Полнотекстовый поиск:
Где искать:
только в названии
только в тексте
слова в тексте
только заголовок

Рекомендуем ознакомиться

Остальные работы->Реферат
The image of the American family looks and functions very differently than families of the past few decades. Men and women raised in the 1950?s and 19...полностью>>
Остальные работы->Реферат
The Sibling Society by Robert Bly is a moving call for the rediscovery of adulthood. It is not about siblings in a family. Robert Bly has used the ter...полностью>>
Остальные работы->Реферат
Imagine yourself in the midst of the end of WWII, out in the streets of Stalingrad where Joseph Stalin will be parading. The masses of people seem to ...полностью>>
Остальные работы->Реферат
After reading Joyce Carol Oates story, ? The Night Nurse,? revenge is what is found. This story starts off by a woman by the name of Grace Burkhardt, ...полностью>>

Главная > Реферат >Остальные работы

Сохрани ссылку в одной из сетей:

Bacteria Essay, Research Paper


Bacteria are one celled organisms that are found almost everywhere. Bacteria live in soil, air, water and food. They also live in and on plants and animals. Bacteria can be found on our bodies in places such as our noses, mouths and intestines. Most bacteria measure from 0.3 to 2.0 microns in diameter. This means that bacteria can only be seen through a powerful microscope. Bacteriology is the study of bacteria. Some kinds of bacteria are helpful. Other kinds of bacteria can cause serious disease. Bacteriologist study harmful bacteria to determine how they cause disease so that vaccines can be developed.

Certain kinds of bacteria are helpful to humans. Bacteria help in digestion in both humans and certain animals such as cattle and horses. Bacteria help break down food and also furnishes vitamins. Bacteria are important in certain kinds of foods such as vinegar and certain types of cheese and in sauerkraut. Bacteria can also help to decompose dead organisms and animal wastes into chemical elements.

Certain kinds of bacteria are harmful to humans, animals and plants. Some kinds of bacteria can cause diseases in human beings. These diseases include tuberculosis, typhoid fever, meningitis, leprosy, cholera and certain types of

Page 2

pneumonia. Bacteria can also cause diseases in animals such as anthrax. Plant

diseases caused by bacteria are fire blight ( in pear and apple trees) Citrus canker, tomato and potato wilt. These crop diseases can result in tremendous financial

losses for farmers worldwide.

Bacteria reproduction is largely asexual. Most bacteria reproduction is by fission which is a process of cell division in which one bacterium splits into two new ones. Fission may occur every 15 to 20 minutes under particularly favorable conditions of temperature, moisture and food supply. Within an estimated 24 hours, a cholera bacterium could produce an enormous number of offspring weighing more than 2,000 metric tons. This is only theoretically possible because there would not be nearly enough space and food for this large number of offspring. There are many parts of a bacteria cell. Nearly all bacteria have a protective layer called the cell wall. The cell wall also gives the cell it s shape and enables it to live in a wide range of environments. Another part of the cell is the capsule. The capsule is a slimy layer outside the cell wall. The capsule protects the cell by making the cell resistant to chemicals that can hurt it. All bacteria have a cell

Page 3

membrane, an elastic, bag like structure just inside the cell wall. Small molecules

of food enter the cell through pores in the membrane. Inside the membrane is cytoplasm, a soft jelly like substance. The cytoplasm contains many chemicals

called enzymes, which help build cell parts and break down food. Like all living things, bacteria cells contain DNA (deoxyribonucleic acid) which controls the

cells growth, reproduction and all other activities. The DNA can be found in the nucleus body in all organisms except blue- green algae. DNA is also in the nucleus, a part of the cell separated from the cytoplasm by a membrane.

There are four types of bacteria cells. Scientist usually divide bacteria into four groups according to the shape of the bacteria. Round bacteria are called cocci. Rod shaped bacteria are called bacilli. The type of bacteria that looks like bent rods are called vibrios. Spirilla is the type of bacteria that is shaped like a spiral. Two are more bacteria can link together and these combinations are described by using different prefixes. Some of the prefixes are: diplo (pair), staphylo (cluster) and

strepto (chain). An example of linked bacteria is streptococci which is round bacteria that are linked together.

Page 4

Most bacterial diseases can be prevented by vaccines. Vaccines are made in different ways depending on what kind of bacteria causes the disease. There are three main types of vaccines. One type is made from live bacteria. The second type is made from killed bacteria. The third type of vaccine is made from inactivated poisons produced by the bacteria. Certain pathogenic bacteria become harmless after they have been grown for a while in the laboratory. When these harmless living bacteria are injected into animals the animals become immune to the disease caused by the strain of bacteria. In the United States, most vaccines that are used to prevent tuberculosis contain living but harmless bacteria. Killed bacteria of certain strains can be used for vaccines. Most Americans are vaccinated against whopping cough with bacteria that has been killed with heat or chemicals. Certain bacteria cause serious diseases because they produce powerful toxins. Vaccines to prevent some of these diseases can be prepared by growing the bacteria in the Laboratory, isolating the toxins they produce, and inactivating the toxins with heat or chemicals. Most Americans are vaccinated against diphtheria and tetanus with vaccines made of inactivated toxins. Some bacteria can be controlled in ways other

Page 5

than vaccinations. Modern methods of treating sewage, preserving food, and purifying water have reduced the spread of certain bacterial diseases.

Bacteria has an interesting history. Simple forms of bacteria were probably some of the first living things on earth. Fossils of bacteria have been found that are more than three billion years old. Some scientists believe that multi celled organisms gradually developed from certain bacteria.

Anton van Leeuwenhoek was the first scientist to see bacteria in 1676. He was a Dutch scientist. Back then, scientists believed that bacteria came from nonliving things. Scientists believed this until Louis Pasteur showed that only living things can produce other living things. Louis Pasteur made many important discoveries in bacteriology. Scientists continue to make important discoveries today. The next phase of this report will be a science experiment using bacteria.

Page 6

Science Fair Project on Bacteria

PROBLEM: Bacteria is everywhere in our school. What should we use to clean Lake Travis Middle School?

STATEMENT: Which is the best product to use to clean our school?

HYPOTHESIS: I think Mr. Clean will be the best product to clean our school.

MATERIALS: The materials used for this project were: prepared petri dishes, toothpicks, tin can, foil, Lysol, Mr. Clean and paper towels.

PROCEDURE: Put about ten toothpicks in a can and cover it with aluminum foil. Place the can in the oven and bake it for one hour at 250 degrees. This is to sterilize the toothpicks. Allow the toothpicks and can to cool. Scrape the toothpick on commonly touched surfaces in the school such as the bathroom door handle and the library door

Page 7

handle. Then rub the toothpick on the prepared surface in the petri dish. I let the bacteria clusters grow for two weeks. I then cut ten half circles of paper towels the same size as the petri dish. I soaked five of the half circles in Lysol and five of the half circles in Mr. Clean. One half circle was placed in each petri dish. I then let the paper towel remain in the petri dish for two weeks. I would check the paper towels to see if they needed to be re-moisten and I would re-moisten them if needed. At the end of the two week period, I then examined the petri dishes to see which product killed the bacteria the best.

RESULTS: Both of the products killed the bacteria, however, Lysol

appears to have a greater effect on killing the bacteria.

CONCLUSION: In reading the list of ingredients on both the Lysol and Mr. Clean container, I found that Mr Clean contains Cleaning agents ( nonionic and anionic surfactants) Page 8

quality control agents, perfume, colorant and water. The Lysol label states that Lysol contains 2.70% Alkyl 50%C14, 40% C12, 10% C16) dimethyl benzyl ammonium chlorides, and 97.3% Inert Ingredients. The following is a discussion of the ingredients found in Lysol. When hydrochloric acid is added to ammonium hydroxide it produces a solution called ammonium chloride. Another name for benzene is benzol. Benzol is often used in detergents. The ingredient dimethyl in the Lysol is formed from

methanol which is often used as a solvent to dissolve other substances.

The ingredients in the Lysol seemed to be stronger

in killing bacteria than the ingredients in Mr. Clean.

Загрузить файл

Похожие страницы:

  1. Bacteria Essay Research Paper Bacteria live almost

    Реферат >> Остальные работы
    Bacteria Essay, Research Paper Bacteria live almost everywhere, even ... in sanitized places. Some bacteria need oxygen to survive, ... a tails or antennas. Bacteria reproduces when one of them ... would die. Some diseases that bacteria makes are cholera, gonorrhea, ...
  2. Bacteria Essay Research Paper Enterobacter AerogenesIdentifying bacteria

    Реферат >> Остальные работы
    Bacteria Essay, Research Paper Enterobacter Aerogenes Identifying bacteria may seem like a ... The objective assigned to each individual in Dr. ... definitive identity for my bacteria. The deciding test would ... meningitis. Identifying my bacteria was not an easy ...
  3. Bacteria Essay Research Paper True cells

    Реферат >> Остальные работы
    Bacteria Essay, Research Paper True cells with a wall ... comprising a single, circular strand Bacteria may have plasmids = a circle ... which can move between bacteria. These may contain ... are photoautotrophic Bacteria reproduce by binary fission Bacteria are a ...
  4. Coliform Bacteria Essay Research Paper Coliform bacteria

    Реферат >> Остальные работы
    ... Bacteria Essay, Research Paper Coliform bacteria are good indicator organisms for the presence of pathogenic bacteria ... fermenting bacteria N/A N/A Table 1. Results from the stages for each sample ... tested. Coliform bacteria are gram- ...
  5. FleshEating Bacteria Essay Research Paper Some call

    Реферат >> Остальные работы
    Flesh-Eating Bacteria Essay, Research Paper Some call it ... multiplying aerobic and anaerobic bacteria are burrowing through soft ... of the Group A strep bacteria include: necrotizing fasciitis, which ... each other. After reading several articles and doing research ...

Хочу больше похожих работ...

Generated in 0.0015230178833008