What would happen if there were no microorganisms in the world?

Without microorganisms, plants can't metabolize, and humans and animals can't survive.

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Microorganisms refer to those biological groups whose individual volume and diameter are generally less than 65438±0mm, and their structures are simple, mostly single cells, and some even have no cell structure. People usually use microscopes or electron microscopes to see their shapes and structures clearly. It should be noted that microorganism is a relatively general concept, and the boundaries are sometimes very vague. For example, unicellular algae and some protozoa should also be considered microorganisms, but they are usually not studied in microorganisms.

According to the classification proposed by Chinese scholars, organisms are divided into six kingdoms: virus kingdom, monera kingdom, protozoa kingdom, fungi kingdom, plant kingdom and animal kingdom. It is not difficult to see that microorganisms occupy four of the six realms, so the important position of microorganisms in nature is obvious, and its research objects are also very extensive and rich.

Microbiology is a general term for a group of microorganisms that are widely present in nature and invisible to the naked eye, and can only be observed by magnifying hundreds, thousands or even tens of thousands of times with the help of optical microscope or electron microscope. They have the advantages of small size, simple structure, fast reproduction, easy variation and strong adaptability to the environment.

There are many kinds of microorganisms, at least more than100000. According to their differences in structure, chemical composition and living habits, they can be divided into three categories.

1. Eukaryotic microorganisms have a high degree of nuclear differentiation, including nuclear membranes, nucleoli and chromosomes; There are complete organelles (such as endoplasmic reticulum, ribosome and mitochondria) in cytoplasm. Fungi belong to this kind of microorganisms.

Second, the degree of nuclear differentiation of prokaryotic microorganisms is low, with only primitive nucleoplasm, no nuclear membrane and nucleoli; The organelles are not perfect. There are many kinds of such microorganisms, including bacteria, spirochetes, mycoplasma, rickettsia, chlamydia and actinomycetes.

3. Cell-free microorganisms have no typical cell structure and no enzyme system to produce energy, and can only grow and reproduce in living cells. Viruses belong to this type of microorganism.

Microorganisms are widely distributed in nature, and there are different kinds of microorganisms in air, soil, rivers, lakes and oceans. There are also many kinds of microorganisms on the body surfaces of human beings, animals and plants and their cavities communicating with the outside world.

Most microorganisms are beneficial and necessary for the survival of human beings, animals and plants. The circulation of nitrogen, carbon, sulfur and other elements in nature depends on the metabolic activities of microorganisms. For example, a large amount of nitrogen in the air can only be absorbed by plants under the action of microorganisms, while microorganisms in the soil can transform the protein of plants and animals into inorganic nitrogen-containing compounds to meet the needs of plant growth, and plants are used by humans and animals. Therefore, without microorganisms, plants cannot be metabolized, and humans and animals cannot survive.

In agriculture, human beings make extensive use of the characteristics of some microorganisms, and use bacteria to fertilize, promote growth, prevent diseases and treat diseases, thus opening up a new way to increase agricultural production. In industry, microorganisms are widely used in food, tanning, textile, petroleum, chemical industry and other fields. Especially in the pharmaceutical industry, almost all antibiotics are metabolites of microorganisms, and microorganisms can also be used to make some drugs such as vitamins and coenzymes.

Even many microorganisms parasitic in human and animal body cavities are harmless under normal circumstances, and some of them also have the function of resisting the invasion and settlement of foreign bacteria and providing necessary nutrients (such as vitamins and amino acids) for human beings.

A few microorganisms can cause diseases of human beings, animals and plants. These pathogenic microorganisms are called pathogenic microorganisms. Some microorganisms are not pathogenic under normal circumstances, but can cause diseases under certain conditions, which are called conditionally pathogenic microorganisms.

Microbiology is a branch of biology, which studies the evolution and classification of microorganisms, the morphology, structure and life activities of microorganisms under certain conditions, and the relationship between microorganisms and human beings, sports, plants and nature. With the expansion and deepening of research scope, microbiology has gradually formed many branches, mainly focusing on general microbiology, microbial taxonomy, microbial physiology, microbial ecology, microbial genetics, molecular microbiology and so on. According to the research object, it can be divided into bacteriology, mycology and virology. According to the research and application fields, it can be divided into agricultural microbiology, industrial microbiology, medical microbiology, veterinary microbiology, food microbiology, marine microbiology, soil microbiology and so on.

Medical microbiology and its development history

Medical microbiology is a branch of microbiology and a basic subject of medicine. This paper mainly studies the morphology, structure, metabolic activity, inheritance and variation, pathogenic mechanism, anti-infection immunity, laboratory diagnosis and specific prevention of pathogenic microorganisms related to human diseases. The purpose of studying medical microbiology is to understand the biological characteristics and pathogenicity of pathogenic microorganisms; Understand the immune function of human body to pathogenic microorganisms, the relationship between infection and immunity and its law; Understand the laboratory diagnosis methods and prevention principles of infectious diseases. Mastering the basic theory, knowledge and skills of medical microbiology can lay a foundation for the study of basic medicine and clinical medicine and help to control and eliminate infectious diseases.

Medical microbiology is a science summarized by human beings in the process of long-term understanding of the pathogenic nature of infectious diseases and disease prevention and treatment. Understanding the past, present and future of medical microbiology is helpful for us to sum up the laws, find the correct research direction and preventive methods, and further develop medical microbiology.

First, the experience period of microbiology.

Although ancient humans have not observed microorganisms, they have applied the knowledge of microbiology to industrial and agricultural production and disease prevention. In the Xia and Yu dynasties more than 2000 years BC, there was a record of wine-making in Yidi. In the Northern Wei Dynasty (AD 386-534), Qi Yaomin recorded the method of making vinegar in detail. For a long time, the common methods of preserving food, such as pickling, adding sugar, smoking and air drying, actually prevent food from rotting and deteriorating by inhibiting the growth of microorganisms.

Regarding the occurrence and prevalence of infectious diseases, 1 1 At the beginning of the century, Liu Zhenren proposed that tuberculosis was caused by insects at the end of the Northern Song Dynasty in China. Italy's fracastoro (1483 ~1553) thinks that infectious diseases can spread directly, indirectly and through the air. Plenciz, Austria (1705 ~1786) thinks that the cause of infectious diseases is living body, and each infectious disease is caused by a unique living body. /kloc-During the Qianlong period of the Qing Dynasty in the 0/8th century, Mr. Daonan of our country vividly described the tragic situation of plague epidemic at that time in the book "The Day of Fools" and correctly pointed out the relationship between plague and rats.

In preventive medicine, China has the habit of boiling water since ancient times. In the Ming Dynasty, Li Shizhen pointed out in Compendium of Materia Medica that steaming patients' clothes before wearing will not infect diseases, which indicates that disinfection has been recorded. A large number of ancient books proved that human pox was widely used to prevent smallpox in Qin Long during the Ming Dynasty (1567 ~ 1572), and it first spread to Russia, Korea, Japan, Turkey, Britain and other countries, which was a great contribution of preventive medicine in China.

Second, the period of experimental microbiology

The discovery of microorganisms was first observed by Antali van Leeuwenhoek (1632 ~ 1723). 1676, he made the world's first microscope with self-grinding lens (magnification is about 40 ~ 270 times), and observed and described various forms of microorganisms from rainwater, pond water and other specimens for the first time, which provided strong evidence for the existence of microorganisms and laid the foundation for the establishment of microbial morphology.

During the period of 65438+1960s, the wine industry and silk industry, which occupied an important economic position in some European countries, suffered from alcohol deterioration and silkworm diseases, which promoted people's research on microorganisms. French scientist louis pasteur (1822 ~ 1895) first proved that the fermentation and corruption of organic matter were caused by microorganisms. The deterioration of alcohol is due to the pollution of miscellaneous bacteria, which overthrew the popular theory of spontaneous occurrence at that time. Pasteur's research initiated the physiological era of microorganisms. People realize that there are not only differences in morphology but also differences in physiological characteristics among different microorganisms, which further affirms the important role that microorganisms play in nature. Since then, microbiology has become an independent discipline.

Pasteur invented the disinfection method of heating to prevent alcohol from deteriorating, which is the pasteurization method still used in alcohol and milk. Under the influence of Pasteur, British surgeon joseph lister (1827 ~ 19 12) pioneered the use of carbolic acid to spray operating rooms and boil surgical instruments, which laid the foundation for anticorrosion, disinfection and aseptic operation.

Another founder of microbiology is German scholar Koch (1843 ~ 19 10). He created a solid culture medium, which can separate the bacteria in samples such as environment or patient's excrement into a single colony, which is convenient for studying various bacteria separately. At the same time, dyeing method and experimental animal infection provide favorable conditions for finding pathogens of various infectious diseases. /kloc-in the last 20 years of the 0/9th century, most pathogens of bacterial infectious diseases were discovered, isolated and cultivated by Koch and a large number of scholars led by him.

Russian scholar Dmitri Iosifovich Ivanovsky (Nвановски) discovered the first virus-tobacco mosaic virus in 1892. 1897 FMDV was found in animals in Raffler and Frosch. 190 1 year, American scholar Walter Reid first isolated the yellow fever virus that caused human diseases. 19 15 bacterial virus (phage) was discovered by British scholar Twater. Later, many viruses from humans, animals and plants were isolated.

The rise of immunology1At the end of 8, edward jenner (1749 ~ 1823) pioneered the use of vaccinia to prevent smallpox; Subsequently, Pasteur successfully developed vaccines for chicken cholera, carbon jaundice and rabies, which opened up a road for immunology and preventive medicine. People's understanding of the nature of anti-infection immunity began at the end of 19. German scholar Behring successfully cured a diphtheria child with animal immune serum containing diphtheria antitoxin in 189 1, which attracted the attention of scientists looking for bactericidal substances from serum and promoted the development of serology. Due to the different research fields and emphases, there are two different academic views on the explanation of anti-infective immunity: the humoral immunology school represented by Poulehrlich (1854 ~1916) thinks that the immunity of the body is related to bactericidal substances in blood and other body fluids, mainly the function of specific antibodies; However, the school of cellular immunology represented by Mechnikov (m. ечниовии.), 1845 ~ 19 16) thinks that the function of phagocytosis is Soon, Wright found opsonin in serum, and proved that the function of phagocytes can be greatly enhanced with the participation of humoral factors, and the two immune factors complement each other, thus making people have a more comprehensive understanding of immune mechanism and promoting the further development of immunology.

The invention of chemotherapeutic drugs and antibiotics was that ehrlich first synthesized chemotherapeutic drugs. He synthesized arsenic vanadyl amine for treating syphilis at 19 10, and then synthesized a new arsenic vanadyl amine, which pioneered the way of chemotherapy for microbial diseases. Later, a series of sulfonamides were synthesized, which were widely used in the treatment of infectious diseases. Fleming first discovered that penicillin produced by Penicillium can inhibit the growth of Staphylococcus aureus in 1929, but it was not until 1940 that Florey purified the Penicillium culture solution that pure penicillin was obtained and used to treat infectious diseases, which achieved amazing results. The discovery and application of penicillin greatly encouraged microbiologists, and then antibiotics such as streptomycin, chloramphenicol, chlortetracycline, oxytetracycline, tetracycline and erythromycin were continuously discovered and widely used in clinic.

Third, the period of modern microbiology.

In recent decades, due to the development of biochemistry, genetics, cell biology, molecular biology and other disciplines, as well as the progress of electron microscope, gas phase, liquid chromatography, immunology, monoclonal antibody technology and molecular biology technology, the development of medical microbiology has been promoted. People can explore the gene structure and function, pathogenic substance basis and diagnostic methods of pathogenic microorganisms at the molecular level, so that people can have a deeper understanding of the activity law of pathogenic microorganisms. Some new pathogenic microorganisms have been discovered one after another, such as Legionella, Campylobacter, Lassa fever virus, Marburg virus and human immunodeficiency virus.

1967 ~ 197 1 year, American plant virologist Diener and others found that the pathogen of potato spindle tuber disease is a protein-free RNA with a molecular weight of about 100000. This pathogenic factor is called viroid. Later, in the process of studying viroid, a virus causing alfalfa and other plant diseases was discovered. 1982 found that the pathogen causing sheep itch is a protein with molecular weight of 27KD, which is called prion. 1983 these pathogenic factors are collectively referred to as viruses in relevant international conferences. Subviruses may also exist in humans, such as Creutzfeldt-Jakob disease and Kuru disease, which may be caused by prions or prions.

In recent ten years, the rapid detection and diagnosis methods of pathogenic microorganisms have developed rapidly. Enzyme-linked immunosorbent assay (ELISA) has been widely used to detect antigens and antibodies, which simplifies the complicated microbial testing procedures in the past, especially the use of monoclonal antibodies, and further improves the specificity and sensitivity of detection. At present, many diagnostic kits have been prepared, among which the wide application of virus rapid diagnosis kit has made the rapid laboratory diagnosis of viral diseases difficult to realize for a long time in the past a reality. At present, many laboratories are exploring the application of gene probe and polymerase chain reaction (PCR) in the rapid detection of microorganisms.

In the prevention of infectious diseases, most pathogenic microorganisms that seriously endanger human health have developed corresponding vaccines. 1980, the world health organization announced the global eradication of smallpox, which is the first serious infectious disease completely eliminated by human beings, and the most fundamental measure is universal vaccination. Extensive inoculation of various vaccines has become the most effective and economical means for human beings to deal with various infectious diseases.

In the treatment of infectious diseases, new antibiotics are constantly produced, which effectively controls the epidemic of bacterial infectious diseases. In contrast, the research progress of antiviral drugs is slow. In recent years, the application of cytokines (such as interleukin -2, interferon, etc. ) to treat some viral diseases, and achieved certain results. In addition, the application of monoclonal antibodies and gene therapy in the treatment of viral diseases is increasingly extensive and in-depth.

From 65438 to 0957, Australian scholar Burnet. F.M. is based on the work of his predecessors and his own research. The famous cell line selection theory was put forward, which made immunology enter a new field of biomedicine. Especially in the last two decades, immunology has developed very rapidly, involving many aspects of biology such as cell biology, molecular biology, molecular genetics and clinical disciplines, far exceeding the traditional concept of infectious immunity in the past, and has become one of the most important basic disciplines in medicine and biology independently.

Although mankind has made great achievements in the field of medical microbiology and infectious disease control, the pathogens of some infectious diseases are still not fully understood, and some diseases still lack effective prevention and treatment methods. Therefore, medical microbiology should strengthen the research on the biological characteristics and pathogenicity of pathogenic microorganisms in the future, and establish specific rapid early diagnosis methods; Develop new vaccines, improve the original vaccines, and improve the control effect. It is necessary to strengthen the research on infection immunity, and look for or artificially synthesize nonspecific and specific substances that can mobilize and improve the body's defense function. In order to strengthen the research of genetic engineering, we should not only make preparations for diagnosis, prevention, treatment and research, but also take gene therapy for some genetic diseases related to microbial infection to completely cure such diseases. We should continue to strengthen contact and cooperation with immunology, biochemistry, genetics, cell biology, histology, pathology and other disciplines, and adopt advanced technology, especially molecular biology technology. Only in this way can we accelerate the development of medical microbiology and contribute to the early control and elimination of various infectious diseases that endanger human health.

Xu zhikai

In nature, there is a large class of people whose tiny lives are invisible to the naked eye. Whether it is a bustling modern city, a rich and vast field, a rare mountain peak or a vast ocean, there are traces of them everywhere. These tiny "residents" are called microbes, and together with animals and plants, they form a biological army, which makes nature look full of vitality. The microbial kingdom is a real "lilliputian country", where the "subjects" belong to several representative families, such as bacteria, actinomycetes, fungi, viruses, viroids, rickettsia, chlamydia and mycoplasma. These families have surprisingly few members. Take the "big man" Bacillus of the bacterial family as an example. Let 3000 bacilli "lie" in a row end to end, only the size of a grain of rice. Let 70 bacilli arrange side by side, as wide as a hair; The total population of the whole earth (more than 5 billion) adds up to the number of bacteria, only the weight of a sesame seed. Microorganisms are so small that people can only measure them in microns or even smaller units. As we all know, 1 micron is equal to 1‰ mm, and the size of bacteria is generally only a few microns, and some are only 0. 1 micron, while the human eye has only a resolution of about 0.06 mm. No wonder we can't see it. How are microorganisms discovered? Interesting to say. 300 years ago, there was a man named Levin Hook in Holland. Although he doesn't read much, he loves science and is full of the spirit of assiduous study. He is also good at grinding magnifying glasses. He made a simple microscope, and his polished lens can magnify the original object more than 200 times. One day, Leeuwenhoek took some crumbs from an old man's teeth to observe, and unexpectedly found countless little guys with different shapes jumping around there. He was so surprised that he could hardly believe his eyes. Levin Hook described the shapes of these little guys in detail. He said, "There are more' small animals' in this old man's mouth than the residents of the whole Kingdom of the Netherlands ..." After that, he continued to observe the stagnant water in various containers, as well as rivers, wells and sewage, and found that there was such a "small animal" world suitable for all living things. Levin Hooke was the first to see bacteria through a microscope, which opened the door for human beings to understand microorganisms. Since then, people have unveiled the mystery of microorganisms with the help of a microscope.

Of course, you can also see microorganisms. For example, edible fungi, medicinal ganoderma lucidum and puffball are all microorganisms. Biologists once discovered a kind of huge mushroom in former Czechoslovakia, which belongs to fungi. Can you guess how big it is? -Its diameter is over 4m and its weight is over100kg. It is not only a "giant" in the microbial family, but also a "nobody" in the whole biological world.

The miracle of microbial kingdom

Microorganisms are the earliest "inhabitants" on the earth. If the history of the earth's evolution to today is condensed into one day, and the birth of the earth is zero within 24 hours, then the first inhabitants of the earth-anaerobic heterotrophic bacteria were born at 7 am; At about 13 in the afternoon, aerobic heterotrophic bacteria appeared; Fish and terrestrial plants are produced at 22 o'clock at night; And humans will not appear until the last moment of the day. Microorganisms can first appear on the earth and continue to this day, which is related to their unique large appetite, wide recipes, rapid reproduction and strong resistance. The smaller the appetite, the greater the appetite, which is a universal law of biology. The structure of microorganisms is very simple. A cell or a simple cell group is an organism that can live independently and assume all the functions of life activities. Although they are very small, their whole body surface has the function of absorbing nutrients, which makes their "appetite" extremely huge. If the sugar consumed by a bacterium in one hour is converted into the food that a person wants to eat, then this person will eat for 500 years. Microorganisms not only eat a lot, but also eat everything. All organic and inorganic substances on the earth are insatiable, and even the most novel and complex organic molecules synthesized by chemists cannot escape the "mouth" of microorganisms. People call those microorganisms that only "eat" ready-made organic matter organic nutrition or heterotrophic microorganisms; Other microorganisms that rely on carbon dioxide and carbonate to maintain themselves are called inorganic nutrients or autotrophic microorganisms. Microorganisms are divided into male and female, and their reproduction methods are different. As far as members of the bacterial family are concerned, they reproduce through their own division. As long as the conditions are right, it can be divided once every 20 minutes, divided into two, divided into four, divided into eight and so on. If calculated at this rate, a bacterium can produce 2.2e43 offspring in 24 hours, with a total weight of 2.2e28, which is equivalent to the weight of four earths!

Although the reproduction of this geometric series is often limited by the environment, food and other conditions, it is actually impossible to achieve, even so, it is enough for animals and plants to lag behind. Microorganisms have strong heat resistance, cold resistance, salt resistance, drying resistance, acid resistance, alkali resistance, hypoxia resistance, pressure resistance, radiation resistance and poison resistance. Therefore, from the bottom of the Pacific Ocean with a depth of 65438+100000 meters and a water pressure as high as 1 140 atmospheric pressure to the atmosphere with a height of 85000 meters; From hot equatorial waters to cold Antarctic glaciers; Traces of microorganisms can be found from the dead sea with high salinity to the environment with strong acid and alkali. Because microorganisms are only afraid of "open flames", except for active craters, the whole earth is their territory. Of course, microorganisms have to breathe, but some like to take oxygen, which is aerobic; There are anaerobic, anaerobic; Others can survive in aerobic and anaerobic environments and are called facultative microorganisms. Microorganisms can not only eat but also sleep. It is reported that there are still living bacteria on the mummies of three or four thousand years ago in the Egyptian pyramids. The dormancy ability of microorganisms is also amazing.

Dominant bacteria

Since the German country doctor robert koch first discovered bacteria, the name of bacteria has often been associated with diseases. Because many infectious diseases of people and animals and plants are caused by bacteria, people always have a feeling of disgust and fear. In fact, the bacteria that harm human beings are only a small part. Most bacteria can not only live in peace with us, but also benefit mankind. For example, a large number of animals and plants die on the earth every year. Thousands of years have passed. Where did the remains of these animals and plants go? This is due to bacteria and other microorganisms. They can eat all the remains of all living things on the earth, and at the same time convert them into nutrients that plants can use, making great contributions to promoting the material cycle in nature. Moreover, many bacteria play an important role in industrial and agricultural production! Under the microscope, the bacteria we see have roughly three shapes: chubby and round, called cocci; The elongated body is Bacillus; The body is twisted and deformed, which is called spirillum. No matter what shape it is, it is just a single cell, and its internal structure is similar to that of an ordinary plant cell. It has a tough and elastic "shell" called cell wall, which bacteria rely on to protect their bodies. Near the cell wall, there is a flexible membrane called cell membrane, which is the "gateway" for food and waste to enter and leave the cell. The cell membrane is filled with viscous colloidal solution, which is cytoplasm, containing various particles and storage substances. Some bacteria have nuclei, but they are much simpler than large organisms, so people call them prokaryotic cells. Most bacteria can't move, but because they are small and light, they can travel around the world with the help of wind, water or dust and birds and animals attached to the air. Some bacteria have flagella, like the tail of a fish. They can crawl in the water, and bacteria can swim at a very fast speed. It is observed that Vibrio cholerae can fly within 1 hour 18cm with the swing of flagella, which is equivalent to 90000 times its length! Among bacteria, some are "naked" naked; Some people wear a special kind of "clothes", which is a loose layer of mucus around the cell wall, called capsule. It is not only a food storage for bacteria, but also a "armor" for protection. Capsule is also closely related to pathogenicity for bacteria. For example, pneumococcus can cause pneumonia, but if it loses its capsule, it will be disarmed and not pathogenic. When bacteria encounter harsh environments such as dryness, high temperature, lack of oxygen or chemical substances, they can also use a unique trick, that is, almost all the water in the body is removed, so that the cells condense into oval dormant bodies, which are spores. Spores still have vitality for decades under dry conditions. Once the environment becomes suitable, spores will absorb water and swell, and become viable cells again. A single bacterium is colorless and transparent, so it is necessary to color it for easy identification. 1884, Danish scientist Gram created a double dyeing method, that is, first dyeing with crystal violet solution and iodine solution, then decoloring with alcohol, and then dyeing with dilute red solution. After such treatment, bacteria can be divided into two categories, those that can be dyed purple are called gram-positive bacteria; Anything dyed red is called gram-negative bacteria. There are great differences in life habits and cell composition between these two bacteria. Doctors often choose drugs to diagnose and treat diseases according to the Gram stain of bacteria. In memory of Gram, double staining is also called Gram staining. Members of the bacterial family, if they grow and reproduce in a fixed place, form a small group visible to the naked eye, which is called colony. Colonies are colorful, such as Pseudomonas aeruginosa colony is green, staphylococcus colony is golden yellow. The shape, size, thickness and color of bacterial colonies are one of the basis for identifying various strains. Fleming is pouring cakes through observation? Sodium earthworm? ⑾? Quot Eating penicillin without staphylococci has uncovered the secret of antibiotics in an epoch-making way.

Actinomycetes with many utilization values

Doctors often use antibiotics such as streptomycin and erythromycin to treat diseases, which makes many patients turn to safety. The protagonist of antibiotics is a famous actinomycete. Actinomycetes consist of one cell, which is very similar to bacteria, so it is often regarded as an independent family in the bacterial family. However, actinomycetes has many characteristics of fungi, such as the thallus is composed of many septate mycelium, so it is a transitional type between bacteria and fungi from the perspective of biological evolution. Actinomycetes have many tiny entangled thalli called hyphae. These hyphae have different division of labor, and some of them "eat with their heads buried", which are substrate hyphae specialized in absorbing nutrients; Some grow violently into the sky, which is an aerial mycelium, as a symbol of the growth and development of actinomycetes. Actinomycetes begin to "give birth" at a certain stage. They first grow spore filaments at the top of aerial hyphae and divide into strings of spores after maturity. Some spores are like balls, others are like eggs, which can be scattered with the wind. When they meet the right environment, they will "settle down" there, start to absorb water and sprout new actinomycetes. Actinomycetes are abundant in soil. Most of them are saprophytic bacteria, which can rot and "eat" the light of plants and animals, and then convert it into nutrients conducive to plant growth, thus making immortal contributions to the natural material cycle. There is also a kind of Frankliniella, which grows in the root nodules of many non-leguminous plants and can fix nitrogen in the atmosphere and become a nitrogen fertilizer that plants can use. Actinomycetes have made many contributions. More than half of the thousands of antibiotics found at present are produced by actinomycetes. Its colony is brightly colored and radial, which is harmless to human body. Therefore, people often use it as a coloring agent for food, which is both beautiful and safe. Actinomycetes can also be used to produce medical supplies, such as vitamin B 12, protease and glucose isomerase. Although some kinds of actinomycetes are harmful to human beings, such as mycobacteria can cause tuberculosis and leprosy, these achievements are really insignificant compared with actinomycetes.

A large family of fungi.

Fungi are the largest family in the microbial kingdom, with more than 250,000 members. The name auricularia auricula sounds strange, but you often come into contact with it in your life. For example, delicious mushrooms, nutritious tremella, auricularia auricula, Ganoderma lucidum for prolonging life, Poria cocos for promoting diuresis and relieving swelling, and Cordyceps sinensis for protecting lung and kidney, stopping bleeding and resolving phlegm are all members of the fungus family. Brewing wine, mixing flour and making soy sauce are all inseparable from the help of yeast or mold, and they are outstanding representatives of the fungal family. Judging from the process of biological evolution, the birth of fungi is about 65.438 billion years later than that of bacteria, so it is the youngest family in the microbial kingdom. The most fundamental difference between them and bacteria and actinomycetes is that fungi already have real nuclei. Therefore, people call fungal cells eukaryotic cells. The development from prokaryotic cells to eukaryotic cells is a major event in the history of biological evolution. Fungi have a multicellular structure and can produce spores for sexual and asexual reproduction. Although mushrooms and Hericium erinaceus are tall and big, they look like plants, but they have no cellulose and chloroplasts in their cell walls, so they can't produce chlorophyll like plants, which is an important difference between them and plants. Fungi are an important source of human food, many of which are precious Chinese herbal medicines. Fungi can also produce a variety of antibiotics. Fungi not only play an important role in traditional brewing and food industry, but also play an important role in modern industry. People use different molds to prepare various enzyme preparations and many important industrial raw materials and reagents, which can also be used as efficient feed to develop aquaculture. However, fungi can also bring a lot of harm to human beings. During the rainy season, white "hair" will grow on furniture and clothes; In damp warehouses, food, vegetables and fruits often rot and deteriorate; Many people are infected with onychomycosis and various tinea diseases. , are caused by fungi. /kloc-in the summer of 0/960, more than 65,438+10,000 turkeys died inexplicably somewhere in England. At that time, no one could tell what disease it was, and it was called "Turkey X disease". Later, it was discovered that these turkeys ate moldy peanut cakes, which contained a toxin produced by Aspergillus flavus called aflatoxin. This is a strong carcinogen, which can cause liver cancer in many animals and has a certain correlation with human liver cancer. Therefore, our basic attitude towards fungi is to recognize enemies as friends, foster strengths and avoid weaknesses, and let them make greater contributions to mankind.

Evil virus

Viruses are much smaller than bacteria and can only be seen with an electron microscope that can magnify objects millions of times. The average virus is only one tenth of the diameter of a hair. Viruses are much simpler than bacteria. The whole body consists of nucleic acid and protein shell, and there is no cell wall. Protein's shell determines the shape of the virus. Some of them are rod-shaped and linear, some are like balls, duck eggs, shells, and some are like tadpoles. Viruses cannot live alone, but must live a parasitic life in living cells, so the cells of various organisms have become the "home" of viruses. Viruses parasitic on humans or other animals are called animal viruses, such as human smallpox, hepatitis and influenza.