Archaea, or primordial bacteria, are cellular life forms in addition to the other groups of bacteria and eukaryotes. In the late 1970s, the archaea were described and classified as a distinct group by microbiologists Carl Woese and George Fox.
What are archaea?
Archaea are single-celled organisms that possess DNA (deoxyribonucleic acid) in the form of a circular chromosome. Thus, they do not possess a nucleus. Therefore, archaea are also referred to as having a nuclear equivalent. The Archaea are assigned to the prokaryotes. They do not have cell organelles but a cytoskeleton to stabilize the cell. The Archaea are described as a separate group, because they have a different sequence of ribosomal RNA (ribonucleic acid). Specifically, this concerns the sequence of the RNA of the small ribosomal subunit, the 16sRNA. The ribosomes serve to translate the protein during the synthesis of new proteins. Archaea are structurally more similar to eukaryotes than to prokaryotes.
Occurrence, distribution, and characteristics
Archaea occur in areas of the world with particularly extreme conditions. There are archaea that require temperatures above 80 degrees Celsius to survive. This form of archaea is called hyper-thermophilic. Other archaea prefer a very high concentration of salt in the solution in which they live. These are described as halophilic. In addition, there are those that require a particularly acidic environment to live. At pH values as low as 0, the environment is acidic and the archaea are described as acidophilic. Alkalophilic archaea prefer a basic environment with a pH value of up to 10. Barophilic archaea are found in environments subject to high pressure. They are often found in volcanic hot springs, such as in Yellowstone Natinal Park, where they were first discovered. The forms that are accustomed to high salinity are found, for example, in the Dead Sea in Israel. Methanogenic archaea live under anoxic conditions. They utilize hydrogen in their metabolism to produce energy. They occur in fresh water, soil and also in the sea. They can also live in the form of symbiosis in the intestines of humans and animals. Archaea also have some similarities to bacteria. Cell division takes place in a similar way and both do not have a nucleus. The cell size is also very similar to that of bacteria. The genes of both organisms are divided into so-called operons. These are DNA units consisting of promoter, operator and gene. These are more commonly found in prokaryotes, but are also occasionally found in eukaryotes. And both have similar means of locomotion, the flagellum. However, the ribosomal RNA of archaea is more complicated in structure than that of bacteria. Protein biosynthesis, that is, transcription and translation, occurs in archaea in much the same way as in eukaryotes. They have very similar initiation and elongation factors that start protein biosynthesis. Archaea also possess a TATA box. This is a region of DNA with many thymidines and adenines. It is located in the promoter region, so it is usually upstream of the coding gene. The fatty acids of the cell membrane are not linked to glycerol molecules compared to bacteria and eukaryotes. Some subspecies of archaea have a cell wall, which can vary greatly within archaea. This is due to the environment in which the respective archaea live. In addition, archaea can move relatively fast. They are autotrophic organisms. They produce carbon by absorbing and converting carbon dioxide. There are also some that are heterotrophic. They make carbon from organic compounds that they ingest. Most archaea are anaerobic, they do not require oxygen, which can even be toxic to them. They are further divided into chemoorganotrophic or chemolithotrophic. They gain energy from metabolizing organic or inorganic compounds.
Importance and function
Archaea live in symbiosis with humans. They are found in humans in the mouth, the intestine, and also the vagina. They are often Methanobrevibacter smithii, which is a methanogenic archaea. No archaea have yet been detected in infants younger than 2 years of age. Mainly archaea are found in the intestinal tract of humans. Together with syntrophic bacteria, archaea play a role in digestion.Syntroph’ means the ‘mutual living together’ of different organisms. They produce different substances, which can be used by the other organism. In this case, the organisms are interdependent. Archaea use the hydrogen produced by bacteria for their methanogenesis. In the process, archaea also break down methane, which is toxic to humans. They have a positive effect on human digestion.
Diseases and ailments
Archaea are not pathogenic to humans. However, increased levels of methanogenic archaea have been found in the intestines of people with colon cancer. Also, increased numbers of them were found in inflamed gums, and a correlation between the number of them and the severity of periodontitis was demonstrated.
