that are strongly linked with the selective pressure of the growth temperature.
Obviously, the base biases directly impact the variations of amino acid usages in proteins. The analyses of the proteins of thermophilic organisms suggest that the amino acid composition in the proteomes of thermophiles is distinguishable from that of mesophiles. Although debating some observations is generally accepted, such as an increase in the frequency of charged residues (Glu, Arg, and Lys), a decrease in the frequency of polar uncharged residues (Asn, Gln, Ser, and Thr), a decrease in the frequency of thermo-labile amino acids (His, Gln, and Thr), and an increase in the (Glu + Lys)/(Gln + His) ratio in thermophiles (27, 43, 74, 77). In addition, Zeldovich et al. claimed that the amino acid sequence IVYWREL might serve as a universal proteomic signature of thermophilic features for prokaryotic microorganisms (90). The special amino acid usage, therefore, is reasoned as a strategy for thermo-adaptation.
Yellowstone: Life, Literature, and the Persuit of Thermophiles
During one hot summer a little more than a century ago, the Great Fire of 1910 ripped through and burned over 3 million acres in Montana and Idaho, killing 86 people in its path. Mixed with humans’ natural aversion toward large fires, the Great Fire fueled the ideology that all forest fires in the West must be stopped. The foresters in the Department of Agriculture created a zero-tolerance policy to fires.
The Smokey the Bear ethic was born!
This total intolerance of fires, however, had its cost. In the summer of 1988, a superstorm of fire burned down 800,000 acres of Yellowstone National Park. Due to fire suppression efforts over the twentieth century, a thick layer of dead, organic material had amassed throughout the Snake River Plain—leading to a fire complex so intense that even the plants naturally resistant to ordinary fires were burned to death. The Yellowstone Fire encouraged conservationists and forest ecologists to explore the idea that just because humans do not thrive in the extreme environments of fire, other parts of the ecosystem may. For one thing, low-intensity, frequent fires prevent “super fires” by incinerating the dead material that builds up on the forest floor. Additionally, there are whole, “fire-following” communities of organism that thrive only after a fire. When we suppress fires, we are also suppressing these post-fire communities.
Photo: Yellowstone National Park, National Park Service
As a fire sweeps through, apparently destroying everything in its path, something beautiful happens—often in as little as two-to-three days. Bear Grass is quick to pop back up and eventually grows up to six feet. By next season, a luscious spread of wildflowers that have been dormant since the last fire covers the forest floor. The extreme environment of fire benefits a whole community we are usually not even aware exists. Humans, on the other hand, do not benefit from fire and other extreme environments, so it takes a bit of rethinking to conceptualize an organism that can love something so deadly to us.
Among the most extreme of Earth’s environments are Yellowstone’s hot springs. Because humans tend to underestimate life’s ability to exist in extreme environments, these hot springs were considered too harsh for life. Even microbiologists of the 1960s commonly accepted that bacteria (or anything, for that matter) could not live in extreme temperatures.
However, this changed with a vacation visit to Yellowstone in 1965 by Dr. Thomas Brock, a microbiologist at Indiana University. He became infatuated with the colors of Yellowstone’s hot springs and became convinced that the pink gelatinous masses in the springs were biological—that the common standard of life’s limits was wrong. He then placed a glass slide in a hot spring, watched these microbes take hold and grow, and took what he found back to his lab, to begin growing microbiology’s first cultures of thermophilic bacteria.
Today—nearly 50 years since Brock’s first trip to Yellowstone—the Thermal Biology Institute, an organization of Montana State University, is dedicated to studying the thermophiles found in Yellowstone. Based on previous findings, the Thermal Biology Institute believes that these microbes hold the keys to furthering our progression on everything from alternative energy, to medicine, to agriculture.
A bacterial species cultivated by Brock from the Lower Geyser Basin, later named Thermus aquaticus, became the best-known species living at such extreme temperatures. Most importantly for biotechnology, this species uses a highly thermostable DNA polymerase enzyme to copy its DNA in extremely high temperatures. This enzyme from T. aquaticus led to an easy, simplified version of a critically important reaction in molecular technology—the Polymerase Chain Reaction (PCR). The PCR process allows researchers and students around the world to easily reproduce any targeted segment of DNA in large quantities, and is used widely throughout all areas of biology and biotechnology. Thus, a pink glimmer in a pool of steam and a microbiologist’s rejection of what was already “known,” led to a process still on the forefront of research in biotechnology.
In the extreme heat of Death Valley National Park, one of the most common questions the rangers are asked by visitors is, can anything live out there? Not easily, at least from a human point of view! It turns out that many biological communities in Death Valley are challenged both by heat and geochemical stressors (like high concentrations of salt, copper, lead, tin, and other metals). We recently re-posted one of our features (originally published last March) that explained how Death Valley communities of bacteria that thrive in geochemical stressors could help scientists find life on other planets (specifically, on Mars). Researchers are looking into the traces of organic molecules these microbes leave behind, often referred to as “signatures of life.” For example, bacteria in Death Valley’s geochemically-stressed Badwater pool (at 282 feet below sea level) produce a compound called Rosickyite, which could be a target molecule in the search for life on other planets. If life cannot only tolerate, but thrive in the extreme environments of Death Valley and the Yellowstone Caldera, where (if anywhere) should we stop looking for signs of life?
It is hypothesized that the moons of Jupiter (Ganymede, Europa, and Calisto) while very, very cold, may have liquid water and life—possibly very similar to those extremophiles that inhabit Yellowstone—below the icy surface.
While the bison, the grizzly bear, and the wolf are all common symbols of Yellowstone National Park, what visitors often remember is not their glimpses at these large mammals, but rather, staring for an endless period of time at beautiful, multicolored hot springs, geysers, or even vast skeletons of blackened forests that serve as reminders of our changing fire policies. Look beyond what we think we know, not only below the surface, but also, remember to look towards the stars, because, as Dr. Thomas Brock found, life is often thriving in the places where we least expect it.
Some common marine species and their respective, preferred environments:
Data: “Climate sensitivity across marine domains of life: limits to evolutionary adaptation shape species interactions” Storch, et al.
Studying Growth Temperatures
Researchers often wish to determine the optimal growth temperature and temperature range of newly discovered bacteria. This is accomplished by inoculating a bacterial strain on multiple plates and incubating each plate at a different temperature for a set amount of time. At the end of this incubation, the number of bacterial colonies on each plate is counted. The plate with the most colonies represents the optimal growth temperature, while plates with no colonies represent temperatures above or below the temperature range of the bacterial strain.
Let’s define exactly what thermophiles are. With this name is usually pointed to organisms that can live at high temperatures . In general, it is usually taken as a point of reference those living beings capable of surviving without problems above 45 degrees Celsius. It is worth mentioning that some of these living beings even live in environments as extreme as 75 degrees Celsius and even more than 100 degrees.
It happens that living beings that withstand very high temperatures are part of a biological category called extremophiles . The latter are subdivided as follows:
- xerophite: they are the organisms that can live with very little amount of water, being also called xerophite (this appellative usually is in Botany). They are the ones found in the deserts. There are several bacteria that fit this classification. Also, there are plants that endure long and intense droughts, being located in this category.
- Acidophiles or acidophilic : here they are placed alive beings that manage to survive in sites of great acidity, being an example in this respect the organisms of eukaryotic type. They are rare, although used in various industries as they manage to eliminate other bacteria and prevent their spread.
- Barophiles: they are living beings that live and thrive in places of very high pressure. This type of organisms are those that inhabit the deepest pits of the oceans, as for example the Marianas in the Pacific Ocean. It must be said that these types of living beings manage to withstand very strong pressures, which is why they are very resistant.
- Halophiles: are the organisms that live in environments of enormous salinity. Some examples are the bacteria that develop in the Dead Sea, as well as some crops obtained in salt production sites. They also tend to withstand long periods without the need for water. Sometimes, they combine with the room to eliminate harmful bacteria.
- Oligotrophs: is a very generic name, used both in biology and in botany. It refers to beings that manage to live with very little amount of food. They are small in size, they can also survive in the absence of oxygen.
- Cryptoendoliths: they are the organisms that live to enormous depths in the Earth. Some cases have been found at 2,700 meters depth, even between rocks and high temperatures. Also, they do not usually require a large amount of food.
- Psychrophiles: is the name given to living beings that develop at very low temperatures, which survive the most hostile winters or in places such as the north and south poles. There are registered cases of bacteria that survive at about -30 ° without major inconveniences, this being the type of environment in which they inhabit recurrently.Finally, we want to indicate that thermophiles are just the opposite of Psychrophiles . The living beings that endure extreme and high temperatures in turn are subdivided into two categories. These are the ones we indicate below:
- The simple thermophiles: this category includes living beings with the capacity to live in thermal ranges that range between 45 and 75 degrees Celsius.
- Hyperthermophilic: are living beings living in environments that exceed 75 degrees Celsius. There have been cases of bacteria that live up to 120 degrees. These are usually found in nature in places like geysers and volcanoes.
With all this information, and our readers have an idea about this topic. However, we want to give you more data. Therefore, we invite you to read the paragraphs below. In these segments of the present text, we are going to talk about thermophilic bacteria in foods. Also, the case of the so-called thermophilic forests .
Biology: critters that should not exist!
Astronomers have just discovered two Earth-size, rocky planets around a nearby star. Though the planets are way too broilsome for life, they suggest that steady improvements in telescope technology has made the discovery of habitable planets just a matter of time.
But as astrobiologists continue to search for life in space, geo-biologists (ok, we coined that) continue to find bizarre life in strange places on Earth: in the dark ocean depths, between grains of sand, and at roasty-toasty temperatures once considered deadly.
Hot, humid, and totally alive!
Fifty years ago, nobody believed organisms could survive near the boiling point of water. When Thomas Brock started probing the hot springs in Yellowstone in the 1960s, he was not looking to overthrow a ground rule of biology. Instead, the University of Wisconsin-Madison professor, then at Indiana University, sought to study bacteria in a simplified, real-world environment.
At the time, and even today, precious little was known about how bacteria live their lives — unless they cause disease.
As Brock sampled his way up a hot stream, he approached its source in a hot spring, and the water temperature rose steadily.
At the time, biologists thought life would not tolerate temperatures near 80° C. But Brock kept finding bacteria, so he kept looking. Eventually, he found some that could live and reproduce near the temperature of boiling water — 100° C.
The prize of his collection was a bacterium he named Thermus aquaticus (for its hot-water habitat) and placed in a public repository for study by other scientists.
Over the years, T. aquaticus proved interesting indeed. For one thing, it was the first of more than 50 species of thermophilic bacteria known to tolerate or require temperatures near water’s boiling point.
For another, it was the first of the Archaea (ancient ones), primitive microorganisms that scientists now regard as a separate and highly primitive kingdom of life.
Deep roots indeed
Because thermophiles are Archaeans, and prefer the steamy conditions typical of early Earth, many scientists think they may tell us about the origin of life itself.
To any basic scientist, those contributions would be enough. But because their enzymes work in high temperatures, where chemical reactions are faster, the thermophiles have proven to be extraordinarily useful.
Today, enzymes derived from thermophiles are used to convert millions of pounds of corn (maize) into sugar to sweeten soft drinks.
But more important, at least to scientists who don’t guzzle fizzy pop at the lab bench, T. aquaticus supplied TAQ polymerase, the essential enzyme for polymerase chain reaction, AKA PCR.
PCR is an artificial technique that does what living critters do every day — replicate DNA. But PCR is the rocket ship of replication, since it allows you to multiply a piece of DNA a billion times in a few hours. That produces enough DNA to analyze to your heart’s content — for genetic engineering, biotechnology and forensic purposes.
PCR depends on TAQ polymerase.
Aware that PCR and soda pop are both billion-dollar industries, corporations and scientists around the world have frantically searched for other thermophiles that may have equally useful enzymes. They’re looking in odd places — not just hot springs and volcanoes, but also deep-sea vents, hot petroleum-bearing rock, the outflow of geothermal power plants, and smoldering piles of garbage.
Prowling for glow-in-the-dark squid
Short for bobtail squid. (Did I mention that I’m a 3-4 centimeter cephalopod, formally Euprymna Scolopes?)
Anyway, I hang out in shallow waters around Hawaii. Save your crocodile tears — somebody’s got to live in the sunny, tropical ocean. Anyway, here’s my problem: Even though I have 10 tentacles, I don’t have spines, poisons, or any other decent defense.
So I spend my days burrowed in sand at the ocean bottom, trying to keep out of mischief. Still, a fellow’s got to eat, don’tcha know, so I cruise at night, looking to grab a bite.
Here’s the snag: All sorts of nocturnal predators seem to have this thing about calamari sushi.
Light before flashlights
A long time ago, my ancestors evolved a nifty defense against their big teeth: stealth. Even their tiny squid brains figured out that predators could see them from below, as tasty dark blobs against the bright ocean surface.
Since this was before flashlights, my relatives had to improvise. So they press-ganged billions of luminescent bacteria into making light for them. The idea was to make us just as bright as the ocean surface — and hence invisible.
At least, this is how my great-aunt Tentacla tells it. To tell the truth, I think it had more to do with the evolutionary advantage of being hard to see.
Anyway, my ancestors fed the bacteria, and gave them a home in two specialized light-emitting organs. These “photophores” have a reflective membrane to shine all their light down, toward the hungry predators. They use a diaphragm to control brightness, and even have a lens to spread the light.
The photophore reminds me of a backwards eye — one that makes light rather than detects it.
My folks even figured out how to switch the bacteria “on” when needed.
In return, the bacteria got room and board, in the biological deal they call “symbiosis” or “mutualism.” Sometimes I think people could learn from this cooperative spirit….
But that’s enough thinking for today. My squid brain is squashed.
As I burrow into the sand for another daytime nap, permit me to introduce somebody who considers me almost as fascinating as I do.
Margaret McFall-Ngai, a biologist at University of Wisconsin-Madison, says the bobtail squid may pretend it’s cooperating in a symbiosis with those light-making bacteria, but the reality is more ominous.
She says there’s evidence that this may be slavery, not symbiosis, since the squid, “inhibits the growth of the bacteria to enhance their luminescence.” The bacteria, Vibrio fischeri, could make a better living drifting in the ocean, or in the gut of another marine animal, McFall-Ngai observes.
The concept of bacterial enslavement broadens our perspective on the many possible relationships in the living world.
Most people, if they think about bacteria at all, conjure up disease and decay, but people would be dead without bacteria, since the little critters play essential roles in producing vitamins and preventing disease.
Since the bacteria in our guts vastly outnumber the cells in our bodies, it helps that they’re helpful!
Nevertheless, and for understandable reasons, bacteriologists have traditionally focused on disease-causing organisms, and, for simplicity, on one species at a time. But that skews our view of how bacteria actually live, says McFall-Ngai.
Three cheers for complexity!
Complexity and subtlety may be the hallmarks of these interactions, and the complexity begins by recognizing that V. fischeri is closely related to V. cholerae, which causes the human intestinal disease, cholera.
Cholera is caused by a V. cholera toxin similar to a toxin produced by the light-emitting bacterium. But far from harming the poor little bobtail, that toxin signals it to secrete food for V. fischeri, so the toxin is really a chemical “dinner bell.”
And this raises the intriguing notion that a cholera bug secretes toxins not to kill its host but to discuss its menu. If so, our whole notion of pathogenesis may need rewriting, McFall-Ngai suggests. “Maybe when we’ve been studying cholera pathogenesis we’ve been studying an aspect of a normal conversation that’s gone wrong.”
Indeed, the traditional bacteriological view of bacteria as pathogens to be studied in pure culture may be “like trying to understand the complexity of all the cultures that lived in Paris by studying the activity of the Nazi occupiers,” McFall-Ngai suggests. “You are studying groups that don’t belong there, and have disrupted the normal activities.”
Want more on how the flashlight squid bullies its bacterial brethren?
Between the grains
(1996 story, only photos have been updated)
To zoologist Robert Higgins, small is beautiful. His infatuation with small creatures — “meiofauna” — dates to a student job in a biology lab that paid 35 cents an hour. Instead of quitting for more lucrative work, Higgins was intrigued.
He’d heard about tiny, amazingly diverse creatures, and put grains of sand and muck through a fine mesh, and used a microscope to find hundreds of organisms.
Forty-four years later, Higgins has retired from the Smithsonian Institution, but he’s still goggling at meiofauna — a complex group of animals found in most Earthly environments.
Indeed, a handful of wet sand could contain more biological diversity than a whole rain forest, Higgins says.
In the course of peering through countless microscopes, Higgins has discovered hundreds of species. With Danish biologist Reinhardt Kristensen, he found an entire phylum, called Loricifera.
Phyla are the broadest categories of organisms, based on structure, and according to the International Association of Meiobenthologists, “The majority of recognized phyla have meiofaunal representatives. Currently, 20 phyla considered to be meiofaunal from the 34 recognized phyla of the Kingdom Animalia. Out of these 20 phyla, five are exclusively meiofaunal in size.”
Meiofauna living between grains of sand have made some fancy adaptations to their harsh environment. Some have hooks on their feet, used to grab the sand. Others have hooked mouthparts, also useful for locomotion.
To survive a difficult environment, meiofauna called tartigrades have evolved an amazing adaptation called “anhydrobiosis.” In this form of suspended animation, the animals replace water in their cell membranes with sugar, protecting the membrane from destruction through radiation and freezing. Microorganisms die when their cell membrane ruptures.
During anhydrobiosis, organisms are rather like plant seeds or bacterial spores, Higgins explains. “They can dry up for 100 years, and be rewetted, and come right back to active metabolism.”
Fun is fun. But what is the practical importance of studying stuff that can hardly be seen, doesn’t seem to cause disease, and is — at least to some — utterly ugly?
In other word, who cares about microscopic beach crud?
Meet the beach-cleaning crew
Anybody who likes to hang on the sand should be interested, Higgins says. “This is the system that helps keep our beaches clean.” Plankton, bacteria, all sorts of dead material is continually washing ashore, and a lot of people love to sit on beaches.
There’s a public-health angle here. Hookworms occur on beaches where dogs defecate, but meiofauna may consume hookworms, along with other nematodes. “So if we upset that, we could upset beach cleanliness,” Higgins says.
Higgins notes that meiofauna comprise a basic part of the food web, and disturbing them could have unforeseen consequences for the entire system.
Still, it’s hard to escape the notion that most of the motivation here is the pure scientific urge to discover, to classify, to understand. Meiofauna, Higgins notes, were seen under the microscope Anton van Leeuwenhoek invented in 1683.
The key to finding these things, Higgins indicates, in patience, technology, curiosity — and institutional support. “If you stare through a microscope for hour after hour, you have a chance of finding these things, but if you need to get out a certain number of papers each year, you have to take shortcuts and you won’t find as much.”
Fantastic freak show
Biology has lots of other oddities:
A shrimplike native to Panama’s Pacific beaches transports itself by rolling. When the animal washes ashore, it arcs its body into a ring and rolls back into the water, pushed by the head and tail at the stately pace of 3.5 centimeters per second. Nannosquilla decernspinosa may have learned to spin in its cramped burrows, but it’s the only known rolly-roller in the animal kingdom.
Sponges, considered the first multicellular organisms, were always thought to be dumb, simple filter-feeders that strain their dinner from sea water. But now it appears that some sponges in the phylum Cladorhizidae, living in the Mediterranean, are willing to reach out and touch their prey. The sponge has filaments that capture plankton and reel them in for digestion.
Bacteria can live deep underground, and in 2006 a team found bacteria 3 kilometers below South Africa, in a niche that had been isolated from the surface for several million years. The discovery demonstrates the resilience of life on Earth and hints that life could exist deep inside Mars.
A large number of ancient bacterial relatives — Archaea — live in the Antarctic. These critters are a large part of the food web in a cold, remote place whose ocean is a major source of protein in our diet.
Thermus thermophilus as biological model
Thermus spp is one of the most wide spread genuses of thermophilic bacteria, with isolates found in natural as well as in man-made thermal environments. The high growth rates, cell yields of the cultures, and the constitutive expression of an impressively efficient natural competence apparatus, amongst other properties, make some strains of the genus excellent laboratory models to study the molecular basis of thermophilia. These properties, together with the fact that enzymes and protein complexes from extremophiles are easier to crystallize have led to the development of an ongoing structural biology program dedicated to T. thermophilus HB8, making this organism probably the best so far known from a protein structure point view. Furthermore, the availability of plasmids and up to four thermostable antibiotic selection markers allows its use in physiological studies as a model for ancient bacteria. Regarding biotechnological applications this genus continues to be a source of thermophilic enzymes of great biotechnological interest and, more recently, a tool for the over-expression of thermophilic enzymes or for the selection of thermostable mutants from mesophilic proteins by directed evolution. In this article, we review the properties of this organism as biological model and its biotechnological applications.
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Watch the video: Extremophiles 101. National Geographic (January 2023).