The evolution of microorganisms

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Introduction

The geological record of the planet - the remains of extinct creatures - irrefutable proof that life on the planet has changed: some animal and plant species disappeared, others appeared, modify, creating new forms. The same, but on a smaller scale can be seen in isolated islands or other closed areas: a few thousands or even hundreds of years of isolation such animals and plants have markedly different from living on the other side of the water, or other obstacles.

Historical changes of hereditary traits of organisms called evolution (from the Latin. Evolutio - «deploy»). This process has three very important consequences. Firstly, in the course of evolution, there are new types, i.e. increasing the diversity of organisms. Secondly, the body adapts to changes in ambient conditions; therefore say that evolution is adaptive in nature. Finally, thirdly, as a result of evolution gradually increased the overall level of the organization of living beings: they become more complex and refined.

planet bacteria parasitism

In those days - more than four billion years ago - is still very young, our planet has little resemblance to the present: the surface temperature was very high (up to 8000 degrees Celsius), all the terms of the planet rock - melted. Even the diameter of the Earth was less than now, and the full rotation around its axis she performed for eighteen hours and not twenty-four, as it is now. The planet's surface is continuously bombarded by meteorites, including a very large (several hundred kilometers in diameter!). The bigger they are, the more it heats the Earth's crust.

When ended the era of the "great bombardment", the Earth began to cool gradually. Rocks that form the planet, becomes hard and form an uneven surface. When the temperature dropped below a hundred degrees Celsius, the water, the former before the ferry was shed on the earth by rain and filled the troughs. Thus arose the primeval ocean. The atmosphere of that time, too, is strikingly different from today: its main components are ammonia, methane, hydrogen and water vapor. The atmosphere is almost did not detain the sun's rays, especially ultraviolet, harmful to living organisms.

As in such conditions could harbor life?

In 1923, Russian scientist Alexander Oparin suggested that in the primitive Earth organic matter arose from the simplest compounds - ammonia, methane, hydrogen and water. The energy required for such conversions could be obtained, or UV, or by frequent electrical discharges of lightning - lightning. Perhaps these organic substances are gradually accumulated in the ancient ocean, forming the "primordial soup" in which life began.

According to the hypothesis A.I.Oparina in the "primordial soup" long threadlike protein molecules can fold into balls, "stick together" with each other, enlarged. Because of this, they became resistant to the damaging effects of ultraviolet radiation and surf. Protein "balls" in the "primordial soup" to attract and bound water molecules, as well as fat. Fat deposited on the surface of proteins, enveloping their bed structure that remotely resembles the cell membrane. This process is called the Oparin coacervation (from the Latin. Coacervus - «clot»), and the resulting body - coacervate drops, or just coacervates. Over time coacervates absorbed from the surrounding solution of all the new portions of the substance, their structure is complicated, as long as they do not become very primitive, but in living cells.

The ancient atmosphere had no oxygen. Therefore, the first single-celled organisms like bacteria to date, was used as the oxidant for the process of respiration and energy source of iron ions and other chemical elements. Moreover, the oxygen would have been fatal to these ancient beings appeared, he immediately would have destroyed their cells. However, about 3.5 billion years ago there was the first revolution. Cells some primitive beings have acquired the ability to use the energy of sunlight, i.e., photosynthesize, producing organic matter from inorganic. They probably resembled modern blue-green algae. At the same time these unusual organisms have been providing oxygen into the atmosphere. The first living creature to escape the poisonous gas for them, have disappeared from the planet's surface and from the upper layers of water in lakes and seas, preserved only in the depths of geological rocks, where they were protected by a layer of minerals.

The ancient blue-green algae have completely changed the Earth: oxygen-rich atmosphere is expelled from the surface of primitive bacteria, but made it possible to further improve the other forms, from whom all modern organisms. However, this was still far off, because the improvement of the living creatures went very slowly.

The second (after the occurrence of photosynthesis) revolution occurred around 2,5mlrd years ago, along with the prokaryotic bacteria and cyan bacteria algae appeared eukaryotic single-celled organism. Scientists believe that they are descended from prokaryotes. The main difference between eukaryotic cells - that it contains intracellular membranes.

They probably originated in ancient bacterial cells due to the invagination inside their shells. These bubbles have become digestive vacuoles, liposomes and cisterns of the endoplasmic reticulum. This acquisition gave the ancient organism's distinct advantage: they are less dependent on the environment, as the stockpiling of food inside the cells.

Such a body could already go to feed the bacteria and blue-green algae, grabbing their cell membrane protrusions and imprisoned in digestive vacuoles formed, then to digest. Perhaps this "predator" was so greedy that did not immediately digest "swallowed" the victim and kept them for some time inside their unicellular body.

Was captured bacteria and unicellular blue-green algae learned how to multiply inside a large cage predator, and eventually even made peace with him, based on mutual benefit: bacteria evolved into the mitochondria, providing the host cell with energy, and blue-green algae - in the plastids (chloroplasts and chromoplasts), and began to carry out photosynthesis and some other duties.

Third Revolution occurred about 1.2 billion years ago, when there was a sexual reproduction. As a result of sharply increased exchange of hereditary material between organisms and as a result increased their diversity, creates the preconditions for further improvement of life.

A typical representative of a living organism that time was for collar flagellate - a creature that combines features of modern flagellates and amoebae. Perhaps this organism lived, attach to the bottom of the ocean or sea. You can also imagine how this creation fed. Fluctuating water flagellum directed through openings collar (outgrowth checkered wall in the form of an annular plate). Water-fit small particles of food, and they settled on the collar, on the strainer. These particles are captured is used to power the device - pseudopodium. The flagellate cell formed digestive vacuole in which it was digesting particles - just as it does with amoebas.

In the future, single - celled organisms living together and joined, forming a colony. In such a colony by repeated cell division becomes crowded. Organism's neighbors interfere with each other to produce the necessary food. To cope with the problem of helping specialization: some single-celled retain only collars and flagella, some, on the contrary, lose their flagella, but retain the false foot. If different cell colonies united in stable layers. Each such layer or fabric has a specific function. So begins the evolution of multicellular organisms.

Parasitism, as well as other forms of relationships between parasites and their hosts, originated, developed and improved in the evolution of organisms. It is believed that free-living bacteria-saprophytes appeared over 3 billion. Years ago during the origin of life on our planet, and micro-parasites much later - as education eukaryotes.

The basis of parasitism are expanding and updating the environmental value of saprophytes because before them opened up new spheres of environmental distribution. So, any elective (optional) parasites, many of which, without causing significant damage to the host organism is recovered for the benefit of themselves. This form of interspecies relationship called commensalism. It is characteristic of the putrefaction of saprophytic microorganisms that have mastered a new ecological niche - the intestines of animals and humans. They are opportunistic, or opportunistic, types of bacteria (Escherichia, Proteus, etc.), Yeast like fungi populations which in normal conditions are without prejudice to the owner. However, in extreme cases these organisms cause disease processes.

With increasing dependence on the host organism there was a further improvement of parasitism, which led to the emergence of pathogenic - infectious diseases of humans and animals. Many of them lost their saprophytic form in its development as opposed to opportunistic pathogens. They have not been able not only to reproduce, but even persist in the environment.

So, treponema of syphilis, whooping cough and other bacteria. Survive in the environment only a few minutes, Enter bacteria - a few weeks or months, etc. However, spore-forming pathogens (anthrax) and conditionally pathogenic bacteria (Clostridium tetanus and gas gangrene) persist for months and years in the form of spores.

As the parasites depending on the host organism appeared facultative intracellular parasites. These include gonococci and meningococcal, tubercle bacilli, Shigella and other bacteria that can multiply in human cells. These views have not lost the ability to reproduce in artificial media, indicating preservation of their set of enzymes required for anabolic kataba-and-crystal reactions. In the later stages of evolution appeared obligate intracellular parasites, which include Chlamydia, Rickets pathogenic protozoa. These pathogens preserved cellular organization, but lost the genes that control the formation of a number of enzymes required for essential metabolic reactions so that they have lost the ability to grow on nutrient media.

Thus, as a result of a regressive evolution appeared obligate intracellular parasites with reduced metabolic reactions, totally dependent on his master. As in the extracellular and intracellular parasites have overwhelming number of which refers to pathogenic species during evolution appeared factors, protect them from and nonspecific immune defense of the host.

The main driving force behind the evolution of microbial parasitism, during which formed pathogenic species were mutation and recombination of genes. As a result, directional selection of individuals most adapted to the specific conditions in the human body, there was improvement of virulent pathogens and toxic properties of the formation of their new varieties and species.

Basic factors selective directional selection operating in humans and animals and are non-specific immune defense of the host, as well as ever-increasing arsenal of chemotherapeutic etiotropic and immune (vaccines, immunoglobulin's) preparations.

The number of new genotypes, survivors of directional selection is in direct proportion to the number of existing selective factors. This leads to a constant renewal of the gene pool of the microbial population. Of particular importance in the evolution of pathogens plays a constant migration information extra chromosomal factors of heredity, or transposable element (transpose's, plasmids). As already noted, they control the formation of a wide variety of products: toxins, enzymes, antigens, which in certain cases give selective advantages pathogen cells bearing them.

This raises the question of the origin and role of transposable elements in the evolution of pathogens. Most likely, the transposable element occurred due to chromosomal genes that acquired the ability to segregate from the bacterial DNA.

This is evidenced by the fact that the chromosomal genes are usually responsible for the formation of the same pathogen factors that are controlled by transposable elements. In the autonomous state in the past, there are circular form that can be incorporated back into the bacterial chromosome. This often occurs at the site of integration of the insert Zion mutation due to the shift of reading.

Germs can affect the evolutionary development of the host.

Conclusion

Thus, the evolutionary role of extra chromosomal factors of heredity is to increase the heterogeneity of the bacterial populations, which ultimately contributes to the survival of the biomass with altered antigens and pathogens that are best adapted to these specific conditions of existence in the body of his master. It is now established similarities between the provirus and transposable elements. About viruses represent a form of viral DNA, which is integrated into the chromosome of the host cell. Above this form of interaction between the virus and the cell it was described as integrative infection.

In this regard, it may be assumed that DNA viruses derived from transposable elements bacterial cells which, when excision of the bacterial chromosome can acquire structural genes controlling the formation of the viral caused, and corresponding regulatory genes.

However, widespread reverse transcription among viruses, bacteria, yeast, plants, insects, vertebrates and man is one of the arguments in favor of the hypothesis of the initial formation of RNA.

Literature

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