Good and harmful MICROORGANISMS
Our project English and science will be concerned with the study of microorganisms, which, as the word itself says, are
including:
The science that studies these microscopic organisms, sometimes called microbes, is microbiology. Most of the microbes cannot be seen without a microscope that magnifies objects at least 1,000 times and most viruses are so tiny that they can be examined only with electron microscopes that magnify many thousands of times.
The scientists that work in the field of microbiology are called microbiologists. Many of them study the relationships between microbes and man, animals and plants.
Medical microbiologists investigate the role of microorganisms in human and animal diseases and seek ways to prevent and cure these diseases.
Agricultural microbiologists study plant diseases, the role of microorganisms in soil fertility, and spoilage of farm products by microorganisms.
Industrial microbiologists use microorganisms to produce such products as alcoholic beverages, aminoacids, antibiotics, citric acid and vitamin B.
General microbiologists study the basic features of microorganisms, including ecology, genetics, metabolism, physiology, and structure.
Microorganisms also play an important part in sewage treatment and pollution control.
A rapidly growing new branch of microbiology is marine microbiology, which focuses on the vast number of microorganisms in the oceans. Some microorganisms are being grown and harvested experimentally for use as food.
Scientific classification is a method scientists have developed to arrange all animals and plants in related groups. It indicates certain relationships among animal groups and among plant groups..
In scientific classification the kingdom is the largest group, and the species is the smallest.
Kingdom contains most kinds of animals and plants. All animals belong to the animal kingdom
and all plants are members of the plant kingdom.
However, some living things so small that they can be seen only under a microscope seem to have some of the characteristics of animals and some of plants. So some scientists classify them in a special kingdom called Protista
Other scientists separate them into two kingdoms: the Protista or protists, and the Monera or monerans.
In this classification, the Monerans include bacteria and blue-green algae, which are sometimes considered plants.
Protista is a group of one-celled organisms. Protists may have the characteristics of both animals and plants.
Protista includes organisms called Protozoans.
The word Protozoan comes from Greek and means first animal.
There are about 20,000 kinds of Protozoa; nearly all of them live in water.
The ameba is one of the simplest protozoans. The single cell that makes up its body carries on all the necessary life processes by itself. The bodies of some protozoans contain chlorophyll, the green substance also found in plants. This enables them to make their own food.
In spite of their small size, protozoans are very important for both human beings and other animals.
Some protozoans, such as the foraminifers are, are covered with stony shells. When the animals die, they settle to the bottom of the sea and contribute to the formation of limestone (see, for example the chalk cliffs in southern England).
Many one-celled animals are serious enemies of human beings and other animals. Malaria and African sleeping sickness are among the diseases that they cause.
Fungi is the name of a group of simple organisms that have no green colouring matter; because of this fact, they cannot manufacture their own food. They must live on dead or living plants or animals.
Sometimes fungi get their food by simply absorbing the minerals, sugars and water from the material they live on.
Parasitic fungi, which feed and on living plants and animals, are usually harmful and destroy many useful plants but many fungi, including yeasts, several mushrooms and truffles, are useful and can be eaten as food. Still other fungi are used in medicine.
Following this basic classification of microorganisms, we will next concentrate our attention on bacteria that, together with blue-green algae make up the monera kingdom.
However, let us first draw a short outline of what bacteriology is, when it was born and the great contribution to its development of a scientist who is considered the father of modern bacteriology,
Louis Pasteur.
BACTERIA are tiny one-celled organisms with a simple cell structure. They are among the
smallest of all cells. Most bacteria measure from about 0.4 to 10 microns across. Scientists have classified them in different ways. In our classification table they are placed in the Monera group, whose members have some characteristics of both plants and animals. According to another classification they belong to the Protista kingdom.
Bacteria are probably the most numerous of all organisms. They can be found almost everywhere: Many bacteria live in the soil, especially in the upper layers. . The air may have more than 3,500 per cubic metre. Air currents carry them 27,000 metres high. Bacteria have been found in the ocean at a depth of 10,000 metres and they were on the Earth when life began.
Bacteria were first seen in 1676 by Anton van Leeuwenhoek, a Dutch merchant who, though he used very crude microscopes, described various bacteria accurately.
Bacteriology developed as a science during the late 1800's. The most famous baceriologists of that time were Louis Pasteur and Robert Koch.
Pasteur, a French chemist, showed that bacteria cause fermentations ( chemical changes), such as the souring of milk or the changing of wine into vinegar. He also identified the specific bacteria that cause certain kinds of fermentations. Koch became the first scientist to show that specific bacteria cause certain diseases. He discovered that a rod-shaped bacterium, Bacillus anthracis, causes anthrax in cattle and man. He also found that another rod-shaped bacterium, Mycobacterium tuberculosis, causes tuberculosis.
The development of the electron microscope in the 1930's allowed bacteriologists to study the interior of bacterial cells. Today scientists are still trying to learn more about how bacteria cause diseases. They are also studying ways of using bacteria to help control water pollution and to treat sewage and industrial waste.
Many bacterial diseases may be controlled through vaccines that can be made in different ways. For example these last few days research is going on in several laboratories, first of all in the Pasteur Institute in Paris in the attempt to make a vaccine to cure anthrax, which has come into the headlines over the recent political events in the Usa.
L.PASTEUR (1822.1895), French born, was one of the world's greatest scientists.
His contributions to chemistry, medicine and industry, have greatly benefited mankind. His discovery that bacteria spread diseases saved countless lives. He was a theoretical scientist who applied his discoveries to important practical problems in industry and medicine.
The son of a tanner, he was a slow but careful pupil, who completed his education in chemistry at the Ecole Normale and at the Sorbonne in Paris.
In 1849 he became a science professor in Strasbourg where he began studying fermentation, a sort of chemical breakdown of substances by microbes. His work brought such improvements to brewing and winemaking that some say France was able to save enough money to pay its Franco-Prussian war debt. In 1868, a brain stroke paralyzed him. Despite his poor health, he continued his work. Pasteur was one of the few scientists to achieve fame while still alive.
The Pasteur Institute in Paris, a world centre for the study, prevention and treatment if disease, was founded in 1888 in gratitude to him. Pasteur is buried in a magnificent tomb in the building.
His work in chemistry with the structure of crystals brought him his first recognition. And made him famous by the time he was 26.
He soon started probing the mysteries of bacteriology, showing that living things can come only from living things. Before that, many scientists believed in spontaneous generation, a theory that life can come from things that are not alive, such as dirt. Pasteur also showed that although bacteria live almost everywhere , their spread can be controlled.
His work in industry
Pasteur is credited with saving the silk industry and wine industry in France.. In 1864, he noted that wine turns bitter because of the microbes that enter wine while it is being made.
He suggested that microbes can be killed by applying controlled heat. This use of heat as a means to kill germs became known as pasteurization. . He also used this method to preserve milk and beer and to preserve food.
In 1865, Pasteur set out to help the silk industry. A disease called pébrine was killing a great number of silkworms and eventually he demonstrated that the disease was caused by a microbe that attacked silkworms eggs. He showed that the disease would be wiped out by eliminating this germ in silkworm nurseries.
His work in medicine
Pasteur proved that many diseases are caused by specific kinds of germs that multiply in the body.
He also proved that if microbes are weakened in a laboratory and then placed in an animal's body, the animal develops an immunity (resistance) to the microbe. He called this method vaccination.
He proved its value by vaccinating sheep against a disease called anthrax.
P. began in 1882 to study rabies, a deadly disease spread by the bite of rabies infected animals. He spent endless hours in a laboratory seeking a vaccine to prevent the disease. One day in 1885, a small boy was bitten by a rabid dog. The boy's parents begged Pasteur to save their son. Pasteur hesitated to use his new vaccine on a human, but he finally agreed. After several anxious weeks of treatment, the vaccine proved successful.
Pasteurization is a method of preserving food by heat and cold. It is commonly used for milk, but may also be used for cheese, beer and other foods. It consists in heating milk to at least 63° C for not less than 30 minutes, then chilling it quickly to 10° C or less. Modern dairies use a faster, high temperature method in which the milk is heated to at least 72°C for at least 15 seconds, then cooled. In either method the milk has to be kept cold until used.