| The Effectof Various Disinfectants on Bacteria | |
 Researched by Charley W. |
Purpose
The purpose of this experiment was to determine which disinfectant wouldmost effectively kill bacteria.
I became interested in this idea when I was washing the counter andI wondered if the disinfectant I was using was better than another was.
The information gained from this experiment would help parents, healthcare providers, and food preparers to know which disinfectant to use tothe best results for killing bacteria.
Hypothesis
My hypothesis was that bleach would work the best in killing the bacteria.
I based my hypothesis on Marie Clark, Microbiologist at Memorial Hospital,who said, "Bleach will probably work the best because it is an oxidant."
Experiment Design
The constants in this study were:
- The amount of disinfectant used
- The type of agar plates used
- The way the number of live colonies were measured
- The temperature and time of incubation
- The incubator
- The number of organisms there were to start
- That the disinfectants were opened from a new bottle for the experiment
- The time the bacteria and disinfectant were in contact before plating
The responding variable was how many bacteria were killed by the disinfectantafter one night of incubation.
To measure the responding variable the percentage of surviving colonieswas determined.
Materials
| Quantity | Item Description |
| 40 | microliters Escherichia coli |
| 40 | microliters Staphylococcus epidermidis |
| 40 | microliters Staphylococcus aureus |
| 40 | microliters Enterococcus faecalis |
| 40 | microliters Pseudomonas aeruginosa |
| 40 | microliters Bacillus sp. (not anthrax) |
| 60 | microliters Lysol (from new bottle) |
| 60 | microliters Bleach (from new bottle) |
| 60 | microliters Krud Kutter (from new bottle) |
| 60 | microliters 409 (from new bottle) |
| 30 | Nutrient agar plates |
| 30 | Sterile loops |
| 30 | Sterile tubes |
| 1 | Pipette |
| 1 | Incubator |
Procedures
1. Culture several species of bacteria including:
a. Escherichia coli,
b. Staphylococcus epidermidis,
c. Staphylococcus aureus,
d. Enterococcus faecalis,
e. Pseudomonas aeruginosa
f. Bacillus sp. (not anthrax)
2. Using a 10% solution of one bacterial species, and dispense 100microliters into a sterile tube.
3. Dispense (by pipette) 10 microliters of disinfectant into tube ofbacteria.
4. Hold the mixture in the tube for 5 minutes.
5. Pipette 10 microliters of the mixture onto a nutrient agar plate.
6. Spread mixture with sterile loop to cover entire surface.
7. Incubate over-night at 35 degrees Celsius in air.
8. Use a percent to put down how many live colonies are on the plate.
9. Repeat steps 2-7 with the next type of disinfectant.
10. Repeat steps 2-8 with the next bacterial specie.
11. Repeat steps 2-9 with the control group (no adding of disinfectant.)
12. Record all data.
13. Auto-clave all materials used and wash hands.
RESULTS
The original purpose of this experiment was to determine which disinfectantwould most effectively kill bacteria.
The results of the experiment were that bleach worked the most effectivelyto kill bacteria.
See table and graphs.
CONCLUSION
My hypothesis was that bleach would work most effectively to kill themost bacteria.
The results indicate that this hypothesis should be accepted.
Because of the results of this experiment, I wonder if bleach wouldstill work the best if there were different types of bacteria used. I alsowonder if there would be different results if I tested more disinfectantsfor the experiment. I also wonder if one half or one tenth as much disinfectantwould show similar results.
If I were to conduct this project again, I would test more brands ofdisinfectants for the experiment. I would also use more types of bacteria,and I would do more than one trial for the each test to obtain more accurateresults and to get an average.
Research Report Introduction Health is one of the most important factors in human life. Contractingan illness can be bad, and can even cause death. Using a disinfectant thatwill effectively kill harmful bacteria can help people stay healthy.Bacteria Bacteria are "any of a large group of very small one-celled organisms thatreproduce by fission or by forming spores. Some kinds can cause disease,while others are active in fermentation." The American Heritage StudentDictionary, 1994 EditionBacteria are one-celled organisms that are classified as prokaryotes,meaning they have no nucleus. They are approximately 2-3 microns in diameter(a micron is 1/24,500 of an inch or 0.001 millimeters.) Bacteria are justabout everywhere, consist of about a thousand types, and can be eitherharmful or harmless. Types of Bacteria: There are 4 types of bacteria. Those with a round shape are called "cocci",the rod-shaped are "bacilli", the bent rods are "vibrios", and the spiralshaped are "spirilla" or "spirochetes". They can either live alone, orthey may live in a pair, which is called "diplo", a cluster, which is "staphylo",or a chain, which is "strepto".Bacteria can also be classified by whether they do or dont need airto live. If they do, they are called aerobic bacteria, or aerobes. If thebacterium can live without oxygen, it is call an anaerobic bacterium, oranaerobe. Harmless Bacteria: There are a lot of types of bacteria that help in everyday life. Bacteriathat live in the intestines help digest food, kill harmful bacteria cells,and break down nutrients the body needs to stay healthy. There are alsobacteria that live in soil and water, and they recycle carbon, nitrogen,sulfur, and chemical elements. Others break down dead organisms and animalwaste into chemical elements that plants and animals can use. Some bacteriamake fermentation possible, while others help clean the water at sewerplants. There are even some types of bacteria that help create medications,antibiotics, and drugs.Harmful bacteria: Out of thousands of types of bacteria, there are only a few that are harmful.These harmful bacteria get into the body system by openings like the nose,mouth, or cuts in the skin. They can cause disease like cholera, gonorrhea,leprosy, pneumonia, syphilis, tuberculosis, typhoid fever, and whoopingcough. Harmful bacteria are transmitted from person to person by air, food,or water. Bacteria can also get into plants and animal body systems. Theycan create diseases like anthrax in livestock (mostly cows and sheep),fire blight in fruit trees, soft rot in fruits and vegetables, and crowngalls in various different plants.Some bacteria that get into the body can make poisons and cause diseaseslike diphtheria, scarlet fever, or tetanus. These poisons may be givenoff while the bacterium is alive or dead. One type of harmful bacterialets out poisons in poorly canned foods and can create food poisoning calledbotulism. Once harmful bacterial cells get inside a persons body system,they make the body operate improperly, and can also create a weak immunesystem and turn healthy and harmless cells into harmful cells. Structure of Bacteria: "A bacterial cell may have up to three protective layers, these layerssurround the cytoplasm, which contains the cells nucleoid. Hairlike flagellaextend through the layers in many types of bacteria. The flagella helpthe bacterium to move by means of a whiplike motion." The World Book Encyclopedia,Volume 2 (B), 1998 EditionBacteria consist of a single cell. Some have a capsule on the outsideof their cell wall, which helps resist destructive chemicals. If thereis a capsule on the bacterium, it is outside of the cell wall. The cellwall gives the bacterium its shape and allows it to live in all types ofenvironments. The cell wall covers the cell membrane, which is an elastic,baglike structure. The cell membrane holds the cytoplasm, a soft, jellylikesubstance. This cytoplasm has lots of enzymes, which break down food andbuild cell parts. There may also be flagella on the bacterium. It may haveflagella on one end, both ends, or all over. They help the bacterium move.It also has the nucleoid, which is formed from the bacteriums deoxyribonucleicacid (DNA). The DNA controls the growth, reproduction, and all activitiesof the bacterium. Reproduction: To reproduce, bacteria use a process called binary fission. This processincludes the bacteriums chromosome duplicating, and the cell dividinginto two identical cells. This is why scientists and microbiologists dontreproduce bacteria for getting different genes. Higher organisms get andhave different genes because of the difference in their parents reproductivecells. Since bacteria have only one cell, and use binary fission to reproduce,they cannot have different genes or reproductive cells. They have theirDNA mixed by transformation, conjugation, or transduction. When a bacteriumsDNA is transformed, it means that they get DNA parts in soil or water asdead bacteria are decayed. If it is conjuguated, the donor hooks onto thereceiver, makes a pilus (tube), and gives their plasmid DNA parts to thereceiver. When a bacterium is transducted, there is a transfer of DNA partsthrough cells by a bacteriophage (a virus that infects). Doing any of theseto mix genes can give bacteria new traits. They can include withstandingacidity or temperature changes, and antibiotic resistance.Disease: There are only a couple of species of bacteria that cause disease out ofthe thousands of species that are living. Some of them are Yersina pestis,which caused plague. Plague was feared because it often resulted in widespreaddeath. Epidemics of plague have killed hundreds of millions of people.There is also Vibrio cholerae, the bacteria that causes cholera. This causedmany cholera epidemics in Europe and Asia in the 1800s, and thousandsof deaths. There was also a cholera epidemic in South America in the 1900s,which took about 6,000 lives.Mycobacterium tuberculosis, or the tuberculosis causing bacterium,is a big problem in the world. Streptomycin, the cure for tuberculosis,doesnt work anymore because of the overuse of antibiotics making resistantbacteria. There are also bacteria and viruses that cause forms of pneumoniaand strep throat. Pneumonia is a term for lung diseases including swelling,and strep throat is a disease that affects the throat and tonsils. History: Antoni van Leeuwenhoek made microscopes in Holland during the late 17thcentury. He was the first person to study bacteria and worked hundredsof hours to make ground glass lenses for his microscopes. A lot of peoplesay that he was the founder of microbiology. Leeuwenhoek was the firstperson to discover bacteria as well as study them.Louis Pasteur proved that microbes dont come from dead matter, andRobert Koch proved that bacteria are disease causing. Sergei Winogradskyexplained about enery-yielding metabolic reactions and found out that therewere anaerobic microorganisms. Martinus Beijerinck found out microorganismshelp cycle nutrients like nitrogen. Selman Waksman discovered that bacteriain soil made antibiotics. Lynn Margulis showed the prokaryotic nature ofeukaryotes like plants and animals. Lynns studies made the hypothesisof endosymbiosis, which stated the "key eukaryotic features such as theenergy-generating centers called mitochondria in all animals, plants, andfungi and the photosynthesizing centers called chloroplasts in all algaeand plants were derived from ancient bacteria." (Microsoft Encarta 2001)Carl Woese discovered there is one bacteria, called archae bacteria, thatare prokaryotes and eukaryotes at the same time. Disinfectants A disinfectant is "a substance that kills microorganisms that cause disease."The American Heritage Student Dictionary 1994 EditionDisinfectants are liquid substances that kill germs or bacteria on non-livingobjects. They are usually chemicals used to clean clothes, rooms, dishes,and utensils. Disinfectants are often put into water and sewer systemsto help stop citywide diseases. They are also used to help hospitals andcare units stay clean and free of germs. The common disinfectants usedin households arent as effective as the ones used in hospitals or careunits to stop diseases. There are even some disinfectants that are largelyuseless and could be replaced with soap and water to do the job. There are seven main types of disinfectants. They include: Alcohols: There are two different types of alcohol disinfectants. There are ethyland isopropyl alcohols. These disinfectants are used to clean plastic andrubber. They also clean thermometers used to take a persons body temperature.Formaldehyde and Glutaraldehyde: Formaldehyde and glutaraldehyde are fast-acting disinfectants. They disinfectquickly and effectively. They are used mostly by hospitals to clean thesurgical tools and other medical devices.Hypochlorites: Hypochlorites are disinfectants that have chlorine bleach and chlorinatedlime, usual ingredients in disinfectants and deoderizers. They are usedto treat water and sewage systems and to clean eating utensils.Iodophors: Iodophors are disinfectants that include iodine. They are used to cleanhospital surfaces like tables and beds, and also to disinfect food preparationequipment.Phenols: Phenols are disinfectants that include carbolic acid, creosote, and hexachlorophene.They are used to clean floors, trash cans, bathrooms, and other large surfaces.Pine Oil Disinfectants: Pine oil disinfectants are mixed with detergents. They are most commonlyused to clean floors, walls, and bathroom fixtures, like toilets and sinks,and have a pine-like smell to them.Quaternary Ammonium Compounds: Quaternary ammonium compounds are used in lots of common household cleaners.They are used as disinfectants and as detergents.Conclusion Health is very important. Getting a sickness from bacteria can happen inan unhealthy environment. Using a disinfectant to kill harmful bacteriais an important way to stay healthy. |
Bibliography American Society for Microbiology "Bacteria" October 18, 2002 "Bacteria." Microsoft Encarta. 2001 edition. CD-ROM. Microsoft Corporation,1993-2000 Egmond, Wim van and Parmentier, Jan. "Bacteria." November 8, 2002. Facklam, Howard and Margery. Bacteria. Canada Twenty First Century Books1994 Rodowski, Jr., Christopher A. "Disinfectant" The World Book Encyclopedia.1995 vol. 5 (D) Schlessinger, David "Bacteria" The World Book Encyclopedia. 1999 vol.2 (B) "Whats a Microbe?." October 6, 2002 Todar, Kenneth University of Wisconsin-Madison Department of Bacteriology."Pseudomonas Aeruginosa" |
ACKNOWLEDGEMENTS
I would like to thank the following people:
- My mom for driving me to the hospital so I could do my experiment.
- Mr. Newkirk for correcting my journal, abstract, etc.
- Mrs. Helms for helping me with my board.
- The Memorial Hospital Microbiologist for helping me with my experiment.
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