Jon+Chu

Jonathan Chu Lab Science 9 Planning an Experiment- growth of bacteria/mold

Question for investigation: In what temperature(s) do bacteria grow best in?

Independent variable: the temperature in which the bacteria is to be grown in. This will be measured by a thermometer.

Dependent variable: the size and amount of the bacteria. This will be measured with a ruler.

Variables held constant: the amount of bacteria initially wiped onto the plate.

List of materials: l Cotton swabs l Plate to wipe bacteria in l Thermometers l A ruler

Sketch of Setup:

Procedure: 1. find a place where you suspect that there are bacteria present, this could be any place ranging from pencils to the insides of your fingernails. 2. get three cotton swabs and wipe the swabs on the place where you suspect has bacteria. 3. wipe the three swabs on three separate plates. Try to wipe it so that the three plates have an equal amount of area wiped. 4. put the covers on the three plates and place one of them in a sunny and warm area, one in a dark and colder area, and one in a place with room temperature. 5. leave the plates alone for one week while recording the temperature with the thermometer. 6. after a week take back the plates and compare the size of the bacteria on the plates. Measure with a ruler. **Warning: do not lick or hold the bacteria too close to your nose**

Expectations: I expect that the bacteria in the sunny and warm area will grow the most. I think this way because you often see lots of moss on rocks in sunny beaches, rivers, and such.

The results of this experiment might end up being the same on all three plates. If this happened then my guess is that the temperature difference between the three areas is not great enough to make a huge difference.

Jonathan Chu


 * Biology Experiment**
 * Killing Bacteria with** **Different Substances**


 * Goal:** to find out if certain things, such as soap and toothpaste, are able to either kill or to prevent the growth of bacteria.

Bacteria has affected the course of human history, this is a statement beyond doubt. Throughout human history, different bacteria have had many different roles. Sometimes bacteria kill people. Sometimes it helps our digestive systems, and sometimes it is used as medicine, such as penicillin. In our experiment we will expose the bacteria to different substances and to see if the substances can kill the bacteria. This relates to the pharmacy companies who create medicines that can kill harmful bacteria in your body.
 * Relevance:**

General Expectations: I expect that some of our substances will be able to show some visible evidence of bacteria being killed; such as disappearing bacteria colonies or colonies changing color.


 * Materials:**
 * Agar dishes
 * Microscope
 * Soap
 * Shampoo
 * Toothpaste
 * Sodium hydroxide
 * Perfume
 * Bleach
 * Mouthwash
 * Salt water
 * Tap Water
 * Alcohol
 * Hydrogen Peroxide-first aid antiseptic spray
 * Alcohol Swabs-70% isopropyl alcohol
 * Ethyl alcohol
 * Hand Sanitizer

Independent Variable: The independent variable would be the substance exposed to the bacteria

Dependent Variable: The dependent variable would be the bacteria after being exposed to the substance.


 * Procedure:**
 * 1) scrape bacteria on each agar plate, the bacteria should come from the same source. (refer to diagram 1)
 * 2) store all of the agar plates in the same place. Have them grow for the same amount of time
 * 3) after you’re done cultivating the bacteria, take them out and record what the bacteria in each plate looked like
 * 4)  expose each plate to a different substance. Methods of exposure varies from each substance from another, such as spraying antiseptic spray and dripping soap into plate. (refer to diagram 1)
 * 5) open up the plate again after a few days, record the appearance of the bacteria. Compare and contrast your observations from those before exposing the bacteria to the substance
 * 6) carefully scrape off parts of the agar with bacteria growing on it, observe it under the microscope

Diagram 1. Scraping the bacteria onto the agar plate Diagram 2. Exposing the bacteria to a substance.

Second Procedure: 1. Scrape bacteria onto the agar plates. Try and have bacteria that come from the same source. 2. after scraping the bacteria onto the agar plates, expose the bacteria to the substance. Keep one or two agar plates unexposed (as control plates) so you can compare the amount of bacteria later on. 3. tape up the agar plates with double layers of plates and leave it for a few days. 4. after a few days check on the agar plates to see if any bacteria have grown on any of the plates.


 * Expectations:**

Expectations for 1st procedure: I expect that bacteria disappear or change color when they die.

I expect that the sodium hydroxide, which is a strong acid and is highly corrosive, will kill all the bacteria along with the entire agar. I expect this because something as acidic as sodium hydroxide, which can easily dissolve certain metals and destroy our skin in contact, should also be able to kill bacteria and dissolve agar.

I expect that substances that are used daily to kill germs and bacteria, such as toothpaste, mouth wash, and hand sanitizers, should be able to kill bacteria. Especially the hand sanitizers since many of them claim to be able to kill 99% of all the bacteria on your hands.

Expectations for 2nd procedure:

I expect that the hand sanitizer should be able to prevent the growth of bacterial colonies. Seeing how they claimed to be able to kill 99% of the germs and bacteria on your hands.

I expect that the salt water would be able to prevent some growth of bacteria, but not all. I expect this because our salt water did not reach the state of a saturated solution.

=Results=

All the photos we have are from our second procedure.

Bac1. bacteria exposed to ethyl alcohol

Bac2. a control plate.

Bac 3. bacteria exposed to hand sanitizer.

Bac 4. bacteria exposed to salt water

Bac 5. 2nd control plate.

All observations involving a microscope are conducted with a 10X/0.25-160/0.17
 * Observations:**

We started off our experiment according to our procedure. We took plates of agar that already had bacteria growing colonies and exposed each of them to a different substance. Then we used taped and taped the agar plate in hopes of preventing unwanted things getting in, such as other bacteria in the air, and to prevent things from leaking out.

When we checked the agar plates during the next science class, we realized that we had no idea how to differentiate dead bacteria from live bacteria. In several of our plates, colonies of bacteria had turned black. From the pictures of penicillin killing bacteria we found online, the dead bacteria were white.

The entire agar and the bacteria growing on it were dissolved in the plate with sodium hydroxide. From this we can clearly that sodium hydroxide is able to kill bacteria.

Due to how we could not determine how to differentiate dead bacteria to live bacteria, we couldn’t go on with our original procedure.

After much thought, we decided to take another direction in our experiment. This time instead of trying to have the substances kill already growing bacteria colonies, we would wipe bacteria onto the agar and then expose it to the substances without allowing it time to grow into colonies. (Refer to “Second Procedure”)

We prepared two control plates in which no substance was exposed to them so we could compare the amount of bacteria growth between that with a substance and one without.

When we checked the plates after a few days, we found that the one control plate had numerous bacteria colonies growing. The plate exposed to the hand sanitizer had no sign of visible bacterial colonies. The plate exposed to ethyl alcohol had one bacteria colony growing.

Control Plates: (Bac 2 and Bac 5) Numerous amounts of bacterial colonies.

Plate Exposed to ethyl alcohol: (Bac 1) Numerous amounts of bacterial colonies. Showed no sign of preventing the growth of bacteria or killing bacteria.

Plate Exposed to salt water: (Bac 4) No sign of any bacterial life.

Plate Exposed to hand sanitizer: (Bac 2) No sign of any bacterial life.



Control 1 Control 2 Ethyl Alcohol Salt Water Hand Sanitizer After 2 days Several bacterial colonies Several bacterial colonies Several bacterial colonies No sign of any bacteria No sign of any bacteria After 4 days Numerous bacterial colonies Numerous bacterial colonies Numerous bacterial colonies No sign of any bacteria No sign of any bacteria

From what the results of our experiment showed, we can conclude that salt water and hand sanitizers are able to kill bacteria while ethyl alcohol cannot.


 * Discussion:**

First Procedure: The results of our first procedure were totally different from my expectations. Not only did no bacteria disappear, hardly any bacteria had a significant change of color either. In fact many bacteria continued to grow as if the substances were nothing at all.

Another major problem we faced in our first procedure was that we had no way to determine whether if the bacteria colonies were dead or alive. This leads to the question: How do you differentiate dead bacteria colonies from live ones? In an attempt to answer this question, we searched online for any articles that were relevant to this question. During our search Mr. Happer showed us a picture of penicillin killing bacteria. In that picture the dead bacteria turned white and parts of it seem to have disappeared. And seeing that none of the bacteria colonies in our plates turned white, we came to the conclusion that none of our bacteria colonies were killed by the substances.

Second Procedure: After seeing how our first procedure did not work out as we had planned, we created a second procedure in which it was a modification from the first.

In the 2nd procedure many of the results matched my expectations. Both the agar plates exposed to salt water and hand sanitizers had no sign of any bacterial growth. The plate exposed to ethyl alcohol, however, ironically had even more bacterial colonies than the control plates.

From how the plates exposed to salt water and hand sanitizer had no sign of any bacterial life, we concluded that both substances have the ability to kill bacteria. This leads to a question that could be answered by more experiments: Would salt water or hand sanitizers still be able to kill bacteria in a less concentrated form?

Below is a procedure I made that could be used to answer the above question: 1. prepare 5 cups with 40 ml of the substance inside 2. in one cup mix the substance with 10ml of water 3. in the second cup mix the substance with 20ml of water 4. in the third cup mix the solution with 30ml of water 5. in the fourth cup mix the solution with 40ml of water 6. leave the 5th up alone to be the control plate 7. take 5 agar plates and scrape bacteria from the same location onto each of them 8. expose the substances in each of the cups to a different plate 9. seal up the plates with tape or any other type of adhesive, try to make the pate as airtight as possible 10. wait for a few days


 * Appendix I Scientific Terminology:**

Agar is typically used in a final concentration of 1-2% for solidifying culture media. Smaller quantities (0.05-0.5%) are used in media for motility studies (0.5% w/v) and for growth of anaerobes (0.1%) and microaerophiles.
 * Agar:** a phycocolloid extracted from a group of red-purple marine algae (Class Rhodophyceae) including //Gelidium//, //Pterocladia// and //Gracilaria//. //Gelidium// is the preferred source for agars. Agar is a gel at room temperature, remaining firm at temperature as high as 65°C. Agar melts at approximately 85°C, a different temperature from that at which it solidifies, 32-40°C. Agar is generally resistant to shear forces; however, different agars may have different gel strengths or degrees of stiffness.

Origin: 1885–90; < Malay //agaragar// seaweed from which a gelatin is rendered, or the gelatin itself

We cultivated the bacteria in agar plates.

peptidoglycan.
 * Bacteria**: domain of unicellular prokaryotes that have cell walls containing

1847, from Mod.L. pl. of bacterium, from Gk. bakterion "small staff," dim. of baktron "stick, rod," from PIE *bak- "staff used for support." So called because the first ones observed were rod-shaped. Introduced as a scientific word 1838 by Ger. naturalist Christian Gottfried Ehrenberg (1795-1876).

In our experiment our goal is to see if certain substances are able to kill bacteria.


 * Ethyl Alcohol:** aka ethanol, An alcohol obtained from the fermentation of sugars and starches or by chemical synthesis. It is the intoxicating ingredient of alcoholic beverages, and is also used as a solvent, in explosives, and as an additive to or replacement for petroleum-based fuels. Also called //ethyl alcohol, grain alcohol. Chemical formula:// **C2H6O**

Medieval Latin, //fine metallic powder, especially of antimony//, from Arabic :, //the// + , //powder of antimony//; see  in Semitic roots

Seeing that ethyl alcohol is often used for sanitary means, I thought that it would be a good substance to test on the bacteria.


 * Hydrogen Peroxide:** a colorless, unstable, oily liquid, H2O2, an aqueous solution of which is used chiefly as an antiseptic and a bleaching agent.

Hydrogen- hydro: water, gene: create. Peroxide- per: very, oxide: oxygen

While brainstorming for ideas, we thought that antiseptics, such as hydrogen peroxide, should be able to kill bacteria.


 * Isopropyl Alcohol:** a colorless, flammable, water-soluble liquid, C3H8O, produced from propylene by the action of sulfuric acid and hydrolysis: used chiefly in the manufacture of antifreeze and rubbing alcohol and as a solvent.


 * Microscope:** an optical instrument having a magnifying lens or a combination of lenses for inspecting objects too small to be seen or too small to be seen distinctly and in detail by the unaided eye.

Micro-small, scope-to looks at

In hopes of finding a way to differentiate between living and dead bacteria, we looked at the bacteria under a microscope.


 * Penicillin:** any of several antibiotics of low toxicity, produced naturally by molds of the genus //Penicillium// and also semisynthetically, having a bactericidal action on many susceptible Gram-positive or Gram-negative cocci and bacilli, some also being effective against certain spirochetes.

Penicill-any fungus of the genus //Penicillium,// certain species of which are used in cheesemaking and as the source of penicillin, ium-suffix, chemical element or group

In order to give us an idea of what dead bacteria might look like, Mr. Happer showed us pictures of penicillin killing bacteria.


 * Peptidoglycan:** A polymer found in the cell walls of prokaryotes that consists of polysaccharide and peptide chains in a strong molecular network. Also called //mucopeptide//, //murein//.

peptide + glycan, //a polysaccharide//.

Prokaryotes, such as bacteria, have peptidoglycan in their cell walls.


 * Soap:** a substance used for washing and cleansing purposes, usually made by treating a fat with an alkali, as sodium or potassium hydroxide, and consisting chiefly of the sodium or potassium salts of the acids contained in the fat.

Origin: bef. 1000; ME //sope,// OE //sāpe,// c. G //Seife,// D //zeep,// all < WGmc (perh. ≫ L //sāpō;// cf.

I thought that it would be interesting to see if the soap in our school is really able to kill bacteria.


 * Sodium Hydroxide:** a white, deliquescent, water-soluble solid, NaOH, usually in the form of lumps, sticks, chips, or pellets, that upon solution in water generates heat: used chiefly in the manufacture of other chemicals, rayon, film, soap, as a laboratory reagent, and in medicine as a caustic.

Sodium- Na, Hydro- water, oxide-oxygen

We found that the sodium hydroxide we exposed to the agar completely dissolved the agar.


 * Expose:** to lay open to danger, attack, harm, etc.

Origin: 1425–75; late ME //exposen// < OF //exposer,// equiv. to //ex-// ex-1 + //poser// to put (see pose1), rendering L //expōnere// to put out, expose, set forth in words; see expound

Our experiment is centered on exposing bacteria to different substances to see if the substances are able to kill bacteria.


 * Airtight:** preventing the entrance or escape of air or gas

Air + tight- firmly closed

The fact that our agar plates weren’t airtight might’ve affected the outcome of our experiments.


 * Antiseptic:** free from or cleaned of germs and other microorganisms

Anti-agaisnt + septic- pertaining to or of the nature of sepsis; infected

Antiseptic sprays are often sprayed onto your skin when you get cut.


 * Immunity:** the state of being immune from or insusceptible to a particular disease or the like, the ability of a cell to react immunologically in the presence of an antigen

Immune- protected from a disease or the like, as by inoculation + ity- a suffix used to form abstract nouns expressing state or condition

Seeing that none of the bacteria in our agar plates seemed to be dying, Jeremy suggested that the bacteria might’ve become immune to the substance.


 * Antigen:** any substance that can stimulate the production of antibodies and combine specifically with them

Anti- against + gen-produce

Without antigens, our body would be a lot more vulnerable to diseases and bacteria.


 * Tape:** a strip of cloth, paper, or plastic with an adhesive surface, used for sealing, binding, or attaching items together; adhesive tape or masking tape

Origin: bef. 1000; ME; unexplained var. of //tappe,// OE //tæppe// strip (of cloth), lit., part torn off; akin to MLG //teppen// to tear, pluck

In order to make the agar plates as airtight as possible, we taped the agar plates with two layers of plate.


 * Acid:** a compound usually having a sour taste and capable of neutralizing alkalis and reddening blue litmus paper, containing hydrogen that can be replaced by a metal or an electropositive group to form a salt, or containing an atom that can accept a pair of electrons from a base. Acids are proton donors that yield hydronium ions in water solution, or electron-pair acceptors that combine with electron-pair donors or bases.

Origin: 1620–30; < L //acidus// sour, akin to //ācer// sharp, //acétum// vinegar, [|acescent], [|acicula]

We stopped using acid to kill the bacteria after seeing how the sodium hydroxide dissolved the entire agar.


 * Salt:** a crystalline compound, sodium chloride, NaCl, occurring as a mineral, a constituent of seawater, etc., and used for seasoning food, as a preservative, etc

Origin: bef. 900; (n. and adj.) ME; OE //sealt;// c. G //Salz,// ON, Goth //salt;// akin to L //sāl,// Gk //háls// (see [|halo-]); (v.) ME //salten,// OE //s//(//e//)//altan;// cf. OHG //salzan,// ON //salta////,// D //zouten//

In our experiment the salt water prevented all visible growth of bacteria.


 * Dissolve:** to make a solution of, as by mixing with a liquid; pass into solution: to dissolve salt in water

Dis- a Latin prefix meaning “apart,” “asunder,” “away,” “utterly,” or having a privative, negative, or reversing force, solve- to find the answer or explanation for; clear up

Since we couldn’t sprinkle salt onto the bacteria as a substance, we dissolved the salt in water to make salt water.


 * Alcohol:** a colorless, limpid, volatile, flammable, water-miscible liquid, C2H5OH, having an etherlike odor and pungent, burning taste, the intoxicating principle of fermented liquors, produced by yeast fermentation of certain carbohydrates, as grains, molasses, starch, or sugar, or obtained synthetically by hydration of ethylene or as a by-product of certain hydrocarbon syntheses

Origin: 1535–45; < NL < ML < Ar //al-kuḥl// the powdered antimony, the distillate

We thought that since people wipe alcohol onto cuts and scrapes alcohol might be able to kill bacteria.


 * APPENDIX II (Key Concepts)**

=Bacteria Reproduction=

Most bacteria reproduce through means of binary fission. In binary fission it is almost as if the bacteria creates a clone of itself. First the bacterium grows until it has doubled its size, then it replicates its DNA and then splits into two halves. Thus creating another one identical bacterium. (Refer to BR1) BR1. A simple diagram of the process of binary fission.

Bacteria that don’t reproduce by binary fissions often produce by conjugation. Unlike binary fission where the bacterium reproduces asexually, in conjugation there needs to be two bacteria. The two bacteria connect through a “bridge” and exchanges their genes.

The last way of reproduction of bacteria is spore formation. Like how soldiers hide in bunkers when they are in danger, some bacteria form structures called spores when they are in danger too. And like the soldiers in the bunkers, the bacterium waits until the danger is away and then comes out to grow again. These tough spores can often remain dormant up to many months and even years.

=Bacteria/Bacteria Structure= Bacteria are microscopic prokaryotes that are usually 0.3 to 2 micrometers. Bacteria have a cell wall and a cell membrane, which protects the inside of the bacteria which include the DNA and the ribosome. Different bacteria have different ways of moving, such as how the bacteria //E.coli// have flagella to propel itself forword.

=E. Coli= This is a diagram of the E.Coli Bacteria. The E. Coli bacteria has a cell wall and a cell membrane to protect the insides of the bacteria, which contains the DNA and the ribosome (which is not shown in the diagram) The flagellum are the “propellers” of the E. Coli and allows the bacteria to move.

Some bacteria produce their own food by photosynthesis while others decompose and break down nutrients around them. Bacteria have many roles in our world, which include maintaining the equilibrium of our environment by being decomposers and supplying plants with nitrogen. Humans have also put bacteria into great use, nowadays bacteria can be used to help us in many ways; bacteria can be made into food and beverages or used to make medicine.

=Characteristics of Acids= Substances that have a PH level below 7 are considered acidic. Acids have four major characteristics. 1. All acids taste and smell sour. Lemons are a perfect example. 2. Litmus papers turn into a reddish color when exposed to acidic substances 3. Acids negates bases 4. acids react with metals to form salts

Many stronger acids, such as sodium hydroxide, are very corrosive. Such strong acids can easily dissolve agar and are extremely dangerous.


 * References:**

http://static.howstuffworks.com/gif/cell-ecoli.gif

Miller KR, Levine JS. //Biology.// Upper Saddle River, New Jersey: Prentice Hall; 2006: 471-477.