History of the Development of Microorganisms

The history of the unfolding of the world of microorganisms began with the discovery of a microscope by Anthony van Leeuwenhoek (1633-1723). At first, the microscope was very simple finding, only equipped with one lens with a very short focus distance, but can produce clear shadows that are equivalent to magnification 50-300 times. Observations made by Leeuwenhoek include observations on the microscopic structure of seeds, plant tissue, and small invertebrates. The biggest discovery of his day and is known as the world of microorganisms, which is called animalculus or small animals. Animalculus are various types of microorganisms that are now known as protozoa, algae, yeast, and bacteria.

Spontanea Generatio Conflict

Leewenhoek's discovery of these small animals is a very serious debate among microbiologists. In connection with Leewenhoek's findings, two opinions emerged, one said that the appearance of small animals due to the process of decomposition of plants or animals, or through the fermentation process. This opinion supports the theory that living things come from inanimate objects or abiogenesis, and the concept is known as spotanea genaratio. Another opinion says that these small animals come from small animals before as well as higher organisms. Opinions or theories that say this is known as biogenesis. The existence of differences of opinion caused microbiology to not develop and this continued until the debate was resolved by the proof of the truth of the biogenesis theory. This verification requires a variety of experiments that seem simple but require more than 100 years.

Proof of Abiogenesis Unrighteousness

Franscesco Redi (1626-1697) with his experimental results proved that the caterpillars found in rotten meat are larvae derived from fly eggs, not from inanimate objects (Generatio Spontanea theory). What about the origin of microorganisms that can only be seen with a microscope? John Needham (1713-1781) conducted an experiment by cooking a piece of meat to remove existing organisms, then placing them in an open jar. Based on his observations found a colony on the surface of the meat, so it was concluded that microorganisms occur spontaneously from meat.

In 1769, Lazarro Spalanzani (1729-1799) conducted an experiment by boiling meat broth for 1 hour and placing it in a jar which was tightly closed, the experimental results showed no microorganisms were found in the broth. So Lazarro Spalanzani's experiment challenges the Abiogenesis theory. On the contrary, Needham said that based on his experiments the source of living things came from the air while the Spalanzani experiment did not interact directly with the air. After nearly 100 years of Needham's experiment, and there is no certainty of truth between the two experiments, there are two researchers who try to solve the controversy about the role of the air. In 1836, Franz Schulze conducted an experiment by passing a strong acid solution into a closed tube containing cooked meat. In 1837, Theodore Schwann conducted an experiment by flowing air through a heat pipe into a closed tube filled with broth. Both did not find the presence of microorganisms because microorganisms have died by the presence of strong acids and heat, but supporters of the Generatio Spontanea theory argue that the presence of strong acids and heat will change the air so that it does not support the growth of microorganisms. Finally, in 1954 researchers emerged to resolve the debate, by conducting an experiment using a closed tube containing a heated broth. Then the tube is inserted into the tube which is partly filled with cotton and the ends are left open, so that microorganisms will be filtered and air can still enter. As a result, no microorganisms were found in the meat broth, this proves that the Generatio Spontanea theory is wrong.

Proof of Biogenesis Theory

In the same period a new scientist from France, Louis Pasteur (1822-1895), a chemist, paid attention to microorganisms. Pasteur was interested in examining the role of microorganisms in the wine industry, especially in making alcohol. One of the supporters of the theory of Generatio Spontanea who lived during Louis Pasteur was Felix Archimede Pouchet (1800-1872). In 1859 Pouchet published many papers supporting the theory of Abiogenesis, but he could not refute Pasteur's discoveries. Pasteur as a scientist, to confirm his opinion, conducted a series of experiments. One of Pasteur's experiments was using a long neck which was bent and known as a swan neck (Figure). This vessel is filled with broth and then heated. In these conditions the air can freely pass through a swan neck tube or pipe but in the broth area no microorganisms are found. The analysis shows that microorganisms along with dust will settle to the U-shaped tube so that it cannot reach the broth. Pasteur went through the same experiment, taking the tube to the Pyrenes and the Alps. The observations found that microorganisms were carried by dust by the air, so Pasteur concluded that the cleaner / purer the air entering the vessel, the less contamination that occurs.

Picture: Goose-Necked Pasteur Bottle Remains Sterile Because The Neck Curve Holds Dust Particles
Picture: Goose-Necked Pasteur Bottle Remains Sterile Because The Neck Curve Holds Dust Particles

One of the classic arguments against the Biogenesis theory is that heat used to sterilize air or materials is considered to damage vital energy, because without the vital force microorganisms cannot arise and be spontaneous. John Tyndall responded to this argument by saying that air can be easily released from microorganisms through a series of experiments namely putting a test tube containing sterile broth into a closed box. Air from outside enters the box through a pipe that has been bent to form a U-shaped base like a spiral (Figure). It is proven that although outside air can enter the box containing the tube with the broth inside, no microorganisms are found. Pasteur and Tyndall's experiment results spurred the acceptance of the concept of biogenesis. Next Pasteur focused his research more on the role of microorganisms in wine making and microorganisms that cause disease.
Image: Broth Water remains Sterile in a Dust-Free Tyndall Incubation Room. In both cases the broth was exposed to the air, but it was dust free
Image: Broth Water remains Sterile in a Dust-Free Tyndall Incubation Room. In both cases the broth was exposed to the air, but it was dust free

Theory About Fermentation

One example of the fermentation process can occur if the grape juice is left, in the process a series of changes in biochemical, alcohol, and other compounds that ultimately produce wine (wine). Pasteur's reason was against the opinion of Generatio Spontanea because of his belief that wine fermentation products were the result of existing microorganisms, not fermentation to produce microorganisms as was believed at that time. In the 1850s Pasteur solved a problem that emerged in the wine industry, namely by conducting research on good grapes and less good grapes, then found different microorganisms. Certain microorganisms dominate good wine, while other types of microorganisms dominate poor wine. Pasteur concluded that the selection of suitable microorganisms would produce good wine products. Based on this analysis Pasteur destroy microorganisms contained in grape juice by heating it. After chilling into the juice the inoculated grapes of good quality with the desired microorganism content. The results showed that the wine obtained was of good quality and did not change the aroma during storage because it had been heated for several minutes at 50-60ºC. This process is known as pasteurization which is now widely used in the food industry. Whereas, previously people increased fermentation products through trial and error, because of their ignorance that the quality of the product depends on certain microorganisms.

Discovery of Bacteria with spores

John Tyndall (1820-1893), also supported Pasteur's opinion, through his experiments using liquid organic material that had been heated in boiling salt water for 5 minutes and placed in a dust-free room, apparently the liquid organic material did not rot even if stored for months. If without heating, there will be decay. Tyndall in his experiment found that there was a thermolable phase (the bacterium during growth did not resist heating) and thermoresistant to the bacteria (resistant to heat). The results of the investigation of a German botanist named Ferdinand Cohn, can be seen microscopically that in phasetermoresisten, bacteria can form endospores. Based on the finding, a way to sterilize materials containing spore-forming bacteria is sought. The intended method is by heating which is interrupted and repeated several times, the process is known as Syndallization. The heating process is as follows, initially heating is carried out at 100 ° C for 30 minutes, then left at room temperature for 24 hours, this method is repeated 3 times. When left at room temperature, the surviving Syspora bacteria will germinate to form a growth / thermolable phase, so that it can be turned off at the next warm-up.

The Role of Microorganisms in the Transformation of Organic Materials

Various materials overgrown by microorganisms will undergo changes in chemical composition. Chemical composition changes that occur are known as fermentation (yeast) and putrefaction. Fermentation is the process of breaking down organic compounds into simple compounds that the end result of alcohol or organic acids, for example, occurs in materials that contain carbohydrates. Decay is a decomposition process that produces a foul odor, as in decomposition of material containing protein. In 1837, C. Latour, Th. Schwanndon, and F. Kutzing separately found that in sugar fermented alcohol always found yeast, so it can be concluded that the change of sugar into alcohol and CO2 are physiological functions of these yeast cells. This biological theory was opposed by J. Berzelius, J. Liebig, and F. Wahler. They argue that fermentation and decay are ordinary chemical reactions. This can be proven in 1812 the successful synthesis of urea organic compounds from inorganic compounds. Pasteur researched a lot about the fermentation process (1875-1876). One time a company making wine from sugar beet, produced sour wine. Based on his microscopic observations, some of the yeast cells are replaced by other cells that are round and stem with smaller cell sizes. The existence of these smaller cells turns out to result in most of the alcohol fermentation process being pushed by another fermentation process, namely lactic acid fermentation. Based on this fact, it is further proved that each particular fermentation process is caused by the activity of certain microorganisms, which are specific to the fermentation process. For example alcohol fermentation by yeast, lactic acid fermentation by Lactobacillus bacteria, and citric acid fermentation by Aspergillus mushrooms.

Discovery of Anaerobic Life

During his research on butyric acid fermentation, Pasteur discovered a life process that did not need air. Pasteur showed that if the air was blown into the butyrate fermentation vessel, the fermentation process was hampered, and could even be stopped altogether. Based on these observations, two terms of life of microorganisms emerged, namely (1) anaerobic life, for microorganisms that do not require oxygen, and (2) aerobic life, for microorganisms that require oxygen.

Physiologically the existence of fermentation can be used to find out several things. Oxygen is generally needed by microorganisms as agents to oxidize organic compounds to CO2. The oxidation reaction is known as "aerobic respiration", which produces energy for the life of the body and its growth. Other microorganisms can get power by breaking down organic compounds by anaerobic fermentation, without the need for oxygen. Some types of microorganisms are obligatory anaerobic or perfect anaerobic. Another type is facultative anaerobic, which has two mechanisms for getting energy. If there is oxygen, energy is obtained by aerobic respiration, when there is no oxygen energy is obtained by anaerobic fermentation. Pasteur found that aerobic respiration is an efficient process for producing energy.

Enzyme Discovery

According to Pasteur, the fermentation process is a vital process for the life of microorganisms. This opinion was opposed by Bernard (1875), that yeast can break down sugar into alcohol and CO2 because it contains biological catalysts in its cells. Biological catalyst can be extracted as a permanent solution that can show the ability of fermentation, so that fermentation can be made as a process that is no longer vital (without cells).

In 1897, Buchner was able to prove Bernard's idea, that when grinding yeast cells with sand and adding large amounts of sugar, it was seen that the mixture was freed of CO2 and a little alcohol. These discoveries paved the way for the development of modern biochemistry. In the end it can be seen that the formation of alcohol from sugar by yeast, is the result of a sequence of several chemical reactions, each of which is catalyzed by a specific biocatalyst or known as an enzyme.

Causes of Disease Microorganisms

Pasteur used a special term to describe the damage to wine by microorganisms, which he referred to as Beer disease. Pasteur also strongly suspected the role of microorganisms in causing disease in high-level bodies. This is proven by the discovery of fungi that cause disease in wheat plants (1813), potato plants (1845), diseases of silkworms, and on human skin. In 1850 it was discovered that in the blood of animals affected by anthrax there were rod-shaped bacteria. Davaine (1863-1868) proved that the bacteria is only found in sick animals, through artificial transmission using the blood of sick animals that are infected in healthy animals so that healthy animals are then infected with the same disease. Proof that anthrax is caused by bacteria was also carried out by Robert Koch (1876), until the discovery of Koch's postulate which was steps for proving that a microorganism is the cause of disease (Figure mouse).

Koch's postulates in general are as follows.

  1. A microorganism that is suspected to be the cause of a disease must exist at every level of the disease.
  2. These microorganisms can be isolated from diseased bodies and grown in the form of pure cultures.
  3. If the pure culture is injected into healthy and sensitive animals, it can cause the same disease.
  4. Microorganisms can be isolated again from the body that has been made sick.
Image: Illustration of Koch's Postulate Steps
Image: Illustration of Koch's Postulate Steps

Virus discovery

Iwanowsky through his experiments found the ability of bacteria-free filtrate (a liquid that has been filtered with a bacterial filter) derived from tobacco plant extracts affected by mosaic, it still can still cause infections in healthy tobacco plants. Based on this fact, it can be seen the existence of a living body that has a size smaller than bacteria (submicroscopic) because it is able to escape from the bacterial filter, and the body is known as a virus. Proof of diseases caused by viruses, can be used postulate River (1937), as follows.
  • The virus must be inside the host cell.
  • Filtrate of infected material does not contain bacteria or other microorganisms that can be grown in artificial media.
  • Filtrate can cause disease in sensitive bodies.
  • The same filtrate and derived from the sensitive host must be able to cause the same disease again.

Summary

Microbiology is a branch of biology that studies microorganisms and to understand it needs to be supported by some basic sciences such as physics, chemistry, and biochemistry. Microbiology has experienced rapid development into a variety of sciences, including virology, bacteriology, mycology, food microbiology, soil microbiology, and industrial microbiology.

Microbiological developments include: The first period, around 1675, began with the opening of the secret of a world of microorganisms through the observation of Leeuwenhoek. The second period, spontaneous generation conflict or conflict until the concept of abiogenesis is broken. In the third period, the discovery of disease and fermentation resulted in Koch's and the River's postulates, which are used today. Important concept: Microbiology learns about small microorganisms that cannot be seen with the naked eye.

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