THERMUS AQUATICUS: CHARACTERISTICS, LIFE CYCLE, APPLICATIONS - BIOLOGY - 2025

Thermus aquaticus is a thermophilic bacterium, discovered by Thomas Brock in 1967, located in the Phylum Deinococcus-Thermus. It is a gram-negative, heterotrophic and aerobic microorganism, which has thermal stability as an intrinsic property.

It is obtained from a variety of hot springs between 50 ° C and 80 ° C, and pH 6.0 to 10.5, in Yellowstone National Park and in California in North America. It has also been isolated from artificial thermal habitats.

Thermus aquaticus. Bacteria deposited on a 0.22 μm Millipore filter (scale = 1 μm).

It constitutes a source of heat resistant enzymes, which survive the different cycles of denaturation. In this context, proteins and enzymes are of special interest to the biotechnology industry.

This is how the enzymes that compose it are used in genetic engineering, in the polymerase chain reaction (PCR), and as a scientific and forensic research tool (Williams and Sharp, 1995).

General characteristics

Yellowstone Park Geyser. Thermus aquaticus was isolated from a geyser. Source: Pixabay

It is gram negative

Thermus aquaticus, when subjected to the Gram staining process, acquires a fuchsia coloration. This is because the peptidoglycan wall is extremely thin so that the dye particles are not trapped in it.

Habitat

This bacterium is designed to withstand extremely high temperatures. This implies that their natural habitat is places on the planet where temperatures exceed 50 ° C.

In this sense, this bacterium has been isolated from geysers, the most common being those of Yellowstone National Park; from hot springs around the world, as well as from artificial hot water environments.

It's aerobic

This means that Thermus aquaticus is a bacterium, it must be in environments that provide it with oxygen availability in order to carry out its metabolic processes.

Is thermophilic

This is one of the most representative characteristics of Thermus aquaticus. This bacterium has been isolated from places where temperatures are extremely high.

Thermus aquaticus is a very special and resistant bacterium, since at temperatures as high as those it supports, the proteins in most living beings are denatured and irreversibly cease to fulfill their functions.

This bacterium has a growth temperature that ranges from 40 ° C to 79 ° C, with the optimum growth temperature being 70 ° C.

It is heterotrophic

Like any heterotrophic organism, this bacterium requires organic compounds present in the environment in order to develop. The main sources of organic matter are bacteria and algae present in the surroundings, as well as the surrounding soil.

It thrives in slightly alkaline environments

The optimum pH in which Thermus aquaticus can develop without the proteins that comprise it losing their function is between 7.5 and 8. It is worth remembering that on the pH scale 7 is neutral. Above this it is alkaline and below it acidic.

Produces a large number of enzymes

Thermus aquaticus is a microorganism that has been very useful at an experimental level due to its ability to live in environments with high temperatures.

Well, through numerous investigations it has been determined that it synthesizes numerous enzymes that, curiously, in other microorganisms, at the same temperatures, become denatured and lose their function.

The enzymes synthesized by Thermus aquaticus that have been most studied are;

• Aldolasse
• Taq I restriction enzyme
• DNA ligase
• Alkaline phosphatase
• Isocitrate dehydrogenase
• Amylomaltase

Phylogeny and taxonomy

This microorganism is framed under the classical approach:

• Kingdom: Bacteria
• Phylum: Deinococcus- Thermus
• Class: Deinococci
• Order: Thermales
• Family: Thermaceae
• Genus: Thermus
• Species: Thermus aquaticus.

Morphology

The bacteria Thermus aquaticus belongs to the group of rod-shaped bacteria (bacilli). Cells are approximately 4 to 10 microns in size. Very large cells can be seen under the microscope, as well as small cells. They do not have cilia or flagella on the cell surface.

The Thermus aquaticus cell has a membrane that in turn is made up of three layers: an internal plasma layer, an external rough-looking and an intermediate layer.

One of the distinguishing characteristics of this type of bacteria is that there are structures that look like rods in its inner membrane, which are known as rotund bodies.

Likewise, these bacteria contain very little peptidoglycan in their cell wall and, unlike gram-positive bacteria, it contains lipoproteins.

When exposed to natural light, the bacteria's cells can turn yellow, pink, or red. This is due to the pigments that are contained in the bacterial cells.

The genetic material is made up of a single circular chromosome in which DNA is contained. Of this, approximately 65% ​​is made up of Guanine and Cytosine nucleotides, with Thymine and Adenine nucleotides representing 35%.

Lifecycle

In general, bacteria, including T. aquaticus, reproduce asexually by cell division. The single DNA chromosome begins to replicate; it replicates to be able to inherit all the genetic information to the daughter cells, due to the presence of the enzyme called DNA polymerase. Within 20 minutes the new chromosome is complete and has fixed in place in the cell.

The division continues and after 25 min, the two chromosomes have begun to duplicate. A division appears in the center of the cell and at 38 min. the daughter cells present the division separated by a wall, ending the asexual division at 45-50 min. (Dreifus, 2012).

Cell structure and metabolism

Because it is a gram-negative bacterium, it has an outer membrane (lipoprotein layer) and periplasm (aqueous membrane), where the peptidoglycan is located. No cilia or flagella are observed.

The composition of the lipids of these thermophilic organisms must adapt to fluctuations in the temperature of the context where they develop, to maintain the functionality of the cellular processes, without losing the chemical stability necessary to avoid dissolution at high temperatures (Ray et al. 1971).

On the other hand, T. aquaticus has become a true source of thermostable enzymes. Taq DNA polymerase is an enzyme that catalyzes the lysis of a substrate by generating a double bond, so it is related to lyase-type enzymes (enzymes that catalyze the release of bonds).

Since it comes from a thermophilic bacteria, it resists long incubations at high temperatures (Lamble, 2009).

It should be noted that each organism has DNA polymerase for its replication, but due to its chemical composition it does not resist high temperatures. That is why taq DNA polymerase is the main enzyme used to amplify sequences of the human genome, as well as genomes of other species.

Applications

Amplify fragments

The thermal stability of the enzyme allows it to be used in techniques to amplify DNA fragments through in vitro replication, such as PCR (polymerase chain reaction) (Mas and Colbs, 2001).

This requires initial and final primers (short nucleotide sequence that provides a starting point for DNA synthesis), DNA polymerase, deoxyribonucleotides triphosphate, buffer solution and cations.

The reaction tube with all the elements is placed in a thermal cycler between 94 and 98 degrees Celsius, to divide the DNA into single strands.

The performance of the primers begins and reheating occurs again between 75-80 degrees Celsius. Initiates synthesis from the 5 ′ to 3 ′ end of DNA.

Here is the importance of using the thermostable enzyme. If any other polymerase were used, it would be destroyed during the extreme temperatures necessary to carry out the process.

Kary Mullis and other researchers at Cetus Corporation found the exclusion of the need to add enzyme after each cycle of thermal denaturation of DNA. The enzyme was cloned, modified, and produced in large quantities for commercial sale.

Catalyze biochemical reactions

The hydrolysis of gluten by the thermoactive serine peptidase aqualysin1 from T. aquaticus, begins above 80 ° C in bread making.

With this, the relative contribution of heat-stable gluten to the texture of the bread crumb is studied (Verbauwhede and Colb, 2017).

Degradation of polychlorinated biphenyl compounds

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