Thermus aquaticus*

From MicrobeWiki, the student-edited microbiology resource

A Microbial Biorealm page on the genus Thermus aquaticus*

Classification

Higher order taxa

Bacteria; Deinococcus-Thermus; Deinococci; Themales; Thermophilus; Aquaticus

Species

Thermus Aquaticus

T-aquaticus.gif.jpeg [5]

Description and significance

Thermus Aquaticus is a typical gram negative bacteria, meaning that its cell walls contain much less peptidoglycan than their gram positive cousins, and unlike gram positive bacteria, gram negative bacteria contain lipoproteins. Thermus Aquaticus appears as either a rod or short filaments, and the rod-shaped cells will tend to form either a rosette or a linear pattern [1]. When exposed to sunlight, Thermus can exhibit a yellow, pink, or red color due to pigments within the bacteria. Along with the coloration, Thermus Aquaticus can either have flagella or be immotile.

Thermus Aquaticus has proven to be quite a useful organism in the field of Biotechnology, as its enzyme Taq polymerase is harvested for use in polymerase chain reactions (PCR). The reason Taq polymerase is used in PCR, as opposed to other forms of the polymerase enzyme is because Thermus Aquaticus' form of the enzyme is well-suited for the repetitive heating involved in PCR and will not denature. Taq polymerase's resistance to heat is an adaptation to its environment, but is not the only reason it is the choice for use in PCR. Taq polymerase is also chosen because it is incredibly accurate, at 1x10^-4 to 2x10^-5 errors per base pair [2], and does not need to be completely pure to be effective [3]. These properties of Taq polymerase- it's heat resistance, accuracy, and potency- make PCR, and technologies that utilize PCR, such as DNA fingerprinting, enzyme production, and medical diagnoses possible.

Genome structure

Several studies have agreed that the base pair composition of an average Thermus Aquaticus DNA molecule is between 57 - 65% for G + C meaning that the corresponding base pairs of A+T, have a composition of 35 - 43%. DNA strains for T. aquaticus are naturally transferable which means that, under normal physiological conditions, they can be directly incorporated after they are taken up.I The distinguishing feature of T. aquaticus's genomic structure is the 16s rRNA gene.III This is what differentiates it from all other thermophiles. Two studies have demonstrated that T. aquaticus has 4 plasmids while another study claims it to have 5 but the results differed between the colonies. In any case "coherent circular restriction endonuclease maps have been published for only 4," (160) [6].

Cell structure, metabolism & life cycle

The bacterial species Thermus Aquaticus is Heterotrophic in nature and, consequently, needs organic compounds from the surrounding environment in order to grow and sustain life. Some of the most common sources for organic material are as follows: the algal-bacterial mat, other heterotrophs, chemoautotrophs, and the surrounding soil. The algal-bacterial mat is an area at the surface of a hot springs environment containing decomposing organic matter, and is thought to be a major source of organic compounds for T. aquaticus. Another source is that of dead heterotrophs chemoautotrophs already present in the bacteria's environment. It is also believed that organic matter is present in the runoff of the surrounding soil [6]. Thermus Aquaticus belongs to the Deinococcus-Thermus group. It is one of the first Archaea to be discovered. They are really ancient microorganisms, which existed in the first stages of the earth’s history.

Thermus aquaticus’ structure resembles that of other gram-negative bacteria. It has a three layered membrane composed of an inner plasma membrane, an intermediate and a rougher outer layer. Along the inner membrane usually lies a series of rod like structures that resemble individual cells, which are called rotund bodies. These cell like structures are the most unique characteristic of Thermus Aquaticus. The rest of its anatomy is just like other bacteria. However, there are no flagella or cilia present in Thermus Aquaticus, suggesting that this bacterium is immotile [1].

Ecology (including pathogenesis)

The temperature of an environment can be considered one of the most influencial factors in determining the composition of the specific ecosystem. For example geothermal springs have a very high temperature range, and, as a result, the organisms that live there must be able to cope with such conditions. Thermus aquaticus was first found in several of the Yellowstone National Park hot springs. It can survive at temperatures of 55-100 degrees Celsius in weakly acidic to alkaline (pH 5-9) waters. It was also discovered in marine thermal springs, low saline solfataric springs and thermally polluted waters. The ideal conditions for this organism to grow are around 70 to 75 degrees Celsius at a pH of 7.5 to 8 [4]. There are also some other environmental factors to consider, such as: the oxygen and nitrate concentration and the effects of light and salinity. Since these organisms exist at high temperatures, there is only a small amount of dissolved oxygen in the water. Because of this it is assumed that Thermus can use nitrate as their terminal electron acceptor instead of oxygen. It seems as though high concentrations of sulfide do not greatly affect the number of organisms. The degree of salinity does seem to affect them though. While there are some strains of Thermus that are halotolerant, there are none that are halophillic, and T. aquaticus is very sensitive to changes in salinity. Its growth is inhibited even if there is a 0.5% concentration of NaCl and cannot grow in any system with NaCl concentrations above 1% [6].

Biogeosciences.jpg [7] This is a hot spring similar to the one that Thermus aquaticus was discovered in.

Interesting feature

Thermus aquaticus’ structure resembles that of other gram-negative bacteria. It has a three layered membrane composed of an inner plasma membrane, an intermediate and a rougher outer layer. Along the inner membrane usually lies a series of rod like structures that resemble individual cells, which are called rotund bodies. These cell like structures are the most unique characteristic of Thermus Aquaticus. The rest of its anatomy is just like other bacteria. However, there are no flagella or cilia present in Thermus Aquaticus, suggesting that this bacterium is immotile [1].

References

[1] Brock, Thomas D. and Mercedes R. Edwards. Journal of Bacteriology, Oct 1970, Vol 104. p 509-517. “Fine Structure of Thermus aquaticus, an Extreme Thermophile.”

[2] “Thermostable DNA Polymerases.” http://www.vivo.colostate.edu/hbooks/genetics/biotech/enzymes/hotpolys.html. 9/26/2007.

[3] “PCR (Polymerase Chain Reaction) – HIV: health and medical information about HIV and..” http://www.medicinenet.com/pcr_polymerase_chain_reaction/page2.htm. 9/25/2007.

[4] “Thermus aquatics.” Wikipedia. http://en.wikipedia.org/wiki/Thermus_aquaticus

[5] Townsend, Rich. "Terrestrial Life in Extreme Environments." http://zuserver2.star.ucl.ac.uk/~rhdt/diploma/lecture_6/. 2/18/2003.

[6] Biotechnology Handbooks 9 - Thermus Species. Edited by Richard Sharp and Ralph Williams. Published by Pelnum Press, NY. 1995.

[7] http://www.sci.uidaho.edu/guerrilla-hydrology/Images/biogeosciences.jpg