The Role of Bacteria For Human

The Role of Bacteria For Human

When we were in our mothers uterus, our body was free from bacteria. But when we were born our body began to make contact with outside world and since that time bacteria entered and became occupants inside our body. Bacteria which enter our body are either beneficial or harmful.

1. Bacteria That are Beneficial for Humans

Several kinds of bacteria can benefit human. For example, there is a bacterium that can fertilize soil by bonding free nitrogen on air and form it into nitrate that is required by plants. There is also bacterium that can decompose dead organisms. Even we also often eat food processed or made by using the help of bacteria. Can you mention the examples?

The example of beneficial bacteria and substance they produce or their use are as follows.

a. Streptomyces aureofaciens, produce aureomycin (substance that can destroy bacteria or virus).

b. Streptomyces venezuellae, produce chloromystin and chloramphenicol.

c. Rhizobium leguminosorum; found in nodules of beans root, can bond free nitrogen on air so it can fertilize soil.

d. Azotobacter chroococcum bacteria that can bond nitrogen.

e. Escherichia coli; live in colon, help in making vitamin K in the body.

f. Lactobacillus casei; can be used in cheese making.

g. Lactobacillus bulgaricus; used in yogurt making.

h. Nitrobacter sp.; can change nitrite that is poisonous in plant into nitrate that is required by the root of the plant.

2. Bacteria That are Harmful for Humans

Bacteria that are harmful for humans are in general parasitic and cause disease. Several examples of bacteria that cause disease are as follows.

a. Neisseria gonorrhoeae; the cause of gonorhea disease (pusurination).

b. Neisseria gonorrhoeae; the case of brain membrane inflamation.

c. Clostridium tetan; the cause of tetanus disease.

d. Bacillus antraxis; the cause of anthrax disease.

e. Vibrio cholerae; the cause of cholera disease.

f. Salmonella typhosa; the cause of typhoid disease.

g. Pasteurella pestis; the cause of pes disease

h. Treponema pallidum; the cause of syphilis disease.

Virus Reproduction

Virus Reproduction

Viruses can proliferate in bacteria cells, animal cells, and plant cells. To explain the virus proliferation, a sample virus attacking bacteria viruses (bacteriophage) is usually used. For example the virus which attacks the bacteria of Escherichia coli.

The proliferation of bacteriophage forms cycles. The cycles of bacteriophage are divided into two, those are lytic and lysogenic cycles.

1. Lytic Cycle of Bacteriophage

In this cycle, the bacteria cells fall to pieces (lysis) so it is called lytic cycle. Their reproduction startes by attacchment of viruses on the bacteria. Virus enzyme dissolves the wall of bacteria cells, so it formes a hole and through the hole, viruses anter their DNA into the bacteria. Later the DNA of virus takes over the duty of bacteria DNA by destroying the DNA of bacteria. Afterwards in the  body of bacteria, DNA, shield protein, and other parts of virus body are synthesized (one bacteria is cell enough to form 300 new viruses). After new viruses are formed, the wall of bacteria cell falls to pieces (lysis), the newly formed viruses get out and infect the other bacteria.

To better understand the lytic cycle of bacteriophage, study the figure below.

2. Lysogenic Cycle of Bacteriophage

In this cycle, the DNA of viruses only attaches itself on the DNA of bacteria. The DNA of viruses sticking on the DNA of bacteria is called prophage. Lysogenic cycle occurs if bacteria have immunity so the virus becomes not invirulent.

The DNA of viruses is entered into bacteria cells but formation of the parts of virus body does not happen. If the bacteria reproduce divide than selves the prophage also  divides so that every bacterium resulting from the division contains prophage. If the bacteria immunity system is lost, the prophage will become virulent and the bacteria will fall to pieces (lysis) because new viruses (prophage) are formed. Consefuently, lysogenic cycle can change into lysis cycle if the surrounding changes and the immunity of bacteria decreases.

To better understand the lysogenic cycle of bacteriophage, study the figure below.

Characteristics of virus

Characteristics of virus

Viruses have the characteristics as follows :

1. Viruses have 2 phase of existence, in their host cells and outside the host cells. If they are in their host cells, viruses can be called as organisms because they are able to reproduce, while if they are outside the host cells, viruses are not living.

2. Viruses can not be included in 1 of the kingdoms in classification system of the 5 kingdoms.

3. All viruses have parasitic characteristic and are harmful for their host.

4. Viruses consist of nucleic acid and capsid. Viruses with their mature parts are called virions.

5. Each virion consists of a type  nucleic acid (only DNA or RNA) and capsid. The nucleic acid generally only forms a single chain.

6. The size of viruses is extremely small with the diameter of about 20-400 nanometers (1 nanometer = 10^-9meters), so viruses can only be seen by using electron microscope.

History of Virus Inventions and Researches

History of Virus Inventions and Researches

The virus inventions and researches have gone through a long history involving many scientists. Although the virus inventions have been made continuously, the knowledge about viruses had only developed after finding of electron microscope.

Viruses have the size smaller than the smallest size of bacteria. Viruses have average diameter of about 20-400 nanometers (1 nanometer = 10^-9meters). Hence, viruses can only be seen with electron microscope. Electron microscope can enlarge the object until 200.000-400.000 times.

Although the virus structure was only known after the finding of electron microscope, long before that, scientists had conducted the researches on viruses. The scientists are as follows :

1. Edward Jenner (1749-1823)

Edward Jenner (1749-1823). He was the first scientist who succeeded in finding the preventive vaccine of smallpox (variola). Smallpox (variola) is caused by viruses.

 
2.  Louis Pasteur

Louis Pasteur. He was a French scientist who succeeded in finding that the center of disease infection at the brain and medula spinalis. Besides that, he also could transfer the infection to experimental animals in the laboratory.

3. D.J. Ivanovsky (1852)

D.J. Ivanovsky (1852). He was a Russian botanist who succeeded in extracting something from tobacco that had caught mosaic disease. Later, filtering the extract through a filter with the very fine pores hoping to be able to catch all existing bacteria,yet it turned out that the extract was still able to infect other tobacco leaves.

4. Adolf Meyer (1870-1885)

Adolf Meyer (1870-1885). He was a German microbiologist who succeeded in finding the yellow spots (mosaic) on tobacco leaf. According to him, the disease could infect other tobacco plants. To prove his analysis, he later spray the sap of the ill plant to a healthy one, apparently the healthy one becamed infected by the disease ( his analysis proven)

5. Loffler and Frosch (1897)

Loffler and Frosch (1897). They were German scientists who succeeded in finding the viruses attacking animals where the viruses caused foot an mouth disease to the animal.

6. Martinus Beijerink (1897)

Martinus Beijerink (1897). He was a Dutch microbiologist who succeeded in finding the fact that the organism of tobacco attacker could reproduce on the plant it lived on, but could not be reared in the medium of growth. Another fact which he found was that the organism did not die when it was put into alcohol. Based on the fact, finally he concluded that dilution from tobacco disease contained the organism called virus.

7. Reed (1900)

Reed (1900). He succeeded in finding the virus causing dengue disease in human being. This disease is propagated by Aedes aegypti mosquito as its medium.

8. Twort and d'Herelle (1916-1917)

Twort and d'Herelle (1916-1917). They succeeded in finding the viruses attacking bacteria. These viruses could cause decomposition (lysis)

9. Wedell Stanley (1935)

Wedell Stanley (1935). He was a biochemist from the Institute of Rockefeller, America, who succeeded in crystalizing TMV  and indicated that the crystal consistanly could maintain their infection ability. It was hard to imagine that this could be conducted to organisms. From that time on, the researches on viruses have kept developing.

10. Laidraw and  Stuart Harris (1933-1936)

Laidraw and  Stuart Harris (1933-1936). They succeeded is finding the influenza virus. They also concluded that if viruses were repeatedly put into experimental animal, it could influence their capacity to attack human being.

 
11. Jonas Salk (1953)
Jonas Salk (1953). He succeeded in finding the preventative vaccine for the polio disease.