Chemosynthesis is an autotrophic nutrition method in which the oxidation of inorganic compounds serves as the energy source for the synthesis of organic substances from CO 2 . This type of energy production is used only by bacteria or archaea . This phenomenon was discovered in 1889 by the Russian scientist S. N. Vinogradsky . Microorganisms capable of chemosynthesis, Vinogradsky called anoroxidants . The name chemosynthesis was introduced by the German chemist and botanist Wilhelm Pfeffer in 1897.
It should be noted that the energy released in the oxidation reactions of inorganic compounds cannot be directly used in the processes of assimilation . At first, this energy is transferred to the energy of macroenergy ATP bonds and only then is spent on the synthesis of organic compounds.
Content
Chemolithoautotrophic organisms
- Iron bacteria ( Geobacter , Gallionella ) oxidize bivalent iron to trivalent.
- Sulfur bacteria ( Desulfuromonas , Desulfobacter , Beggiatoa ) oxidize hydrogen sulfide to molecular sulfur or to salts of sulfuric acid .
- Nitrifying bacteria ( Nitrobacteraceae , Nitrosomonas , Nitrosococcus ) oxidize ammonia formed in the process of rotting of organic substances, to nitrous and nitric acids , which, interacting with soil minerals , form nitrites and nitrates .
- Thionic bacteria ( Thiobacillus , Acidithiobacillus ) are able to oxidize thiosulfates , sulfites , sulfides, and molecular sulfur to sulfuric acid (often with a significant decrease in the pH of the solution), the oxidation process differs from that of sulfur bacteria (in in particular, the fact that thionic bacteria do not deposit intracellular sulfur). Some representatives of thionic bacteria are extreme acidophiles (able to survive and multiply when the pH of the solution drops to 2), can withstand high concentrations of heavy metals and oxidize metal and ferrous oxide ( Acidithiobacillus ferrooxidans ) and leach heavy metals from ores .
- Hydrogen bacteria ( Hydrogenophilus ) are capable of oxidizing molecular hydrogen, are moderate thermophiles (grow at 50 ° C)
Dissemination and environmental functions
Chemosynthesizing organisms (for example, sulfur bacteria ) can live in the oceans at great depths, in those places where hydrogen sulfide enters the waters of the crust. Of course, light quanta cannot penetrate the water to a depth of about 3-4 kilometers (most of the ocean’s rift zones are at this depth). Thus, chemosynthetics are the only organisms on Earth that are independent of the energy of sunlight and are primary producers . Chemosynthetic organisms can be consumed by other organisms in the ocean or form symbiotic associations with heterotrophs. Giant polychromic worms use bacteria in their trophosome x to bind carbon dioxide (using hydrogen sulfide as an energy source) for the production of sugars and amino acids [1] . Some reactions produce sulfur [2]
- 12 H 2 S + 6C O 2 → C 6 H 12 O 6 (= carbohydrates ) + 6 H 2 O + 12S:
Instead of releasing oxygen when carbon dioxide is fixed during photosynthesis , water-soluble sulfur globules are obtained from hydrogen sulfide during the process of chemosynthesis. In bacteria capable of chemoautorophy in the form of chemosynthesis, such as purple sulfur bacteria [3] , purple sulfur globules stain the cytoplasm in the appropriate color. Large populations of animals can be maintained due to chemosynthetic bacteria and archaea in white and black smokers , methane clathrates , cold infiltrations , the corpses of whales , isolated underground water caves .
On the other hand, ammonia, which is used by nitrifying bacteria, is released into the soil when rotting plant or animal residues. In this case, the vital activity of chemosynthetics is indirectly dependent on sunlight, since ammonia is formed during the decomposition of organic compounds produced by the energy of the Sun.
The role of chemosynthetics for all living beings is very large, as they are an indispensable element of the natural circulation of the most important elements: sulfur, nitrogen, iron, etc. Chemosynthetics are also important as natural consumers of toxic substances such as ammonia and hydrogen sulfide. Of great importance are nitrifying bacteria, which enrich the soil with nitrates and nitrites - a form of nitrogen , mostly absorbed by plants. Some chemosynthetics (in particular, sulfur bacteria) are used for wastewater treatment.
According to modern estimates, the biomass of the “underground biosphere”, which is, in particular, under the seabed and includes chemosynthesizing anaerobic methane-oxidizing archaebacteria , may exceed the biomass of the rest of the biosphere. [four]
It was hypothesized that chemosynthesis can support life under the surface of Mars , the satellite of Jupiter - Europe and other planets [5] . Chemosynthesis can also be the first type of metabolism that originated on Earth, which later led to the emergence of cellular respiration and photosynthesis .
See also
- Lithotrophs # Representatives
- Photosynthesis
- Autotrophs
- Heterotrophs
- Radio synthesis
Notes
- ↑ Biotechnology for Environmental Management and Resource Recovery . - Springer, 2013. - p. 179. - ISBN 9788132208761 .
- ↑ Campbell NA ea (2008) Biology 8. ed. Pearson International Edition, San Francisco. ISBN 978-0-321-53616-7
- ↑ The purple phototrophic bacteria . - Dordrecht: Springer, 2009. - ISBN 9781402088148 .
- ↑ Elements - science news: At a depth of 1626 m under the level of the seabed, rich microbial life was discovered
- ↑ Julian Chela-Flores (2000): "Terrestrial Microsites as Candidates for Mars and Europa", in: Seckbach, Joseph (ed.) Microbial Worlds: Adaptation to Exotic Environments , Springer, pp. 387–398. ISBN 0-7923-6020-6