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Purpose of the study: study the characteristics of the life activity of bacteria; Learn about diseases caused by bacteria and their prevention.
- study the available literature on this issue;
- analyze the effect of pathogenic bacteria on the human body;
- obtain and summarize information from an infectious disease specialist at Rospotrebnadzor about bacterial diseases in our area and their prevention.
Research methods:
- study of literature;
- collection of information;
- analysis of collected information and systematization;
- presentation of results.
Progress of the lesson
Introduction.
In 5th grade we started studying a new subject - biology. I was interested in the chapter “The Kingdom of Bacteria” and had questions:
Why are bacteria, relatively simple microscopic single-celled organisms, so viable?
What conditions contribute to the spread of pathogenic bacteria and what preventive measures exist?
Theoretical part
The bacteria were first seen under an optical microscope and described by the Dutch naturalist Antonie van Leeuwenhoek in 1676. Like all microscopic creatures, he called them “animalcules.”
The name “bacteria” was coined by Christian Ehrenberg in 1828.
Louis Pasteur in the 1850s initiated the study of the physiology and metabolism of bacteria, and also discovered their pathogenic properties.
Medical microbiology was further developed in the works of Robert Koch, who formulated the general principles for determining the causative agent of a disease (Koch's postulates). In 1905 he was awarded the Nobel Prize for his research on tuberculosis.
The study of the structure of a bacterial cell began with the invention of the electron microscope in the 30s of the 20th century.
The bacterial body consists of a single cell. This cell is structured completely differently than the cells of plants, animals and fungi. If their cells are separated by numerous partitions (membranes) into special compartments where the processes of respiration, nutrition, photosynthesis, etc. are carried out, then in bacteria the “partitioning” is in the most rudimentary stage. The most important difference is that the bacterium lacks a nucleus. Another difference is that there are no mitochondria and plastids. DNA in bacteria is located in the center of the cell, coiled into a chromosome. If you “unwind” the bacterial DNA, its length will be about 1 mm.
Under favorable conditions, bacterial cells multiply very quickly, dividing in two. If a cell doubles every half hour, then it can give birth to offspring within a day. And some bacteria can multiply even faster.
And another interesting ability of bacteria. In unfavorable conditions they can often turn into spores. Such disputes remain alive for tens and hundreds of years, and in exceptional cases, even millions of years.
These features of bacteria allow them to survive in any conditions.
Depending on the shape of the cells, bacteria are divided into several groups: spherical - cocci, rod-shaped - bacilli or rods, spiral - spirilla, in the form of a comma – vibrios.
Human diseases caused by bacteria
Bacterial diseases are one of the most common human diseases. Such diseases include some pneumonia (caused by streptococcus), anthrax (caused by Bacillus anthrax), cholera (caused by Vibrio cholerae), tuberculosis (caused by the tubercle bacillus (Koch bacillus), plague (caused by the plague bacillus) and others.
In ancient times and in the Middle Ages, this disease was called “Black Death,” which instilled panic in people. In the VI century. The plague epidemic killed 100 million people. Some states, such as the Byzantine Empire, were almost completely depopulated.
From 1346 to 1351, the plague (“the great pestilence”, as they said then) killed 24 million people - a quarter of the population of then Europe. The Italian Renaissance writer Giovanni Boccaccio begins his book “The Decameron” with a story about the plague epidemic in 1348: “At the beginning of the disease, some tumors appeared under the arms of men and women, growing to the size of an ordinary apple or egg; the people called them buboes. In a short time, this deadly tumor spread to other parts of the body, and then the sign of the said disease changed into black and purple spots that appeared on all parts of the body. It seemed that neither the doctor’s advice nor the power of the medicine helped or brought any benefit against this disease... neither the wisdom nor the foresight of man helped against it. Almost everyone died on the third day after the appearance of these symptoms.”
In the 20th century Plague epidemics practically ceased to threaten humans. Why did this happen? Of course, the systematic fight against this disease played a role. The black rat, whose fleas served as carriers of the disease, has almost disappeared, replaced by the gray rat. But still, a comprehensive and accurate answer to the question of why the plague epidemics stopped has not yet been found.
Cholera is often compared to the plague because of its transience and lethality. Cholera was brought to Europe only around 1816 from India, where it had been known since ancient times. In Russia, before 1917, more than 5 million people suffered from cholera, and half of them died.
By the end of the 20th century. Thanks to prevention, cholera epidemics have become quite rare. We are currently living in the era of the 7th pandemic. For Russia, the problem remains relevant; the epidemic situation is assessed as unstable.
Preventing cholera
Since cholera is a “disease of dirty hands,” it is necessary to systematically wash your hands before each meal, and in no case touch the mucous membranes of your mouth with unwashed hands. Wash your hands only with hot water. Products should be kept in places protected from flies and insects. Sanitation and hygiene skills are the main weapon in the fight against cholera.
TUBERCULOSIS.
The ominous symptoms of pulmonary tuberculosis (consumption) - weakness, shortness of breath, and in advanced cases, hemoptysis - were familiar to the inhabitants of Ancient Egypt and people who lived hundreds of thousands of years ago. This was shown by studies of their remains.
In ancient times and the Middle Ages, there was a belief that crowned persons could cure tuberculosis with their touch. English King Charles II in the 17th century. touched more than 90 thousand patients. A considerable fee was charged for the “treatment”, which went to the royal treasury.
Only in the 19th century. The first tuberculosis sanatoriums appeared. But the real fight against this disease began after Robert Koch discovered the tuberculosis bacterium in 1882.
Tuberculosis has not been completely defeated today. In the former Soviet Union, prisons and camps became breeding grounds for tuberculosis, where a significant proportion of prisoners became infected with the disease. Tuberculosis is a social infection. “The poorer the population, the more often they suffer from tuberculosis”
Prevention of tuberculosis
For newborns, BCG vaccination is necessary. Next, at the stage of their maturation, a mandatory (every 8-12 months) Mantoux reaction is performed. It is advisable to choose a place of residence in dry, well-lit places. The apartment should be systematically wet cleaned and ventilated.
Paths of transmission of pathogenic bacteria
Airborne;
Handshake;
Houseware;
Contaminated water and food;
Disease carriers are rodents, fleas, ticks, lice, and cattle.
The poet Vladimir Mayakovsky, who took on all kinds of propaganda work, even wrote poetic explanations for a poster dedicated to the fight against cholera : “Citizen!
So as not to die from cholera,
take such measures in advance.
Don't drink raw water.
Drink only boiled water.
Also, do not drink kvass on the street.
Boiling water is a lot of work.
So that you can keep up with your kvass early,
they just cook it from the tap...”
How does a bacterial infection progress?
With the development of a bacterial infectious process One of the first symptoms will be fever. Fever is a protective reaction of the body, since body temperature up to 39 degrees stimulates the immune system. If the body temperature rises above 39 degrees, then it must be brought down with paracetamol or, indirectly, with antibiotics (a decrease in body temperature within 24-48 hours from the start of antibiotic therapy is a sign of a properly selected antibacterial drug).
Another manifestation of a bacterial infectious process is intoxication syndrome. It manifests itself as a deterioration in health, apathy, decreased mood, headaches, pain in muscles and joints, nausea, vomiting, and the like are possible. To relieve these symptoms, you need to drink a lot of warm water (at least 2 liters per day). Excess water will dilute bacterial toxins, reducing their concentration, and also remove some of them in the urine.
These two signs of bacterial inflammation are universal to almost all infections. All other signs are determined by the characteristics of a particular pathogen, their exotoxins and other factors of aggression.
Immunity– the body’s immunity to a foreign agent, in particular to bacteria.
The human immune system protects our body constantly and always.
Task and human immunity find and neutralize bacteria that have entered the body, as well as their toxins.
To prevent illness from some bacterial diseases, vaccinations are carried out. In this case, weakened pathogens or poisons secreted by them are introduced into the body of a healthy person. The body creates special substances that help the subsequently vaccinated person quickly cope with pathogenic bacteria.
Practical part
It must be said that recently there has been a “replacement” of bacterial infections by viral ones, but their significance does not cease to be relevant. For example, in the 90s, having “calmed down” that diphtheria was not being registered, the percentage of people vaccinated against this infection decreased, resulting in an increase in morbidity and outbreaks of this infection with deaths that could have been avoided. Among bacterial infections, intestinal infections occupy a huge place:
- cholera
- typhoid fever
- dysentery
- salmonellosis.
Incidence of bacterial infections by country
| № | Diseases | Cases | Causes | Prevention |
| 1. | Cholera | 1994 – Chechen Republic, 415 cases; 2005 – Rostov region; 2006 – Murmansk region; 2008 – Bashkiria; 2010 – Moscow. |
Changes in socio-economic conditions: refugees, tourism, pilgrims; deterioration of the environmental situation – | poor water quality - Improving water quality Cleaning, sewerage of populated areas; Strict supervision over the work of public catering, the quality of products, removal of sick people from work; Compliance with personal hygiene rules; |
| 2. | Veterinary control of animals | Typhoid fever | Cases of infection are constantly being recorded in Russia | |
| 3. | Migration, unsatisfactory state of cleaning of populated areas; poor quality of water supply, public catering | Dysentery Salmonellosis | ||
| 4. | Failure to comply with personal hygiene rules, consumption of contaminated products | Tuberculosis | The number of new cases has been constantly increasing in recent years | Social – poverty of the population - Early immunization of newborns; Conducting the Mantoux reaction for all children; |
Fluorography (adult population)
What about bacterial infections in our area? What are their causes and prevention? I learned about this from the infectious disease specialist of the territorial department of Rospotrebnadzor in the Valdai region, Natalya Tomovna Guseva.
| Incidence of bacterial infections in the region | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | ||||||||||
| Disease | area | |||||||||||||||||
| region | abs | region | abs | region | abs | region | abs | region | abs | region | abs | region | abs | region | abs | region | ||
| per 100 thousand | 9 | 59,4 | 5 | 33,0 | 5 | 34,0 | - | - | - | - | - | - | - | - | - | - | ||
| Dysentery | - | - | - | - | 2 | 13,7 | - | - | - | - | - | - | 3 | 23,7 | 1 | 8,0 | ||
| Salmonellosis | 1 | 6,6 | - | - | 15 | 103,2 | 3 | 20,6 | 7 | 49,2 | 4 | 28,7 | - | - | 1 | 8,0 | ||
| Scarlet fever | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | 7 | |
| Diphtheria | - | - | - | - | - | - | - | - | - | - | 3 | 21,5 | - | - | - | - | 7221 | |
| Whooping cough | 1 | 6,6 | - | - | - | - | - | - | - | - | 1 | 7,2 | - | - | 1 | 8,0 | ||
| Meningococcal infection | 9 | 59,4 | 3 | 19,8 | 7 | 48,1 | 9 | 61,9 | 10 | 70,3 | 11 | 79,0 | 4 | 31,6 | 3 | 24 | ||
Tuberculosis
Recently, there have been many parents who refuse to vaccinate their children, thereby exposing their children to mortal danger, as well as endangering other children. It is reliably known that a reduction in morbidity is possible only with a high level of immunization of the population - 99%; in 2012, this figure for all infections in our area decreased to 94%.
The implementation of this research allowed me to develop skills in working with additional literature, the ability to conduct research, and substantiate the results of research.
During my research, I came to the following conclusion:
1) bacterial diseases are still one of the most common diseases;
2) to protect yourself from bacteria, you need to follow the rules of personal hygiene, do not eat unwashed fruits and vegetables, do not drink unboiled water, eat only fresh foods, and, of course, do not forget to wash your hands often.
3) an effective measure to prevent bacterial infections is immunization of children and adults.
Practical value The work is that the materials obtained can be used in biology lessons when studying the topic “Bacteria” or during extracurricular activities.
LITERATURE
1. Borisov L.B. and others. Medical microbiology, virology, immunology. M.: Medicine, 1994.
2. Vasiliev K.G. Segal A.E. History of epidemics in Russia. M.: Medgiz, 1960.
3. Likum A. Children's encyclopedia “Everything about everything.” M.: AST, 2008.
4. Galpershtein L.Ya. My first encyclopedia. ROSMEN, 2007.
5. Children's encyclopedia “I explore the world.” Medicine. M.: Astrel, 2006.
6. Internet resources (illustrated materials for the presentation)
Slide 2
OBJECTIVES OF THE LESSON:
1. Study the pathogens that are currently the most dangerous for modern humans, domestic animals and crops; conditions and routes of infection; basic methods of prevention and protection. 2. Prove that basic rules of personal hygiene are an integral part of protecting a person from infection 3. Make sure of the need to use anti-infective measures. 2
Slide 3
INTRODUCTION Infectious morbidity of the population during emergencies
Slide 4
1. CLASSIFICATION OF PATHENIC MICROORGANISMS AND DISEASES CAUSED BY THEM1.1 PATHENIC MICROORGANISMS
Slide 5
1.2 BENEFICIAL BACTERIA
Products rich in bacteria: fermented milk: yogurt, kefir, fermented baked milk, yogurt, ayran, tan, kumiss; everything sauerkraut: cabbage, kvass, pickled apples, etc. Destroy beneficial bacteria: preservatives, dyes, flavors, antibiotics 5
Slide 6
2 ESPECIALLY DANGEROUS INFECTIOUS DISEASES OF HUMAN 2.1 ROUTES OF TRANSMISSION OF THE PAGUENT
1) intestinal (cholera, typhoid fever, botulism); 2) respiratory (flu, plague); 3) blood (transmission) (AIDS); 4) external integument (contact) (natural smallpox). 6
Slide 7
2.2 BASIC DEFINITIONS
An epidemic focus is the place of origin and residence of the diseased person, the people and animals around him, as well as the territory within which people can be infected by infectious disease agents. Epidemic is a widespread spread of an infectious disease, significantly exceeding the incidence rate usually recorded in a given territory. A pandemic implies an unusual increase in morbidity, both in level and in scope, covering a number of countries, entire continents and even the globe. 7
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2.3 CONDITIONS FOR THE EPIDEMIC
The emergence and maintenance of an epidemic process is possible in the presence of components: a source of infection; mechanism of infection transmission; transmission routes; receptive person. 8
Slide 9
2.4 ESPECIALLY DANGEROUS INFECTIOUS DISEASES CH U M A
Plague is an acute infectious disease that is caused by plague bacilli - special pathogens that can spread throughout the body.
Forms: pulmonary; cutaneous bubonic; bubonic. 9
Slide 10
H O L E R A
2) Cholera is an acute infectious disease of the human gastrointestinal tract, caused by Vibrio cholerae, with a fecal-oral transmission mechanism. 10
Slide 11
YELLOW FEVER
3) Yellow fever is an acute infectious disease caused by a specific virus and transmitted by mosquitoes of strictly defined species. eleven
Slide 12
TRANSMITTED IMMUNE DEFICIENCY SYNDROME (AIDS)
4) AIDS - acquired immune deficiency syndrome. Caused by the human immunodeficiency virus (HIV). 12
Slide 13
TYPHOID FEVER
5) Typhoid fever and paratyphoid fevers A and B - a group of acute infectious diseases with a fecal-oral transmission mechanism, caused by Salmonella and similar in clinical manifestations. 13
Slide 15
D I F T E R I A
7) Diphtheria is an acute infectious disease with airborne transmission, characterized by toxic damage to the cardiovascular and nervous systems, a local inflammatory process with the formation of fibrous plaque. 15
VIRAL HEPATITIS
8) Viral hepatitis A, B and C is an infectious disease of a viral nature, manifested by intoxication, liver damage and, in some cases, jaundice. Hepatitis C is equivalent to AIDS. 16
Slide 17
FLU
9) Influenza is an acute viral infectious disease; transmitted by airborne droplets. It is characterized by an acute onset, intoxication, fever and damage to the respiratory tract. 17
Slide 18
ANTHRAX
10) Anthrax is an acute infectious disease from the group of zoonoses, which in humans occurs in the form of cutaneous, pulmonary, and intestinal forms. 18
Slide 19
B O T U L I Z M
11) Botulism is a potent toxin. 19
Slide 20
3 ESPECIALLY DANGEROUS ANIMAL DISEASES3.1 BASIC DEFINITIONS
Epizootic is the widespread spread of infectious diseases in a household, district, region, or republic. Epizootics are characterized by mass distribution, a common source of the infectious agent, simultaneity of damage, and periodicity and seasonality. Infectious diseases that manifest themselves as epizootics include foot and mouth disease, swine fever, Newcastle disease, etc. Panzootic is an unusually wide spread of an infectious disease that covers the entire country, several countries, and a continent. Infectious animal diseases that tend to panzootics include foot-and-mouth disease, plague of cattle, pigs, and birds. 20
Slide 21
3.2 ESPECIALLY DANGEROUS DISEASES
1) Foot and mouth disease is a highly contagious, acute viral disease of domestic and wild animals, characterized by fever and damage to the mucous membrane of the oral cavity, skin, udder and limbs. 21
Slide 22
BIRD FLU
2) Bird flu H5N1 is dangerous for humans because the virus can mutate in the human body and then be transmitted from person to person. 22
Slide 23
4 ESPECIALLY DANGEROUS DISEASES AND PLANT PESTS4.1 BASIC DEFINITIONS
Epiphytoty is the spread of infectious diseases over large areas over a certain period of time. Panphytotia is a mass disease covering several countries and continents. 23
Slide 24
4.2 ESPECIALLY DANGEROUS LESIONS STEM RUST OF WHEAT AND RYE
1) Stem rust of wheat and rye - mainly affects the stems and leaf sheaths of cereals. The ability of rust diseases to spread rapidly is due to the high fertility of the pathogens. The complete development cycle of the pathogen consists of a sequential series of sporulations. Fungus (causative agent). 24
5 PRECAUTIONS
Early identification of patients. Sanitizing people. Disinfection of the territory. Disinfection of food waste. Using the media to alert and inform the population. 27
Slide 28
5.1 ACTIONS FOR INFECTIOUS DISEASES
Observation is the implementation of enhanced medical observation, partial and anti-epidemic measures aimed at eliminating the source of infection. Quarantine is the isolation in a specially adapted room of healthy persons who may have had contact with carriers of infectious diseases. 28
Slide 29
LITERATURE
1) Kruglov V.A. Protection of the population and economic facilities in emergencies. Radiation safety. Mn., “Amalthea” - 2003, - 367 p. (Chapter 3) 2) Mikhnyuk T.F. Life safety - Mn.: “Design PRO”, 1998, 239 p. (Chapter 5) 3) Babovoz S.P. , Kruglov V.A. Generalov V.A. Civil defense in the Republic of Belarus. Mn., “Amalthea” - 2000, - 366 p. 29
Bacteria
Discovery of bacteria Diversity and living environments Sizes and shapes of bacteria Structure of bacteria Nutrition and respiration of bacteria Reproduction of bacteria Unique adaptation to survival The importance of bacteria Sensory functions and behavior Plan:
Bacteria were first discovered and described in 1683 by Anthony van Leeuwenhoek. The first discoveries of Leeuwenhoek's microscope What Leeuwenhoek saw.
Bacteria are allocated to the independent kingdom Monera. Currently, about 3,000 species of bacteria are known.
There are no places on the globe where they do not live.
The most bacteria-rich habitat is soil. 1 g of arable land contains from 1 to 20 billion bacteria.
Even in 1 g of ice in Antarctica you can find up to 100 bacteria.
By the end of the first day, 12 types of bacteria live in the body of a newborn baby.
Bacteria are the smallest prokaryotic organisms with a cellular structure. The size of most bacteria ranges from 0.2 to 1.3 microns. The shape of bacteria is quite diverse.
The following groups of bacteria are distinguished: A - cocci (more or less spherical), B, C, D, E - bacilli (rods or cylinders with rounded ends), G - spirilla (rigid spirals) E - spirochetes (thin and flexible hair-like forms) . Shapes of bacteria
Organisms with such a cell structure are called prokaryotes (“pre-nuclear”). Structure of bacteria
Bacteria that require free oxygen are called aerobic, and those that can do without it are called anaerobic. Facultative anaerobic bacteria can live both in an oxygen-containing environment and in an oxygen-free environment (for example, lactic acid bacteria). And for obligate anaerobic bacteria (butyric acid bacteria, tetanus bacteria), free oxygen is toxic. Respiration of bacteria
Under favorable conditions, bacteria multiply very quickly - by direct division (amitosis) into two cells approximately every 40-60 minutes. If nothing interfered with such division, then one bacterium would multiply in 5 days so that its offspring would occupy all the seas and oceans of our planet. This does not happen: due to lack of food, accumulation of metabolic products, death from unfavorable conditions, and bacteria being eaten by other organisms. Recently, substances have been discovered in bacteria that regulate their numbers and “do not allow” them to multiply beyond a certain limit. Bacteria reproduction
A small group of bacteria - bacilli - are capable of forming spores. In this case, the bacterial cell undergoes a number of significant biochemical and morphological changes: the amount of free water in it decreases, enzymatic activity decreases, the cell shrinks and becomes covered with a very dense membrane. Spores provide bacteria with the ability to tolerate unfavorable conditions. They can withstand prolonged drying, heating above 100 °C and cooling to almost absolute zero. Adaptations to adverse conditions
Thanks to their vital activity, the decomposition and mineralization of organic substances of dead plants and animals occurs. The resulting simple inorganic compounds (ammonia, hydrogen sulfide, carbon dioxide) are involved in the general cycle of substances, without which life on Earth is impossible. Bacteria take part in soil-forming processes. The importance of bacteria
A special role in nature is played by bacteria that are capable of binding free molecular nitrogen, which is completely inaccessible to higher plants. Inhabiting the soil, such free-living bacteria enrich it with nitrogen. The importance of bacteria
Another group of nitrogen fixers, nodule bacteria, settle in the roots of leguminous plants. Penetrating through their root hairs into the root, nodule bacteria cause strong growth of root tissue in the form of nodules. Receiving carbohydrate nutrition from the plant, bacteria begin to fix nitrogen with the formation of ammonia, and from it nitrites and nitrates. The resulting nitrogenous substances are sufficient for both bacteria and plants. In addition, some nitrogenous compounds are released into the soil, increasing its fertility. Here we encounter the phenomenon of symbiosis - the mutually beneficial cohabitation of two organisms: bacteria receive from their host the carbohydrates necessary for nutrition, formed during photosynthesis, and they themselves supply the plant with amino acids and other products of molecular nitrogen fixation.
Bacteria play a positive role in human economic activity. Lactic acid bacteria, feeding on milk sugar (lactose), secrete lactic acid, which causes ripening. This feature is used for the production and preparation of various food products from milk (sour cream, curdled milk, kefir, butter, yogurt, cheese), as well as for pickling and soaking vegetables, and for ensiling feed.
Bacteria play a positive role in human economic activity. Many industries cannot do without bacterial waste products such as ethyl alcohol, acetic acid, butyl alcohol, and acetone.
Bacteria play a positive role in human economic activity. Drying tobacco leaves, tanning leather, producing cocoa and coffee cannot be done without bacteria. During the life of bacteria, biologically active substances are formed - antibiotics, vitamins, amino acids. Spore-bearing anaerobic bacteria, which cause the destruction of pectin substances during the fermentation process of flax and hemp, destroy the intercellular substance and contribute to the release of spinning fibers. Humans also use bacteria to treat wastewater: a community of a wide variety of bacteria destroys and oxidizes all substances coming with waste, and the resulting mass after drying is used as fertilizer. Using genetic engineering, genes encoding substances needed by humans, such as insulin or growth hormone, are introduced into the bacterial genome.
Many bacteria cause spoilage of a wide variety of materials and foods. Along with the release of carbon dioxide, ammonia and energy, the excess of which causes the substrate (for example, manure, wet hay, grain) to heat up until it ignites spontaneously, bacteria form a number of toxic substances. Negative role of bacteria
The causative agents of these diseases have claimed many times more human lives than all wars combined. Russian chronicles brought to us human pain and bitterness. “As soon as five people left the city, the city shuttered” - this is how the chronicle tells about the plague epidemic in Smolensk in 1387. The negative role of bacteria
By infecting plants, bacteria cause so-called bacterioses: spotting, wilting, burns, wet rot, tumors. Negative role of bacteria
Conditioned reflexes in bacteria are unknown, but they do have a certain kind of primitive memory. Sensory functions and behavior.
Many bacteria have chemical receptors that register: - changes in the acidity of the environment; - the concentration of various substances, such as sugars, amino acids, oxygen and carbon dioxide. Each substance has its own type of such “taste” receptors, and the loss of one of them as a result of mutation leads to partial “taste blindness”. - many mobile bacteria also respond to temperature fluctuations, and photosynthetic species respond to changes in light. Some bacteria perceive the direction of magnetic field lines, including the Earth's magnetic field, with the help of particles of magnetite (magnetic iron ore - Fe3O4) present in their cells. In water, bacteria use this ability to swim along lines of force in search of a favorable environment. Sensory functions and behavior.
