Harmful and beneficial bacteria
Bacteria are microorganisms that form a huge invisible world around and inside us. Because of their harmful effects they have a bad reputation, while the beneficial effects they cause are rarely talked about. This article gives general description some bad and good bacteria.
“During the first half of geological time, our ancestors were bacteria. Most creatures are still bacteria, and each of our trillions of cells is a colony of bacteria." - Richard Dawkins.
Bacteria- the most ancient living organisms on Earth are omnipresent. The human body, the air we breathe, the surfaces we touch, the food we eat, the plants around us, our environment, etc. - all this is inhabited by bacteria.
Approximately 99% of these bacteria are beneficial, while the rest have a bad reputation. In fact, some bacteria are very important for the proper development of other living organisms. They can exist either on their own or in symbiosis with animals and plants.
The following list of harmful and beneficial bacteria includes some of the most well-known beneficial and deadly bacteria.
Lactic acid bacteria/Dederlein rods
Characteristic: gram-positive, rod-shaped.
Habitat: Varieties of lactic acid bacteria are present in milk and dairy products, fermented foods, and are also part of the oral, intestinal, and vaginal microflora. The most predominant species are L. acidophilus, L. reuteri, L. plantarum, etc.
Benefit: Lactic acid bacteria are known for their ability to use lactose and produce lactic acid as by-product life activity. This ability to ferment lactose makes lactic acid bacteria an important ingredient in the preparation of fermented foods. They are also an integral part of the brining process, as lactic acid can serve as a preservative. Through what is called fermentation, yogurt is obtained from milk. Certain strains are even used to make yoghurts in industrial scale. In mammals, lactic acid bacteria help break down lactose during the digestive process. The resulting acidic environment prevents the growth of other bacteria in the body's tissues. Therefore, lactic acid bacteria are an important component of probiotic preparations.
Bifidobacteria
Characteristic: gram-positive, branched, rod-shaped.
Habitat: Bifidobacteria are present in gastrointestinal tract person.
Benefit: Like lactic acid bacteria, bifidobacteria also produce lactic acid. In addition they produce acetic acid. This acid inhibits the growth of pathogenic bacteria by controlling the pH level in the intestines. The bacterium B. longum, a species of bifidobacteria, helps break down difficult-to-digest plant polymers. B. longum and B. infantis bacteria help prevent diarrhea, candidiasis, and even fungal infections in infants and children. Due to these beneficial properties, they are also often included in probiotic preparations sold in pharmacies.
Escherichia coli (E. coli)
Characteristic:
Habitat: E. coli is part of the normal microflora of the large and small intestines.
Benefit: E. coli helps in breaking down undigested monosaccharides, thus aiding digestion. This bacterium produces vitamin K and biotin, which are essential for various cellular processes.
Note: Certain strains of E. coli can cause serious toxic effects, diarrhea, anemia, and kidney failure.
Streptomycetes
Characteristic: gram-positive, filamentous.
Habitat: These bacteria are present in soil, water and decaying organic matter.
Benefit: Certain streptomycetes (Streptomyces spp.) play an important role in soil ecology by decomposing organic matter present in it. For this reason, they are being studied as a bioremediation agent. S. aureofaciens, S. rimosus, S. griseus, S. erythraeus and S. venezuelae are commercially important species that are used to produce antibacterial and antifungal compounds.
Mycorrhizae/Nodule bacteria
Characteristic:
Habitat: Mycorrhizae are present in the soil, existing in symbiosis with the root nodules of leguminous plants.
Benefit: Bacteria Rhizobium etli, Bradyrhizobium spp., Azorhizobium spp. and many other varieties are useful for fixing atmospheric nitrogen, including ammonia. This process makes this substance available to plants. Plants do not have the ability to use atmospheric nitrogen and depend on nitrogen-fixing bacteria present in the soil.
Cyanobacteria
Characteristic: gram-negative, rod-shaped.
Habitat: Cyanobacteria are primarily aquatic bacteria, but they are also found on bare rocks and in soil.
Benefit: Cyanobacteria, also known as blue-green algae, are a group of bacteria that are very important for environment. They fix nitrogen in the aquatic environment. Their calcification and decalcification abilities make them important for maintaining balance in the coral reef ecosystem.
Harmful bacteria
Mycobacteria
Characteristic: are neither gram-positive nor gram-negative (due to high content lipids), rod-shaped.
Diseases: Mycobacteria are pathogens that have a long doubling time. M. tuberculosis and M. leprae, their most dangerous varieties, are the causative agents of tuberculosis and leprosy, respectively. M. ulcerans causes ulcerated and non-ulcerated nodules on the skin. M. bovis can cause tuberculosis in livestock.
Tetanus bacillus
Characteristic:
Habitat: Tetanus bacillus spores are found in the soil, on the skin, and in the digestive tract.
Diseases: Tetanus bacillus is the causative agent of tetanus. It enters the body through a wound, multiplies there and releases toxins, particularly tetanospasmin (also known as a spasmogenic toxin) and tetanolysin. This leads to muscle spasms and respiratory failure.
Plague stick
Characteristic: gram-negative, rod-shaped.
Habitat: The plague bacillus can survive only in the body of the host, in particular in the body of rodents (fleas) and mammals.
Diseases: The plague bacillus causes bubonic plague and plague pneumonia. Skin infection caused by this bacterium takes on a bubonic form, characterized by malaise, fever, chills and even convulsions. An infection of the lungs caused by bubonic plague causes plague pneumonia, which causes coughing, difficulty breathing and fever. According to WHO, between 1,000 and 3,000 cases of plague occur worldwide each year. The plague pathogen is recognized and studied as a potential biological weapon.
Helicobacter pylori
Characteristic: gram-negative, rod-shaped.
Habitat: Helicobacter pylori colonizes the human gastric mucosa.
Diseases: This bacterium is the main cause of gastritis and peptic ulcers. It produces cytotoxins and ammonia that damage the gastric epithelium, causing abdominal pain, nausea, vomiting and bloating. Helicobacter pylori is present in half the world's population, but most people remain asymptomatic, and only a few develop gastritis and ulcers.
Anthrax bacillus
Characteristic: gram-positive, rod-shaped.
Habitat: Anthrax bacillus is widespread in the soil.
Diseases: Anthrax infection results in a fatal disease called anthrax. Infection occurs as a result of inhalation of endospores of anthrax bacillus. Anthrax mainly occurs in sheep, goats, cattle, etc. However, in rare cases, transmission of the bacterium from livestock to humans occurs. The most common symptoms of anthrax are ulcers, fever, headache, abdominal pain, nausea, diarrhea, etc.
We are surrounded by bacteria, some of them harmful, others beneficial. And it depends only on us how effectively we coexist with these tiny living organisms. It is up to us to benefit from beneficial bacteria by avoiding excessive and inappropriate use of antibiotics, and to stay away from harmful bacteria by taking appropriate steps. preventive measures, such as maintaining personal hygiene and undergoing routine medical examinations.
They surround us everywhere. Many of them are very necessary and useful for humans, but many, on the contrary, cause terrible diseases.
Do you know what forms bacteria come in? How do they reproduce? What do they eat? Do you want to know?
.site) will help you find in this article.
Shapes and sizes of bacteria
Most bacteria are single-celled organisms. They come in a wide variety of shapes. Bacteria are given names depending on their shape. For example, round-shaped bacteria are called cocci (well-known streptococci and staphylococci), rod-shaped bacteria are called bacilli, pseudomonads or clostridia (bacteria of this shape include the famous tuberculosis bacillus or Koch's wand). Can bacteria have the shape of spirals, then their names spirochetes, vibrils or spirilla. Not so often, but bacteria in the shape of stars, various polygons or other geometric shapes do occur.Bacteria are not at all large, their sizes range from half to five micrometers. The largest bacterium measures seven hundred and fifty micrometers. After the discovery of nanobacteria, it turned out that their size is much smaller than scientists previously imagined. However, to date, nanobacteria have not been well studied. Some scientists even doubt their existence.
Aggregates and multicellular organisms
Bacteria can attach to each other using mucus, forming cellular aggregates. Moreover, each individual bacterium is a self-sufficient organism, the vital activity of which does not depend in any way on its relatives glued to it. Sometimes it happens that bacteria stick together in order to perform some common function. Some bacteria, usually filamentous, can also form multicellular organisms.How do they move?
There are bacteria that are not able to move on their own, but there are also those that are equipped with special devices for movement. Some bacteria move using flagella, while others can glide. How bacteria glide is not yet fully understood. It is believed that bacteria secrete a special mucus that makes sliding easier. There are also bacteria that can “dive”. In order to descend into the depths of any liquid medium, such a microorganism can change its density. In order for a bacterium to move in any direction, it must receive irritation.Nutrition
There are bacteria that can only feed organic compounds, and there are those that can process inorganics into organics and after that use them for their own needs. Bacteria obtain energy in three ways: using respiration, fermentation or photosynthesis.Reproduction
Regarding the proliferation of bacteria, we can say that it is also not uniform. There are bacteria that do not divide into sexes and multiply simple division or budding. Some cyanobacteria have the ability to multiple divisions, that is, in one go they can produce up to a thousand “newborn” bacteria. There are also bacteria that reproduce sexually. Of course, they do all this very primitively. But at the same time, two bacteria transfer their genetic data to the new cell - this is the main feature of sexual reproduction.Bacteria undoubtedly deserve your attention not only because they cause many diseases. These microorganisms were the first living beings to inhabit our planet. The history of bacteria on Earth goes back almost four billion years! The most ancient cyanobacteria existing today are cyanobacteria; they appeared three and a half billion years ago.
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Many types of bacteria are useful and are successfully used by humans.
Firstly, beneficial bacteria are widely used in Food Industry.
In the production of cheeses, kefir, and cream, it is necessary to coagulate milk, which occurs under the influence of lactic acid. Lactic acid is produced by lactic acid bacteria, which are part of starter cultures and feed on the sugar contained in milk. Lactic acid itself promotes the absorption of iron, calcium, and phosphorus. These beneficial elements help us fight infectious diseases.
When making cheese, it is pressed into pieces (heads). The cheese heads are sent to ripening chambers, where the activity of the various lactic acid and propionic acid bacteria that make up the cheese begins. As a result of their activity, the cheese “ripens” - acquires a characteristic taste, smell, pattern and color.
To produce kefir, a starter containing lactic acid bacilli and lactic acid streptococci is used.
Yogurt is a tasty and healthy fermented milk product. Milk for yoghurt production must be very High Quality. It should contain a minimum amount of harmful bacteria that can interfere with the development of beneficial yogurt bacteria. Yogurt bacteria convert milk into yogurt and give it its distinctive flavor.
Rice. 14. Lactobacilli – lactic acid bacteria.
Lactic acid and yoghurt bacteria entering the human body with food help fight not only harmful bacteria in the intestines, but also by viruses – the causative agents of colds and other infections. In the process of their life activity, these beneficial bacteria create such an acidic environment (due to the excreted metabolic products) that only a microbe very adapted to difficult conditions, such as E. coli, can survive next to them.
The activity of beneficial bacteria is used in the fermentation of cabbage and other vegetables.
Secondly, bacteria are used to leach ores in the extraction of copper, zinc, nickel, uranium and other metals from natural ores. Leaching is the extraction of minerals from ore that is not rich in them using bacteria, when other methods of extraction (for example, smelting ore) are ineffective and expensive. Leaching is carried out aerobic bacteria.
Third, beneficial aerobic bacteria are used to treat urban wastewater and industrial enterprises from organic remains.
The main goal of such biological treatment is the neutralization of complex and insoluble organic substances waste water, which cannot be extracted from it mechanical cleaning, and their decomposition to simple water-soluble elements.
Fourth, bacteria are used in the production of silk and leather processing, etc. The raw materials for the production of artificial silk are produced by special transgenic bacteria. Technical lactic acid bacteria are used in the tanning industry for swelling and deashing (processing raw materials from solid compounds), in the textile industry, as aid for dyeing and printing.
Fifth, bacteria are used to control agricultural pests. Agricultural plants are treated with special preparations that contain certain types of bacteria. Insect pests, consuming parts of plants treated with biological preparations, ingest bacterial spores with food. This leads to the death of pests.
Sixth, bacteria are used to produce various medications (for example, interferon) that kill viruses and support human immunity (defense).
And lastly, harmful bacteria also have beneficial properties.
Decay bacteria (coprophytic bacteria) destroy the corpses of dead animals, leaves of trees and shrubs that have fallen to the ground, and the trunks of dead trees themselves. These bacteria are a kind of orderlies for our planet. They feed organic substances and turn them into humus - fertile layer land.
Soil bacteria live in the soil and also provide many benefits in nature. Mineral salts produced by soil bacteria are then absorbed from the soil by plant roots. One cubic centimeter of the surface layer of forest soil contains hundreds of millions of soil bacteria.
Rice. 15. Clostridia are soil bacteria.
Bacteria also live in the soil and absorb nitrogen from the air, accumulating it in their bodies. This nitrogen is then converted into proteins. After the bacterial cells die, these proteins are converted into nitrogenous compounds (nitrates), which act as fertilizer and are well absorbed by plants.
Conclusion.
Bacteria are a large, well-studied group of microorganisms. Bacteria are found everywhere and people encounter them in their lives all the time. Bacteria can be beneficial to humans, or they can become a source of dangerous diseases.
Studying the properties of bacteria, combating their harmful manifestations and using useful properties The vital activity of bacteria is one of the main tasks for humans.
Student of 6th grade B _________________________________ / Yaroslav Shchipanov /
Literature.
1. Berkinblit M.B., Glagolev S.M., Maleeva Yu.V., Biology: Textbook for grade 6. – M.: Binom. Knowledge Laboratory, 2008.
2. Ivchenko, T. V. Electronic textbook “Biology: 6th grade. Living organism". // Biology at school. - 2007.
3. Pasechnik V.V. Biology. 6th grade Bacteria, fungi, plants: Textbook. for general education textbook establishments, - 4th ed., stereotype. – M.: Bustard, 2000.
4. Smelova, V.G. Digital microscope in biology lessons // Publishing House “First of September” Biology. - 2012. - No. 1.
Bacteria- one of the most ancient organisms on Earth. Despite the simplicity of their structure, they live in all possible habitats. Most of them are found in the soil (up to several billion bacterial cells per 1 gram of soil). There are many bacteria in the air, water, food, inside and on the bodies of living organisms. Bacteria have been found in places where other organisms cannot live (on glaciers, in volcanoes).
Typically a bacterium is a single cell (although there are colonial forms). Moreover, this cell is very small (from fractions of a micron to several tens of microns). But main feature A bacterial cell is the absence of a cell nucleus. In other words, bacteria belong prokaryotes.
Bacteria are either mobile or immobile. In the case of non-motile forms, movement is carried out using flagella. There may be several of them, or there may be only one.
Cells different types bacteria can differ greatly in shape. There are spherical bacteria ( cocci), rod-shaped ( bacilli), similar to a comma ( vibrios), crimped ( spirochetes, spirilla) and etc.
Structure of a bacterial cell
Many bacterial cells have mucous capsule. It performs a protective function. In particular, it protects the cell from drying out.
Like plant cells, bacterial cells have cell wall. However, unlike plants, its structure and chemical composition somewhat different. The cell wall is made up of layers complex carbohydrate. Its structure is such that it allows various substances to penetrate into the cell.
Under the cell wall is cytoplasmic membranenA.
Bacteria are classified as prokaryotes because their cells do not have a formed nucleus. They do not have the chromosomes characteristic of eukaryotic cells. The chromosome contains not only DNA, but also protein. In bacteria, their chromosome consists only of DNA and is a circular molecule. This genetic apparatus of bacteria is called nucleoid. The nucleoid is located directly in the cytoplasm, usually in the center of the cell.
Bacteria do not have true mitochondria and a number of other cellular organelles (Golgi complex, endoplasmic reticulum). Their functions are performed by invaginations of the cell cytoplasmic membrane. Such invaginations are called mesosomes.
In the cytoplasm there is ribosomes, as well as various organic inclusion: proteins, carbohydrates (glycogen), fats. Bacterial cells may also contain various pigments. Depending on the presence or absence of certain pigments, bacteria can be colorless, green, or purple.
Nutrition of bacteria
Bacteria arose at the dawn of life on Earth. They were the ones who “discovered” various ways nutrition. Only later, with the complication of organisms, two large kingdoms clearly emerged: Plants and Animals. They differ from each other primarily in the way they feed. Plants are autotrophs, and animals are heterotrophs. Bacteria have both types of nutrition.
Nutrition is the way a cell or body obtains the necessary organic substances. They can be obtained from outside or synthesized independently from inorganic substances.
Autotrophic bacteria
Autotrophic bacteria synthesize organic substances from inorganic ones. The synthesis process requires energy. Depending on where autotrophic bacteria receive this energy from, they are divided into photosynthetic and chemosynthetic.
Photosynthetic bacteria use the energy of the Sun, capturing its radiation. In this they are similar to plants. However, while plants release oxygen during photosynthesis, most photosynthetic bacteria do not release it. That is, bacterial photosynthesis is anaerobic. Also, the green pigment of bacteria differs from the similar pigment of plants and is called bacteriochlorophyll. Bacteria do not have chloroplasts. Mostly photosynthetic bacteria live in bodies of water (fresh and salty).
Chemosynthetic bacteria For the synthesis of organic substances from inorganic ones, the energy of various chemical reactions. Energy is not released in all reactions, but only in exothermic ones. Some of these reactions take place in bacterial cells. So in nitrifying bacteria the oxidation of ammonia into nitrites and nitrates occurs. Iron bacteria oxidize ferrous iron into oxide iron. Hydrogen bacteria oxidize hydrogen molecules.
Heterotrophic bacteria
Heterotrophic bacteria are not capable of synthesizing organic substances from inorganic ones. Therefore, we are forced to obtain them from the environment.
Bacteria that feed on the organic remains of other organisms (including dead bodies) are called saprophyte bacteria. They are otherwise called rotting bacteria. There are many such bacteria in the soil, where they decompose humus into inorganic substances, which are subsequently used by plants. Lactic acid bacteria feed on sugars, converting them into lactic acid. Butyric acid bacteria decompose organic acids, carbohydrates, and alcohols to butyric acid.
Nodule bacteria live in the roots of plants and feed on the organic matter of the living plant. However, they fix nitrogen from the air and provide it to the plant. That is, in this case there is a symbiosis. Other heterotrophic symbiont bacteria live in the digestive system of animals, helping to digest food.
During the process of respiration, organic substances are destroyed and energy is released. This energy is subsequently spent on various processes vital activity (for example, movement).
An effective way to obtain energy is oxygen respiration. However, some bacteria can obtain energy without oxygen. Thus, there are aerobic and anaerobic bacteria.
Aerobic bacteria oxygen is needed, so they live in places where it is available. Oxygen is involved in the oxidation reaction of organic substances to carbon dioxide and water. In the process of such respiration, bacteria receive a relatively large amount of energy. This method of breathing is characteristic of the vast majority of organisms.
Anaerobic bacteria They do not need oxygen to breathe, so they can live in an oxygen-free environment. They receive energy from fermentation reactions. This method oxidation is ineffective.
Bacteria reproduction
In most cases, bacteria reproduce by dividing their cells in two. Before this, the circular DNA molecule doubles. Each daughter cell receives one of these molecules and is therefore a genetic copy of the mother cell (clone). Thus, it is typical for bacteria asexual reproduction.
Under favorable conditions (with sufficient nutrients and favorable environmental conditions), bacterial cells divide very quickly. So from one bacterium hundreds of millions of cells can form per day.
Although bacteria reproduce asexually, in some cases they exhibit the so-called sexual process, which flows in the form conjugation. During conjugation, two different bacterial cells come closer and a connection is established between their cytoplasms. Parts of the DNA of one cell are transferred to the second, and parts of the DNA of the second cell are transferred to the first. Thus, during the sexual process, bacteria exchange genetic information. Sometimes bacteria exchange not sections of DNA, but entire DNA molecules.
Bacterial spores
The vast majority of bacteria form spores under unfavorable conditions. Bacterial spores are mainly a way of surviving unfavorable conditions and a method of dispersal, rather than a method of reproduction.
When a spore is formed, the cytoplasm of the bacterial cell contracts, and the cell itself is covered with a dense, thick protective membrane.
Bacterial spores remain viable for a long time and are able to survive very favorable conditions(extremely tall and low temperatures, drying).
When a spore finds itself in favorable conditions, it swells. After this, the protective shell is shed, and an ordinary bacterial cell appears. It happens that cell division occurs and several bacteria are formed. That is, sporulation is combined with reproduction.
The importance of bacteria
The role of bacteria in the cycle of substances in nature is enormous. This primarily applies to rotting bacteria (saprophytes). They are called nature's orderlies. By decomposing the remains of plants and animals, bacteria convert complex organic substances into simple inorganic substances (carbon dioxide, water, ammonia, hydrogen sulfide).
Bacteria increase soil fertility by enriching it with nitrogen. Nitrifying bacteria undergo reactions during which nitrites are formed from ammonia, and nitrates from nitrites. Nodule bacteria are able to assimilate atmospheric nitrogen, synthesizing nitrogen compounds. They live in the roots of plants, forming nodules. Thanks to these bacteria, plants receive the nitrogen compounds they need. Basically, leguminous plants enter into symbiosis with nodule bacteria. After they die, the soil is enriched with nitrogen. This is often used in agriculture.
In the stomach of ruminants, bacteria break down cellulose, which promotes more efficient digestion.
The positive role of bacteria in the food industry is great. Many types of bacteria are used to produce lactic acid products, butter and cheese, pickling vegetables, as well as in winemaking.
In the chemical industry, bacteria are used to produce alcohols, acetone, and acetic acid.
In medicine, bacteria are used to produce a number of antibiotics, enzymes, hormones and vitamins.
However, bacteria can also cause harm. They not only spoil food, but with their secretions they make it poisonous.
Bacteria are microorganisms consisting of just one cell. Feature bacteria - lack of a clearly defined nucleus. That is why they are called “prokaryotes,” which means nuclear-free.
Currently, science knows about ten thousand species of bacteria, but there is an assumption that there are more than a million species of bacteria on earth. Bacteria are believed to be the most ancient organisms on Earth. They live almost everywhere - in water, soil, atmosphere and inside other organisms.
Appearance
Bacteria are very small and can only be seen with a microscope. The shape of bacteria is quite diverse. The most common forms are in the form of sticks, balls and spirals.
Rod-shaped bacteria are called "bacilli".
Bacteria in the form of balls are cocci.
Bacteria in the form of spirals are spirilla.
The shape of the bacterium determines its mobility and ability to attach to a particular surface.
Structure of bacteria
Bacteria have a fairly simple structure. These organisms have several main structures - nucleoid, cytoplasm, membrane and cell wall, in addition, many bacteria have flagella on the surface.
Nucleoid- This is something like a nucleus; it contains the genetic material of the bacterium. It consists of only one chromosome, which looks like a ring.
Cytoplasm surrounds the nucleoid. The cytoplasm contains important structures - ribosomes, necessary for bacteria to synthesize protein.
Membrane, covering the cytoplasm from the outside, plays an important role in the life of the bacterium. It delimits the internal contents of the bacterium from external environment and ensures the exchange processes between the cell and the environment.
The outside of the membrane is surrounded cell wall.
The number of flagella may vary. Depending on the species, one bacterium has from one to a thousand flagella, but there are bacteria without them. Bacteria need flagella to move through space.
Nutrition of bacteria
Bacteria have two types of nutrition. One part of bacteria is autotrophs, and the other is heterotrophs.
Autotrophs create themselves nutrients through chemical reactions, and heterotrophs feed on organic substances that other organisms have created.
Bacteria reproduction
Bacteria reproduce by division. Before the division process, the chromosome located inside the bacterium doubles. Then the cell divides in two. The result is two identical daughter cells, each of which receives a copy of the mother's chromosome.
The importance of bacteria
Bacteria play a vital role in the cycle of substances in nature - they convert organic residues into inorganic substances. If there were no bacteria, then the entire earth would be covered with fallen trees, fallen leaves and dead animals.
Bacteria play a dual role in human life. Some bacteria are of great benefit, while others cause significant harm.
Many bacteria are pathogenic and cause various diseases, for example, such as diphtheria, typhus, plague, tuberculosis, cholera and others.
However, there are bacteria that benefit people. This is how bacteria live in the human digestive system, which contribute to normal digestion. And lactic acid bacteria have long been used by people to produce lactic acid products - cheeses, yogurt, kefir, etc. Bacteria also play an important role in the fermentation of vegetables and the production of vinegar.
Bacteria brief information.
