Use of knowledge about the biogeochemical activity of microorganisms in biology lessons. General concept of the biosphere
At the present stage of development, the main goal facing school education, including biological education, is the preparation of a cultured, highly educated person, a creative person. The solution of this global task is aimed at the revival of spiritual, moral traditions, introducing students to the culture created over the thousand-year history of mankind, the formation of a new style of thinking - biocentric, without which it is impossible to preserve life in the biosphere.
Biology makes a significant contribution to the formation of a scientific picture of the world among schoolchildren, a healthy lifestyle, hygienic norms and rules, environmental literacy; in preparing young people for work in the field of medicine, agriculture, biotechnology, environmental management and nature protection. (3.6)
The content of biological education includes knowledge about the level of organization and evolution of living nature; biodiversity; metabolism and energy conversion; reproduction and individual development of organisms, their relationship with the environment and adaptability to it; about the organism, its biological nature and social essence; sanitary and hygienic norms and rules of a healthy lifestyle. (4.6)
The implementation of these tasks is carried out through programs and educational and methodological education. Currently, there are several educational and methodological sets in biology. The teacher can choose one of them, taking into account the characteristics of the regions, the level of preparation of students, the specialization of education at school.
It depends on the choice of the program in what sequence and how deeply the students will study the material.
According to the program of Sivoglazov V.I., Sukhova T.S., Kozlova T.A. in the teacher's book "Biology: General Patterns", the topic "Biogeochemical activity of microorganisms" is not considered as an independent one in a separate lesson, but is an integral part of other topics. For example, in a lesson on the topic “The importance of prokaryotes in biocenoses, their ecological role”, such issues as the participation of bacteria in all processes occurring in the organic world on Earth are studied; the role of bacteria in the cycle of substances that provide life on Earth, as well as the participation of bacteria in the cycle of the most important elements. In the lesson on the topic "Circulation of substances in nature", along with other issues, the activity of nitrogen-fixing bacteria is considered, due to which atmospheric nitrogen is included in the cycle, and the activity of microorganisms involved in the cycle of carbon and sulfur is also considered.
Let's take a closer look at these lessons.
THE SIGNIFICANCE OF PROKARYOTES IN BIOCENOSES, THEIR ECOLOGICAL ROLE»
Reference points of the lesson
Bacteria as primitive life forms that live everywhere: in water, in soil, in food products, in all geographical areas of the Earth
The participation of bacteria in all processes occurring in the organic world on Earth
The role of bacteria in the cycle of substances that provide life on Earth
Participation of bacteria in the cycle of essential elements
Pathogenic bacteria, their role in the wild and in a civilized society
Bacteria and food industry
The role of bacteria in agriculture
Cyanes (blue-green) - the most ancient of the organisms containing chlorophyll
The indicator role of cyanides (blue-green) as indicators of the degree of pollution of water bodies.
Tasks:
1. Describe all possible habitats for prokaryotes on our planet.
2. Justify the "omnipresence" of bacteria and cyanides (blue-green) by the features of their structure, physiological processes and life cycles.
3. To form students' knowledge about the important ecological role of prokaryotes.
Answer the questions. Complete the tasks:
1. What is the structure of a bacterial cell?
2. Describe the sexual process of bacteria.
3. On the basis of what features inherent in blue-greens can they be classified as prokaryotes?
4. Fill in the diagram revealing the role of bacteria in nature and in human life.
The role of bacteria in nature and in human life
1..... 3..... 5.....
play an important role in the biosphere bacteria that populated the hydrosphere, the atmosphere to the greatest extent - the lithosphere. The speed of their reproduction and vital activity affects the circulation of substances in the biosphere.
Basic provisions
1. In the biosphere, a constant circulation of active elements takes place, passing from organism to organism, to inanimate nature and back to the organism. The main role in this process is played by decay bacteria.
2. Prokaryotes, by virtue of their ability to reproduce rapidly, have enormous genetic variability and adaptability. Bacteria are divided into several groups according to the way they feed and use energy.
3. The adaptation of each group of bacteria to specific environmental conditions (narrow specialization of life activity) leads to the fact that some bacteria are replaced by others in the same environment. For example, putrefactive bacteria decompose organic residues in the soil, releasing ammonia, which other bacteria convert into nitrous acid and then into nitric acid. The greatest process in the biosphere, carried out by bacteria, is the decomposition during decay of all the dead bodies of all the inhabitants of the Earth.
reference
Water, 1 ml of which contains 10 bacteria, remains clear, not cloudy.
Question for thought . Why did L. Pasteur call bacteria "the great gravediggers of nature"?
Questions and tasks for repetition.
1. Under the influence of what organisms does the complete decomposition of the organic matter of dead individuals on our planet occur?
2. The influence of what environmental factors can contribute to the destruction of bacteria?
3. Why will soil pollution with oil products have a sharp negative impact on the state of the entire biogeocenosis?
4. Why do bacteria belong to the group: decomposers in any biogeocenosis?
5. How can pathogenic bacteria affect the state of a macroorganism (host)?
6. In what cases can mass reproduction of blue-greens be observed in reservoirs? What can this lead to?
Information for the teacher
Bacteria and cyanide (blue-green) are ubiquitous. Bacterial spores fly to a height of 20 km, anaerobic bacteria penetrate the earth's crust to a depth of more than 3 km.
Spores of some bacteria remain viable at a temperature of - 253°C. There are over 600 billion individuals in one gram of bacteria. The number of bacteria in one gram of soil is measured in hundreds of millions.
Additional task
Write an essay on the topic: "A week without bacteria on Earth."
Prokaryotes carry out photosynthesis differently than plants. Bacteria use the pigment bacteriochlorin in this process.
and do not release oxygen into the environment. Photoautotrophic archaebacteria carry out photosynthesis with the help of bacteriorhodopsin, and cyanobacteria, in addition to chlorophyll, additionally have two other pigments: phycocyanin and phycoerythrin. These facts show that nature has provided several pigments for the implementation of the synthesis of primary organic matter, which significantly expand the spectral composition of the radiation available for photosynthesis. Chemosynthesis is very common among prokaryotes. In addition, among bacterial organisms there are nitrogen-fixing forms: this is the only group of living organisms on our planet that are able to assimilate nitrogen directly from atmospheric air and thus involve molecular nitrogen in the biological cycle.
Bacteria and blue-greens include up to 90% of all nitrogen included in the biogenic cycle in the composition of organic matter; the remaining 10% of the nitrogen is bound by lightning electrical discharges. It follows from the foregoing that the most important function of prokaryotes in the biosphere is the involvement in the circulation of elements from inert (non-living) nature.
At the same time, prokaryotes also have another important function, directly opposite to the first one: the return of inorganic substances to the environment through the destruction (mineralization) of organic compounds. Heterotrophic bacteria function not only in soil and water, but also in the intestines of many animals, where they intensively affect the conversion of complex carbohydrate compounds into simpler forms.
At the level of the biosphere as a whole, prokaryotes, primarily bacteria, have another very important function - concentration. Research has established that microorganisms are able to actively extract certain elements from the environment even at extremely low concentrations. For example, in the waste products of some microorganisms, the content of iron, vanadium, manganese and a number of others is hundreds of times higher than in their environment. The activity of bacteria actually created natural deposits of these elements.
The properties and functions of prokaryotes are so diverse that, in principle, they are able to create stable functioning characteristic (that is, only with their participation) ecosystems. Not without reason, in the history of life on Earth for almost 2 billion years, it was represented by prokaryotes. "It was cyanobacteria that first populated the Bikini Atoll after a nuclear explosion and the island of Surrey, which arose in 1963 as a result of the eruption of an underwater volcano south of Iceland. High resistance to external influences (a number of species of prokaryotes withstand temperatures above 100 ° C, an acidic environment with a pH of with a content of 20-30% halite NaCl in solution) turns this group into representatives of living matter under the most extreme conditions" (Shilov I.A., 2000, p. 56)
It is the appearance of the eukaryotic cell that is one of the most significant events in biological evolution. The difference between eukaryotic and prokaryotic organisms is a more advanced system of genome regulation. And thanks to this, the adaptability of unicellular organisms has increased, their ability to adapt to changing environmental conditions without introducing hereditary changes into the genome. Thanks to the ability to adapt, eukaryotes were able to become multicellular - in a multicellular organism, cells with the same genome, depending on the conditions, form tissues that are completely different in morphology and function.
This aromorphosis occurred at the turn of the Archean and Proterozoic (2.6 - 2.7 billion years ago), which was determined by biomarkers - the remains of steroid compounds characteristic only of eukaryotic cells. The appearance of eukaryotes coincides in time with the oxygen revolution.
It is generally accepted that eukaryotes appeared as a result of symbiosis of several varieties of prokaryotes. Apparently, mitochondria originated from alpha-proteobacteria (aerobic eubacteria), plastids from cyanobacteria, and cytoplasm from an unknown archaebacterium. There is still no generally accepted theory of the origin of the nucleus, cytoskeleton, and flagella. Hypotheses of the origin of life on Earth did not clarify the question of the origin of the cell. If there are practically no hypotheses about the origin of prokaryotes that plausibly describe their origin, then regarding the origin of eukaryotic cells, there are several points of view.
The main hypotheses for the origin of eukaryotes:
1. Symbiotic hypothesis based on two concepts. According to the first of these concepts, the most fundamental distinction in living nature is the distinction between bacteria and organisms consisting of cells with true nuclei - protists, animals, fungi and plants. The second concept is that the source of some parts of eukaryotic cells was the evolution of symbioses - the formation of permanent associations between organisms of different species. It is assumed that three classes of organelles - mitochondria, cilia, and photosynthetic plastids - originated from free-living bacteria, which, as a result of symbiosis, were incorporated into the cells of prokaryotic hosts. This theory is largely based on neo-Darwinian ideas developed by geneticists, ecologists, cytologists, who connected Mendelian genetics with Darwin's idea of natural selection. It also draws on molecular biology, especially on the structure of proteins and the sequence of amino acids, on micropaleontology, which studies the earliest traces of life on Earth, and on the physics and chemistry of the atmosphere, since these sciences are related to gases of biological origin.
2.Invagination hypothesis says that the ancestral form of the eukaryotic cell was an aerobic prokaryote. Inside were several genomes attached to the cell membrane. Corpuscular organelles and the nucleus arose by invagination and lacing of sections of the membrane, followed by functional specialization into the nucleus, mitochondria, and chloroplasts. Then, in the process of evolution, the complication of the nuclear genome occurred and a system of cytoplasmic membranes appeared. This hypothesis explains the presence in the membranes of the nucleus, mitochondria, chloroplasts, and two membranes. But it encounters difficulties in explaining the differences in the details of the process of protein biosynthesis in the corpuscular organelles and the cytoplasm of the eukaryotic cell. In mitochondria and chloroplasts, this process exactly corresponds to that in modern prokaryotic cells.
The origin of the eukaryotic cell according to the symbiotic (I) and invagination (II) hypotheses:
1 - anaerobic prokaryote (host cell), 2 - prokaryotes with mitochondria, 3 - blue-green algae (presumptive chloroplast), 4 - syrochaete-like bacterium (presumptive flagellum), 5 - primitive eukaryote with a flagellum, 6 - plant cell, 7 - animal cell with a flagellum, 8 - aerobic prokaryote (presumptive mitochondrion), 9 - aerobic prokaryote (ancestor cell according to hypothesis II), 10 - invagination of the cell membrane, which gave the nucleus and mitochondria, 11 - primitive eukaryote 12 - invagination of the cell membrane, which gave chloroplast, 13 - plant cell; a - DNA of a prokaryotic cell, b - mitochondrion, c - nucleus of a eukaryotic cell, d - flagellum, e - chloroplast.
The available data are still insufficient to give preference to one of the hypotheses or develop a new one that would suit most scientists, but in recent years it has been possible to convincingly prove the symbiogenetic theory of the origin of the eukaryotic cell.
The evolutionary possibilities of eukaryotic type cells are higher than those of prokaryotic ones. The leading role here belongs to the eukaryotic nuclear genome, which is larger than the prokaryotic genome. Important differences are the diploidy of eukaryotic cells due to the presence of two sets of genes in the nuclei, as well as the multiple repetition of some genes.
The mechanism of regulation of cell vital activity becomes more complicated, which manifested itself in an increase in the relative number of regulatory genes, the replacement of circular “naked” DNA molecules of prokaryotes with chromosomes in which DNA is connected to proteins.
Aerobic respiration also served as a prerequisite for the development of multicellular forms. Eukaryotic cells themselves appeared on Earth after the concentration of O 2 in the atmosphere reached 1% (Pasteur's point). And this concentration is a necessary condition for aerobic respiration.
It is known that each eukaryotic cell contains genomes of different origin: in animal and fungal cells, these are the genomes of the nucleus and mitochondria, and in plant cells, they are also plastids. A small circular DNA is also found in the basal body of the flagella of eukaryotic cells.
According to the molecular clock method, eukaryotes arose at the same time as prokaryotes. But it is clear that for a significant part of the history of the Earth, it was dominated by prokaryotes. The first cells that correspond to eukaryotic sizes (acritarchs) are 3 billion years old, but their nature is still unclear. Almost certain remains of eukaryotes are about 2 billion years old. And only after the oxygen revolution on the surface of the planet did favorable conditions develop for eukaryotes (about 1 billion years ago).
Most likely, the main ancestor of eukaryotic cells was archaebacteria, which switched to nutrition by swallowing food particles. The change in cell shape required for this ingestion provided a cytoskeleton consisting of actin and myosin. The hereditary apparatus of such a cell has moved inward from its changeable surface, while retaining its connection with the membrane. And this already caused the appearance of a nuclear envelope with nuclear pores.
Absorbed by the host cell, the bacteria could continue their existence inside it. Thus, a group of photosynthetic bacteria, purple alphaproteobacteria, became the ancestors of mitochondria. Inside the host cell, they lost the ability to photosynthesis and took over the oxidation of organic substances. Thanks to them, eukaryotic cells became aerobic. Symbioses with other photosynthetic cells caused the acquisition of plastids by plant cells. It is possible that eukaryotic cell flagella evolved as a result of symbiosis of host cells with bacteria that were capable of wriggling movements.
The hereditary apparatus of eukaryotic cells was arranged approximately the same as in prokaryotes. But due to the need to control a larger and more complex cell, the organization of chromosomes later changed, and DNA was associated with histone proteins. The prokaryotic organization has been preserved in the genomes of intracellular symbionts.
As a result of various acts of symbiogenesis, various groups of eukaryotic organisms arose: eukaryotic cell + cyanobacteria = red algae; eukaryotic cell + prochlorophyte bacterium = green algae. Even the chloroplasts of golden, diatom, brown and cryptomonad algae arose as a result of two successive symbioses, as evidenced by the presence of 4 membranes in them.
The appearance of eukaryotes was timed to coincide with a period in the history of the biosphere, when conditions were especially unstable and unpredictable, when the adaptive strategy of prokaryotes (rapid mutation, horizontal gene exchange, and selection of resistant clones) turned out to be too wasteful and not effective enough. In such a situation, a fundamentally more universal and economical adaptive strategy based on the development of expedient modification variability could gain a great advantage.
Perhaps, the formation of eukaryotes and the development of their sexual process made the structure of variability and biodiversity more discrete and “manageable” – this should have led to an accelerated growth of biodiversity and to an increase in the evolutionary plasticity and ecological tolerance of species, communities and biota as a whole.
The appearance of eukaryotes can rightfully be called a "reference" aromorphosis. In this event, the general progressive direction of biological evolution was most clearly manifested. Progress was expressed not only in the complication of organization, the expansion of the total adaptive zone of life, the growth of biomass and abundance, the increase in the autonomy of organisms, but also in the increase in the stability of living systems.
Using the example of eukaryotes, it is clearly shown that the emergence of new forms of life should be considered not as a result of the evolution of some individual phyletic lineages or clades, but as a natural and inevitable effect of the development of higher-order systems - communities, the biosphere, and, possibly, the entire planet as a whole.
Sources used:
A. V. Markov, A. M. Kulikov. The origin of eukaryotes as a result of integration processes in the microbial community
A. V. Markov. The problem of the origin of eukaryotes
M. V. Larina. Hypotheses of the origin of eukaryotic cells. The emergence of multicellularity
Answer from Cat[guru]
Prokaryotes carry out photosynthesis differently than plants. Bacteria use the pigment bacteriochlorin in this process.
and do not release oxygen into the environment. Photoautotrophic archaebacteria carry out photosynthesis with the help of bacteriorhodopsin, and cyanobacteria, in addition to chlorophyll, additionally have two other pigments: phycocyanin and phycoerythrin. These facts show that nature has provided several pigments for the implementation of the synthesis of primary organic matter, which significantly expand the spectral composition of the radiation available for photosynthesis. Chemosynthesis is very common among prokaryotes. In addition, among bacterial organisms there are nitrogen-fixing forms: this is the only group of living organisms on our planet that are able to assimilate nitrogen directly from atmospheric air and thus involve molecular nitrogen in the biological cycle.
Bacteria and blue-greens include up to 90% of all nitrogen included in the biogenic cycle in the composition of organic matter; the remaining 10% of the nitrogen is bound by lightning electrical discharges. It follows from the foregoing that the most important function of prokaryotes in the biosphere is the involvement in the circulation of elements from inert (non-living) nature.
At the same time, prokaryotes also have another important function, directly opposite to the first one: the return of inorganic substances to the environment through the destruction (mineralization) of organic compounds. Heterotrophic bacteria function not only in soil and water, but also in the intestines of many animals, where they intensively affect the conversion of complex carbohydrate compounds into simpler forms.
At the level of the biosphere as a whole, prokaryotes, primarily bacteria, have another very important function - concentration. Research has established that microorganisms are able to actively extract certain elements from the environment even at extremely low concentrations. For example, in the waste products of some microorganisms, the content of iron, vanadium, manganese and a number of others is hundreds of times higher than in their environment. The activity of bacteria actually created natural deposits of these elements.
The properties and functions of prokaryotes are so diverse that, in principle, they are able to create stable functioning characteristic (that is, only with their participation) ecosystems. Not without reason, in the history of life on Earth for almost 2 billion years, it was represented by prokaryotes. "It was cyanobacteria that first populated Bikini Atoll after a nuclear explosion and the island of Surrey, which arose in 1963 as a result of an eruption of an underwater volcano south of Iceland. High resistance to external influences (a number of species of prokaryotes withstand temperatures above 100 ° C, an acidic environment with a pH of with a content of 20-30% halite NaCl in solution) turns this group into representatives of living matter under the most extreme conditions "(Shilov I. A., 2000, p. 56)
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The term " biosphere”was introduced into scientific literature at the end of the 19th century. geologist E. Suess to designate a special earthly shell inhabited by living organisms. A holistic doctrine of the biosphere was created in the first half of the 20th century. the largest naturalist-geochemist V. I. Vernadsky.
Based on an analysis of the history of atoms in the earth's crust and in its upper, engulfed by life, shell, Vernadsky came to conclusions of exceptional theoretical and, as it later became clear, practical significance. He showed that the biosphere is not only inhabited by living organisms, but also to a significant extent geochemically reworked by them; it is not only a living environment, but also a product of the vital activity of living organisms that have lived on earth at all geological times - the living substance of the planet. This provision, which is of exceptional importance for geochemistry, A. I. Perelman proposed to call the “Vernadsky law” and formulated it as follows: “The migration of chemical elements in the biosphere is carried out either with the direct participation of living matter (biogenic migration), or it proceeds in the environment , the geochemical features of which (O 2, CO 2, H 2 S, etc.) are due to living matter, both the one that currently inhabits this system and the one that acted in the biosphere during geological history "(Perelman , 1979, p. 215).
At an early stage in the development of biology, there was an idea that all life living on Earth is divided into two "kingdoms" of organisms: flora and fauna, or the plant kingdom - Plantae and the animal kingdom - Animalia. In the XVIII-XIX centuries. from the moment of discovery and subsequent intensive study of the world of microorganisms, it became necessary to distinguish a new third kingdom of living beings, called by Haeckel (1866) the kingdom of protists. The emergence of new branches of biology, in particular molecular biology, the improvement of microscopy techniques, the use of electron microscopy, the development of new modern methods for studying microorganisms, contributed to the further identification of new kingdoms of living nature; in modern classifications, five kingdoms are separated, united according to the type of cell structure into two groups (R. Murray, 1968; R. Whittaker, 1969):
animal kingdom - Animalia
Eukaryotes plant kingdom - Plantae
kingdom of protists - Protista
mushroom kingdom - Mycota
Prokaryotes bacterial kingdom - Procaryota
The prokaryotic type of microbial cell is characteristic of bacteria, actinomycetes and blue-green algae. Its main feature is the absence of a clear boundary between the nuclear substance and the cytoplasm and the absence of a nuclear membrane. The region of the nucleus (the so-called nucleoid) is filled with DNA that is not associated with a protein and does not form structures similar to eukaryotic chromosomes. There are also no mitochondria and chloroplasts, and the cell wall consists of a heteropolymeric substance, which is not found in any of the eukaryotic organisms. In the cytoplasm of photosynthetic bacteria there are thylakoids containing pigments (chlorophylls and carotenoids), with the help of which photosynthesis is carried out. In some types of bacteria, granules of fat and volutin accumulate in the cells.
The eukaryotic cell type is characteristic of fungi, algae, protozoa (similar to plant, animal and human cells). It is more complex: the nucleus with a two-layer nuclear porous membrane is separated from the cytoplasm, it contains one or two nucleoli, inside which RNA (ribonucleic acid) is synthesized and contains chromosomes - carriers of hereditary information, consisting of DNA and protein. In the cytoplasm there are also mitochondria (participating in the processes of respiration) and in algae chloroplasts (converting radiant energy into chemical energy).
According to absolute geochronology and paleontology, using the latest methods of biochemistry, life already existed in the Archaean 4-3.5 billion years ago. During deep reference drilling, set in the USSR on the Russian platform, many carbonaceous products of the transformation of the first photosynthetic organisms - blue-green algae and the smallest organic bodies of bacterial origin were found in the metamorphosed sedimentary rocks of the Archean. These prokaryotic organisms - bacteria and cyanophytes, which appeared in an oxygen-free atmosphere (but possessing a photosynthetic apparatus) - the only inhabitants of the Earth for more than 1 billion years, were the first producers of free oxygen in its atmosphere.
At the end of the Archean and the beginning of the Proterozoic - 2.6-2.2 billion years ago - the Earth's atmosphere already contained enough oxygen to carry out oxidative processes. Sulfates (products of sulfide oxidation) and lateritic bauxite-bearing formations containing Fe oxides have been found in rocks of this age (Sidorenko, Tenyakov, and others). Iron bacteria have been found in Proterozoic rocks aged 2 billion years (Zavarzin, 1972). Thus, already in the Archean and Lower Proterozoic, as a result of the gaseous and oxidizing functions of microorganisms, the sphere of the Earth inhabited by them was transformed to such an extent that it acquired the geochemical features of the modern biosphere.
The presence of free oxygen in the atmosphere has become a condition for the development of diverse forms of life - eukaryotic protozoa and multicellular plants and animals. The diagram of the evolution of the organic world, according to the ideas of the paleontologist Academician B.S. Sokolov, shows the main stages in the development of life not only in the Paleozoic and Mesozoic (which paleontology has been studying for a long time), but also in the Archaean, Aphebia (Middle and Lower Proterozoic) - a long period of the history of the Earth, when the simplest organisms dominated, and more complex ones appeared in the Riphean (Upper Proterozoic). The most ancient bacteria, blue-green algae (cyanophytes), fungi, protozoa, with the activity of which the formation of the biosphere is associated, have existed at all geological times and continue to exist today.
With the development and differentiation of life forms, all ecological niches of the biosphere were mastered, and their geochemical activity became more and more diverse. Along with gas and redox functions, the concentration functions of living organisms have acquired colossal planetary significance, especially pronounced in relation to C, Ca, Si.
The photosynthetic activity of organisms and the concentration of carbon and solar energy in the form of organic substances determined the global distribution of the formation of carbonaceous-siliceous and oil shale in the Proterozoic and Paleozoic. The development of marine fauna with a calcareous, phosphate, and siliceous skeleton in the Cambrian marked the beginning of the accumulation of thick suites of organogenic rocks, which continued in all subsequent geological epochs. The formation of these rocks is largely associated with the activity of microorganisms: lithified cells of cocolithophores are found in all calcareous sediments; accumulations of flint skeletons of diatoms and radiolarians form diatomites and tripoli.
A variety of geochemical functions of microorganisms, their high enzymatic activity significantly affect the geochemical processes of the modern biosphere.
The biosphere includes several geospheres: the troposphere, the hydrosphere (the World Ocean), the pedosphere and the upper part of the lithosphere - the crust and the weathering zone, the strata of sedimentary rocks up to the boundaries of the spread of life.
Living matter is unevenly distributed in the biosphere; places of the greatest concentration of living organisms and a variety of forms - soils, bottom sediments of lakes, tidal zones of sea coasts and shallow water shelves, the upper euphotic layer of the waters of the seas and oceans. As you move away from the surface of the Earth, the density of life and the diversity of species decrease. Life penetrates most deeply from the surface of the Earth in the World Ocean: the entire water column and the part of the bottom sediments accessible for observation are inhabited; at the bottom of the deepest oceanic trenches, such as the Mariana (11,022 m) and Philippine trenches (over 10,000 m) and others, there is a peculiar abyssal fauna, a diverse microflora.
On land, living cells of microorganisms were found in the thickness of the lithosphere at a shallower depth: when drilling wells in groundwater at 1500-2000 m, in oil-bearing waters at 4500 m. The penetration of organisms into the depths of the lithosphere is prevented by temperatures exceeding 100 ° C.
The upper limits of the biosphere, apparently, coincide with the boundary of the troposphere (11,000 m above sea level); it is possible for microorganisms to enter the stratosphere. However, active life at high absolute altitudes is limited not so much by low temperatures as by the lack of liquid water and carbon dioxide: the partial pressure of CO 2 at an altitude of 5600-5700 m is 2 times less than at sea level. Live, actively developing algae, fungi, bacteria are found in the mountains at altitudes of 6200-6500 m, where they are distributed not only on the rocks, but also on the surface and in the thickness of the firn and ice.
Consequently, microorganisms are settled within the entire biosphere and are indicators of its lower and upper boundaries: they develop in a wide range of environmental conditions, form colossal concentrations in places of general concentration of life, and fill ecological niches in extreme conditions where the life of higher organisms is impossible.
Such a wide distribution is facilitated, firstly, by the small mass and size of bacteria - 1-2 microns, yeast cells, fungal spores - about 10 microns. With water, they penetrate into the finest hairline cracks of rocks, reaching deep aquifers, rise to the upper boundaries of the troposphere, carried away by air currents, fly into the stratosphere, make global movements and inhabit the glaciers of Greenland and Antarctica.
Microorganisms are very hardy, tolerate severe desiccation and do not lose viability, living cells contain 80-85% water. Dried spores of mold fungi, some bacilli, containing only 40% water, retain the ability to germinate for 10-20 years. Non-spore-bearing, microorganisms withstand drying for several months.
In the dried state, microorganisms are resistant to direct sunlight and high temperatures, so abundant microflora lives on the surface of soils, rocks and rock fragments in deserts.
The vast majority of microorganisms tolerate low temperatures well. Experiments carried out in laboratories (Becquerel, 1925) showed that bacterial and fungal spores kept for half a year or more at liquid air temperature (-190°C) did not die and retained the ability to germinate. When pumping air, in a rarefied atmosphere, they withstood even lower temperatures. Evidence of the endurance of microorganisms to low temperatures is their wide distribution in the nival belt of mountains, polar regions, permafrost horizons of soils and soils. Many microorganisms are able to go into a state of anabiosis under adverse conditions. At the slightest improvement in the external environment, they return to life: the assimilation of water, carbon dioxide begins, rapid reproduction, for example, the division of micrococci occurs every half hour. In places where life is concentrated, millions and billions of cells of various microorganisms inhabit every cubic centimeter of natural waters, soils and bottom sediments.
The ubiquitous distribution of microorganisms, the high speed of life cycles, along with the variety of functions performed, determine their exceptional role in the geochemical processes of the biosphere. The study of the geochemical functions of living matter in the biosphere is the main task of biogeochemistry, founded by V. I. Vernadsky; its intensive development began in the middle of the 20th century, when, in connection with the ever-increasing technogenic activity of mankind, the problems of environmental protection arose.
All geochemical functions of microorganisms in the biosphere can be divided into the following types with a certain degree of conventionality:
1) assimilation - in relation to the gases of the atmosphere and the creation of organic matter;
2) destructive - in relation to organic matter;
3) gas - regulation of the gas regime of soils, water bodies, surface atmosphere;
4) redox - in relation to macro - and microelements with variable valency;
5) destructive - in relation to rocks and minerals;
6) accumulative functions and the creation of biogenic minerals and rocks.
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