SKATEBOARDING ON OLYMPUS MONS

 

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Microbiology for Kids

 

The series of experiments focuses on both the positive and negative aspects of microbes and addresses four major areas-evolution, environment, disease, and biotechnology. You don’t have to have an advanced scientific degree to demonstrate or do these activities. Anyone — parent, teacher, student, community group leader, scout troop leader, science club member, etc. — can lead these activities.

 

Creepy Critters

What if a new planet was discovered that had life on it? Would you be able to figure out what known creatures these alien life forms might be related to? What would you look for to compare? How would you organize these different living things?

 

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Scientists who study living things organize them into categories based on their relationships. Early classification systems were based simply on how things look. Now scientists focus on genetics, cellular make-up and other more specific things when they classify creatures.
Classification systems include big groups that are subdivided into smaller groups. Here's one way classification might work using cars as an example:

 

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Imagine it's the year 2525. A planet similar to Earth has recently been found in a newly identified solar system in another galaxy. We have sent a space probe with a molecular transport beam to this planet to beam back a variety of different living creatures. Scientists examine the structure of each of these creatures and realize that they need to create a classification scheme to help them compare the alien life forms to each other and discover how they might be related.
The lead scientist sends you illustrations of the organisms and asks you to help develop this classification system. Your role is to study the illustrations and come up with a possible classification scheme based on the information provided about each organism. You'll be asked to explain to the scientific team how and why you organized the creatures this way. Print out these pages and follow the directions to do this activity at home. When you're done, come back to this page to test your newfound knowledge by answering the questions below. (No fair peeking at the answers before you do the activity!)
Note: This activity will take 30 minutes to 1 hour.
You’ll Need:

Note: Be careful handling sharp scissors.
What To Do:
1. Click on the link above for critter cards pages. Print out each page and cut out the cards. Keep the last four cards separate from the others.
2. Study all the cards except the last four, noting similarities and differences among the creatures. Create a table on your paper to help organize what you see. You might have columns to describe bristles, antennae, eyes, etc. You might want to number your cards to help keep track of which you're describing.
3. Now put the cards (except the four you've kept separate) into groups based on the similarities and/or differences you see. Each group should include creatures that have something in common. Now create a new table, listing the traits common to each group you've made.
4. Choose one of the cards from the four you've kept separate. This is a picture of a creature was just beamed back by the space probe and sent to you by the lead scientist. You need to decide where it fits in the group system you've just created. Do you need to make a new group for this creature or can you find some way to fit it into one of your existing groups?
5. Write a brief paragraph explaining your classification scheme, how it works and how easy or hard it is to fit new creatures into it.
Questions

  1. Why do we classify things?  Answer
  2. Is your way the only way possible to organize the critter cards?  Answer
  3. Do you happen to know the biological classification scheme used by scientists who study living things?  Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

Biosphere in a Bottle

Think about the different places various kinds of plants and animal live. As you know, many, like penguins and cacti, can only live in certain places.
Now think about times you’ve dug a hole in the ground. Did you notice differences in the color of the soil layers? Did you wonder what causes those color differences?


 

Closeup of bottle

Lots of different kinds of bacteria make their home in the soil. Some are photosynthetic (foe-toe-sin-the-tick). Light provides the energy they need to grow. Photosynthetic microbes live in specific kinds of light. To some, too much light is as harmful to them as no light at all.
Different bacteria also need different amounts of oxygen. In mud, the surface area has lots of oxygen. Further below the surface, the mud lacks oxygen. Bacteria that need oxygen to live are called aerobic /air-oh-bick/ and live at or near the surface, while bacteria that don’t need oxygen are called anaerobic (an-air-oh-bick) and live deeper in the earth.
In this experiment you’ll explore some of the factors that determine where bacteria can live. Print out these pages and follow the directions to do this experiment at home. When you're done, come back to this page to test your newfound knowledge by answering the questions below. (No fair peeking at the answers before you've done the activity!)
Note: This is a long-term experiment. It will take 3-4 weeks for bacteria to grow before you can get full results.
You’ll Need:

What To Do:
1. Wash your hands before starting. (If you have a cut or wound, you should wear latex or rubber gloves when collecting and working with soil.)
2. Shred a sheet of newspaper into thin strips and set it aside.
3. In the 2-gallon bucket, add five or six cups of soil or mud from one of your collection buckets. Pick out all the sticks, leaves and pebbles. While stirring, slowly add water (collected from the same source) to the soil until your mixture becomes like thick cream. The amount of water you need to add will depend on how wet your soil is at the start. Add the shredded newspaper and one tablespoon of powdered chalk. Mix the contents gently. Make sure the mixture is wet enough that it will flow easily through the funnel.

 

© Eric MacDicken

4. Using masking tape, make a label for one jar or bottle with the name of the soil source on it (e.g. My Backyard). Using the funnel, pour approximately a half-inch of your mixture into the jar or bottle.

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© Eric MacDicken 

5. With one hand covering the opening of your jar and the other holding the base, gently tap the base a few times on a hard surface to allow the mixture to settle evenly. Continue to fill the jar, gently tapping the base every few inches, until it is filled to within two inches from the top. Close the lid or cover the bottle tightly with plastic wrap secured by rubberbands.

 

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6. Repeat the process to fill each of your jars/bottles with soil or mud collected from a different place. (Rinse out your 2-gallon bucket well in between mixing each new batch.) Be sure each new jar/bottle is labeled properly.
7. Place your jars/bottles in a well-lit place, but not in direct sunlight. If you wish, shine indirect light on the jars/bottles with your lamps. Keep them out of heat and at room temperature.

 

© Eric MacDicken

8. For three or four weeks, observe the jars/bottles daily looking for color changes in the mixtures. Record your observations in a notebook. Draw, label and color a picture of each of the jars at the end of each week.

 

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Questions

  1. Why are there different colors in the jars/bottles? Answer
  2. What causes the red, orange, green, white and black colors? Answer
  3. Why do some colors appear in one part of a jar/bottle and not another? Answer
  4. What would happen if you kept a jar/bottle in a dark closet? Answer
  5. What would happen if you left a jar/bottle in intense heat? Answer
  6. What would happen if you covered your jars or bottles with different colored plastic wrap? Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

 Bread Bag Nightmares

As you know, we keep food in refrigerators so it will last longer. But still, sometimes you open a bag of bread or a jar of spaghetti sauce and what do you find? Mold!!
Ever wonder exactly what mold is? And how did it get there? And why sometimes it’s green and other times black or white? Did you know this stuff is alive and growing?
In this experiment, you’ll find out all about those colorful, fuzzy fungi by growing your own crop. Print out these pages and follow the
directions to do this experiment at home. When you're done, come
back to this page to test your newfound knowledge by answering
the questions below. (No fair peeking at the answers before you do the activity!)
Note: This is a long-term activity. It will take several days for the mold to grow. The first day should take about 30 minutes to one hour. For safety reasons, don’t eat or drink while doing this experiment. And don’t taste or eat any of the materials used in the activity.
You’ll Need:

*It’s best if you use newly bought, fresh bread to make this experiment as accurate as possible.
Preparing sugar water
Note: Young people who don’t have experience operating a stove or microwave oven should get help and supervision from an adult. Parents or supervisors of young children may consider doing this step themselves.
Microwave: Stir 1/4 cup of sugar into 1/4 cup of water in a microwave-safe container and heat at one-minute intervals until sugar dissolves. Water will not need to reach boiling. Use potholders or oven mitts to handle container. Allow the mixture to cool for about five minutes before using.
Stovetop: Stir 1/4 cup of sugar into 1/4 cup of water in a small saucepan. Heat over medium heat until the sugar is dissolved. Use potholders to handle hot saucepan. Allow the mixture to cool for about five minutes before using.
What To Do:
1. Using masking tape and marker, make labels for four sandwich bags. Label the first bag "Dry White Bread." Label the second "Water on White Bread," the third "Lemon Juice on White Bread," and the fourth "Sugar Water on White Bread."

 

 

2. Wash your hands. Place a slice of white bread in the bag labeled "Dry White Bread" and seal the bag. Using one eye dropper, sprinkle 20 drops of tap water on another slice of white bread. (Don’t overdo it; the bread should be moist, not wet. If your bread is dripping, you’ve definitely done way too much. Throw away that slice and try again.) Place the moist bread in the bag marked "Water on White Bread" and seal the bag. Using a different eye dropper, sprinkle 20 drops of lemon juice on another slice of white bread and put it in the bag marked "Lemon Juice on White Bread" and seal the bag. Using your third eye dropper, sprinkle 20 drops of sugar water on the last slice of white bread and place it in the bag labeled "Sugar Water on White Bread" and seal. Try to keep your fingers off moist spots when handling each slice of bread.
3. Repeat steps 1 and 2, but this time use a different kind of bread in the remaining four bags. Your labels should note what kind of bread you’re using. Wash your hands when you’re done.
4. Make sure all of your bags are tightly sealed. Place all eight bags in a dark, warm place (about 86 degrees Fahrenheit, 30 degrees Celsius). Check with your parents or supervisor about where to store the bags. Check the bags each day for two weeks and record the results in a notebook. You may wish to draw or take pictures of the bread slices. Don’t open the bags!

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5. Make a graph recording the total growth of mold on each of the four white bread slices at the end of two weeks (see sample graph on right). Make a similar graph for the other four bread slices. Compare the results. At the end of the two weeks, throw out all the bags unopened.

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Questions

  1. From this activity can you tell what helps mold to grow best? Answer
  2. Does it matter what kind of bread you use? Answer
  3. What causes the different colors you see? Answer
  4. What would happen if you left the bags in a well-lit place instead of a dark place?Answer
  5. What would happen if you changed the temperature? Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

 Now You See It...Now You Don't!

Maybe you’ve heard the term "biodegradable." It basically means something capable of being broken apart into simpler substances by natural biological processes.
But what are these biological processes that break some things down? Why do some things biodegrade more readily than others?
In this experiment, you’ll investigate the biodegrading process of commercial packing peanuts. Print out these pages and follow the directions to do this experiment at home. When you're done, come back to this page to test your newfound knowledge by answering the questions below. (No fair peeking at the answers before you've done the activity!)
Note: This experiment will take you about 30 minutes to 1 hour to do on the first day, and about 10-20 minutes each successive day over five days.
You’ll Need:

What To Do:
1.  Wash your hands before starting.
2.  Lay the potato slice on your table. Using the eye dropper, put a drop of iodine at four separate locations on the slice and watch what happens. The resulting blue-black color is caused by a chemical reaction between the starch in the potato and the iodine. An iodine test like this is often used to confirm whether there is starch in a sample.
3.  Put a drop of iodine on a polystyrene peanut and a drop on a a biodegradable peanut and observe what happens. What does this tell you about the make up of each kind of peanut? Throw away the potato slice and peanuts and wash your hands.

 

© John Mier



4.  Using the masking tape, label your jars 1 through 6. Put 1/4 cup (50 mL) of aged water in each. Put one teaspoon of corn starch in jars 1 and 2. Clean your teaspoon. Put two biodegradable peanuts in jars 3 and 4 and two polystyrene peanuts in jars 5 and 6. Add one teaspoon of compost activator to jars 2, 4 and 6. Mix the contents of each jar, cleaning your stirring utensil between jars.

 

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5.  Test the contents from each of your jars for starch. Put five drops of the mixture from jar 1 in a test tube. Add a drop of iodine to the tube. Record the results. Repeat this procedure for each of the other jars. Be sure to rinse out your test tube thoroughly before testing the contents of the next jar or use a new eye dropper for each jar. Wash your hands when you finish this part of the experiment.

 

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6.  Each day for five days, retest the jars’ contents for starch and record the results. How long does it take for you to see a change? Be sure to wash your hands before and after completing the testing steps.


Questions

  1. Why does a polystyrene peanut not degrade the same way the starch peanut does?   Answer
  2. Are live bacteria necessary for breakdown?  Answer
  3. What would happen if you buried a polystyrene peanut and a starch peanut in your yard during the fall and dug up the spot in the spring?  Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

 Caught Dirty-Handed

When was the last time you washed your hands? Did you use soap? What have you done since you washed? Have you eaten, put your fingers in your mouth or touched someone else?
Observations in public restrooms have revealed that only about 68 percent of Americans wash up before leaving. Yet thorough hand washing is one of the best ways to prevent the spread of infections. There are millions of microbes on your hands. Most are naturally occurring and harmless. But some may be disease-causing germs. Hand washing with soap lifts off those microbes and rinses them away.
In this group activity, you and your friends or family members will test the effectiveness of different hand washing times, techniques and materials. Print out these pages and start scrubbing. Come back when you're done with the steps to test your newfound knowledge by answering the questions at the end of the experiment. (No fair peeking at the answers before you've done the activity!)
Note: You can do this whole experiment in one to two hours, depending on how many people take part.
You’ll Need:

 

© Eric MacDicken

What To Do:
1. Come up with scoring guide for hand cleanliness. Divide a piece of paper into four sections and trace an outline of a hand in each section. Use your pens or crayons to shade in your idea of completely dirty, very dirty, dirty and slightly dirty. Label the completely dirty hand as ++++, the very dirty hand as +++ and so on. Note that – stands for completely clean.
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© Eric MacDicken

 

 

2. Cover your workspace with newspaper. Pick one person to be the hand washer and one person to be the timekeeper. The washer should put about one teaspoon of washable paint on the palm of one hand and spread it evenly over both hands, including the backs of the hands and the skin next to and under the fingernails. Allow hands to dry completely—about a minute or two. Close the paint.

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3. Go to the sink where hand washer is blindfolded so the washer can’t see his/her hands. Turn on warm water. Have the washer wash with just water for one second. After one second, have the timekeeper blot dry the washer’s hands by very lightly touching the towel to the skin (don’t rub!). Don’t let the hand washer see his/her hands or give away any hints about how clean they are. Using the scoring guide you’ve created, record the cleanliness on a scoring chart. (See sample scoring chart below. This scoring chart should be labeled "Water Only")

 

© Eric MacDicken

4. Have the washer wash for four more seconds with just water. Again, lightly blot the washer’s hands and record their cleanliness.
5. Have the washer wash for fifteen seconds more with water. Once again, blot and record the cleanliness.

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6. Take the blindfold off and allow the washer to completely clean his/her hands. Put the blindfold back on and repeat steps 2 through 5, only this time have the washer use soap each time. Use a new scoring chart labeled "Water and Soap."
7. Change roles and repeat the activity until everyone taking part has had a turn being the handwasher. As much as possible, have the same person keep time and record cleanliness for each hand washer.
8. Display your results. Create two graphs showing the average cleanliness score at each time interval. One graph will show the results when handwashers used water only. The other graph will show results when they used water and soap. Put the time on horizontal line going across the page. Mark every number between 0 and 20 seconds. Put the average cleanliness scores on the vertical line.
Sample scoring chart:


Washer

Washing Time (in seconds) with Water Only

 

0

1

5

20

Margaret

++++

++++

++

+

Jose

++++

+++

++

+

Kiesha

++++

+++

++

-

Average

++++

+++

++

+

Questions

  1. How might hand washing affect your family’s health? Answer
  2. What difference does soap make? Answer
  3. What infectious diseases could be spread by failure of people to adequately wash their hands? Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

Let's Get Small

Just how small is a microbe? If you happen to read a report written by a microbiologist, you might learn that a poliovirus is 30 nanometers in diameter and that anE. coli cell is 3 micrometers long. But does that mean anything to you? Scientists use these measurement terms because microbes are so small, they cannot be measured using the more familiar inches or millimeters. (A micrometer is a thousand times smaller than a millimeter and a nanometer is one million times smaller than a millimeter.)

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If you read What is a Microbe, you came across an illustration of microbial size that compared different microbes to common features of a baseball park. Such comparisons can help you put into perspective how small microbes are compared to, say, a human cell using objects whose size is more familiar to you. That’s what this activity is all about. You’ll compare the sizes of different microbes to the size of a very familiar item—a human hair.
Note: This activity will take about 1 hour.
You’ll Need:

Note: If you do this activity in a parking lot, choose a day when that lot is not being used. You should definitely have at least one friend with you if not a parent or other adult. At least one person should keep a lookout for approaching cars at all times. Just be careful!
What To Do:
1. Examine your single hair both with and without the magnifying glass. Note how thin it is if you hold it at one end and look down at the tip. Depending on how thick your hair is, you may just barely be able to see it without the magnifying glass. The average human hair is 0.1 millimeters wide, or one-tenth of one millimeter wide. That’s pretty tiny.

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2. In your open space, use your meter stick to measure out an area that is 10 meters long. Mark off this 10-meter area with your chalk, string or tape, whatever works best for your chosen space. This 10-meter area will represent the width of your hair, that tiny width that you were barely able to see without a magnifying glass.
3. Choose one of the microbes from the first column of the Microbe Reference Chart. Think about how its size might compare to the width of your hair. Using the model size listed in column 4 of the Chart and your meter stick to measure, draw a picture of this microbe (or mark off its length and width with string or tape) somewhere beside the 10-meter area you already marked off. Once again, hold up your hair and see how tiny its width is and compare the actual size of the hair with the actual size (column 2) of the microbe.

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4. Repeat step 3 with additional microbes listed in the Reference Chart. You can do as many as you like. Use different colored chalk, tape or string for each microbe so you can remember which markings refer to which microbe.
5. When you’re finished drawing as many microbes as you’d like, compare the sizes and shapes of the microbes you've drawn. You have just created a reference model for microbial size.
6. Clean up your remaining pieces of chalk and remove tape or string when you’re done.  
Questions

  1. Why do scientists need to use models? Why can’t they just look under a microscope to see what they need to see? Answer
  2. Which kind of microbe is the smallest, a virus, bacterium or protozoan? Which is the biggest? Answer
  3. According to the Reference Chart, an E. coli bacterium is 2 micrometers long. Assuming that it's 1.25 micrometers wide, could you determine how many E. colicould fit on the tip of one of your hairs? Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

 Fun With Fomites

Fomites? What are fomites? This is a term for any inanimate object that can carry disease-causing organisms. Your cutting board, kitchen sink, the change in your pocket and even that pen you keep putting in your mouth are all fomites.

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Very few things we encounter in our everyday activities are sterile, or microbe-free, including us. At birth, microbes immediately begin colonizing our bodies as they do most every object in the world. They float around until they come in contact with a surface that offers food and shelter. You are most likely to find microbes in and on dark, moist objects that frequently come into contact with food, dirt or vegetation. Bathroom surfaces, hairbrushes, refrigerators, kitchen sinks and cutting boards often have lots of microbes on them. But doorknobs and walls have fewer because they are nutrient-poor and dry.
Most of the microbes on our bodies and other surfaces are harmless, but some are pathogenic or disease-causing. For this reason, we want to control the number of microbes around us. The odds of becoming infected increase with the number of microbes on surrounding objects. But what can we do to affect the number of microbes on surfaces around us?
In this activity, you will test a chosen fomite for the presence of microbes and the effects of a disinfectant by growing colonies of bacteria in a medium on petri plates. A medium has food, vitamins and salts that help microbes grow. You usually don’t see bacterial colonies like those that form on petri plates on everyday surfaces. That’s because there is rarely such a perfect concentration of nutrients on fomites in nature.
Note: This is an activity that you will start on one day and finish on a different day.
You’ll Need:

What To Do:
1. If you have long hair, tie it back to keep it from dangling into the petri plates as you’re working. Wash your hands. Clean your work area by dabbing, not pouring, disinfectant solution onto a paper towel and swabbing your area. Set out your petri plates but DO NOT OPEN THE PLATES UNTIL YOU'RE TOLD.
2. Choose an object in the room (doorknob, picture frame, toy, kitchen counter, TV remote control, coin, etc.). Take one unopened petri plate and using your grease pencil or marker, divide the bottom of the plate into four equal sections. Write the object’s name across the top and label the sections 1 through 4. Open the box of cotton swabs and select one being careful not to touch the tip. Swab your chosen object with all sides of the swab tip by turning and twisting the swab as you move it across the object’s surface.

 

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3. Now open the lid of the plate and GENTLY make four streaks on the plate’s surface as shown in the illustration, starting in the section labeled "1" and continuing streaking in order of the sections, making your last streak in section 4. Use firm, but GENTLE pressure and do not retrace your previous streaks. Your streaks should make only very slight impressions in the agar—don’t gouge. Close the plate and seal it shut with two pieces of tape placed along the side—don’t cover over the top with tape or you won’t be able to see the inside of it well.

 

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4. Divide a second unopened petri plate into 4 sections numbered 1 through 4 and label it "Control." Clean half of the object you swabbed with a paper towel dampened with plain water—just wipe a couple of times; don’t scrub. Using a new cotton swab, swab the cleaned area for microbes. Open the lid of the second plate and GENTLY make 4 streaks on the plate’s surface, following the order of the numbered sections as you did previously. Close the plate and seal it.
5. Divide your third petri plate into 4 numbered sections and label it with the name of the disinfectant you’ve chosen (e.g. "Bleach"). Use your chosen disinfectant to clean the other half of the object you swabbed. Using another new cotton swab, swab the area for microbes. Repeat the process of streaking the plate. Close and seal the plate.
6. Soak the used cotton swabs in disinfectant and throw them away. Place your plates in an out of the way spot and let them incubate at room temperature for two days. Clean your work area with disinfectant solution. Wash your hands.
7. After two days have passed, look at your initial petri plate. Do not open it. Examine your other petri plates in turn without opening them. Create a table that compares the plates made before and after cleaning the object (see sample table below). Be sure to indicate whether microbes grew in each streak.
8. Note: An adult supervisor preferably should do this step. Very carefully open the petri plates in a sink and flood them with undiluted bleach or alcohol. Let stand for an hour and then rinse them out thoroughly, tie them in a plastic bag and throw them away. Be sure not to touch the plate surfaces when you open them and wash your hands thoroughly after handling the plates. Clean your work area with disinfectant solution.
Sample Table

 

Plate 1

Plate 2

Plate 3

Streak

1

2

3

4

1

2

3

4

1

2

3

4

Growth

X

X

X

X

X

X

 

 

X

 

 

 


Note: You can try variations of this activity to test different things. For example, you may want to test the sterilizing power of different types of soaps or cleansers. To do this, you would pick a large object, such as a kitchen counter, and divide it into 4 or more sections. Swab one section that you don’t clean. Wipe each of the other sections with a different cleanser and swab each, using a different petri plate for each section. Compare the plates after a few days.
Questions

  1. Which plate grew the most and biggest colonies? Why do you think that is? Answer
  2. Do you see a pattern in the size and amount of colonies in each plate? Answer
  3. How can we control microbial contamination? Answer
  4. If you tested more than one fomite, which one grew more microbes? Why is that?Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

 Yeast On The Rise

 

 

As you probably know from eating numerous meals, all breads are not the same. Tortillas and pitas are flat and dense, while loaves of sandwich bread and dinner rolls are puffy and lighter. In fact, if you look closely at a piece of

sandwich bread, you can see a honeycomb texture in it where bubbles formed and burst. Why these differences? Aren’t all breads made of the same basic ingredients? What made those bubbles?

 

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The differences are caused by a microbe called yeast, pictured here. Yeast is a kind of fungus. If you open up a package of baker’s yeast bought from the supermarket and sprinkle some out, you’ll see tiny brownish grains. These are clumps of dehydrated yeast cells (dehydrated means most of the water has been removed). Let them sit there for a while and watch them and you’ll soon get bored. They don’t exactly do much, do they? But put them in bread dough and after a while you can definitely see that they must be doing something. But what exactly are they doing?
You’ll find out in this activity in which you’ll make your own bread dough. Print out these pages and follow the directions to do this activity at home. When you're done, come back to this page to test your newfound knowledge by answering the questions at the end. (No fair peeking at the answers before you do the activity!)
Note: This activity can be done within one hour, though you could stretch it over a few hours if you wish, depending on how many different sweeteners you want to try.
You’ll Need:

What To Do:
1. Using the ruler, measure the point 3 centimeters from one end of each straw and mark that point with a line using the permanent marker.
2. Put ¼ cup of flour into each of your bowls. Mark the first bowl as the "Control." Mark the others as 1, 2, and 3. (Just imagine that the dough in the illustration below is in four separate bowls.)

 

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3. Measure 1 teaspoon of sugar and add it to the flour in the bowl marked 1. Put 2 teaspoons of sugar into bowl 2. Put 3 teaspoons of sugar into bowl 3.
4. Pour ¼ of a package of yeast (or ¼ teaspoon) into each of the four bowls. Using the spoon, stir together the ingredients in each bowl starting with the Control bowl.

 

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5. Fill a cup with warm water from your faucet. The water should be warm, not hot and steaming. Dust your hands with a little flour. Carefully add the water to the Control bowl about a teaspoonful at a time and begin to knead the mixture. Your dough should eventually feel kind of like Play-Doh—it should be damp, not wet.  It’ll be sticky at first, but should eventually reach a point where it’s just damp enough that it no longer really sticks to the bowl or your hands. If it’s too sticky still, add a little bit more flour. Form the dough into a ball.
6. Repeat step 5 with each of the remaining bowls, working as quickly as you can. (If you have friends or classmates or parents helping out, each person should take a bowl and everyone should do step 5 at the same time.)
7. Working quickly, push three straws into the Control dough until the dough inside the straw reaches the 3-centimeter mark. Lay these straws by the Control bowl. Repeat this step with each of the remaining bowls. Be sure to keep the straws beside the right bowls and don’t mix them up. (Again, if you’ve got more people working with you on this activity, each person should take a ball of dough and everyone should do this step all at the same time.)

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8. Now pinch the bottoms of each of your Control dough straws, pushing the dough up from the bottom enough to clip a clothespin to the end of each straw. Mark the new height of the dough on each straw. Stand the straws upright using the clothespins as bases. Do the same with the rest of the straws. Label the batches of straws as Control, 1, 2 and 3.

 

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9. Mark the time on your clock or watch or set your timer for 10 minutes. Wait 10 minutes. Then measure and mark the heights of the dough in each straw and record these heights and the time in your notebook. Repeat this step 10 minutes later. Repeat after another 10 minutes has passed.
10. During the 10-minute intervals while waiting for the dough in the straws to do its thing, discard your first batches of dough from each bowl and wash the bowls out. Dry them thoroughly. Be sure to keep an eye on the clock while you’re doing this so that you don’t miss the 10-minute deadline to check and measure your straws.
11. Repeat the dough making process only this time use a different kind of sweetener than sugar. Repeat the steps of filling and marking the straws. Label the new batch of straws and set them away from your first batch. Repeat the process of measuring the dough height in the straws at 10-minute intervals and recording the results in your notebook. Be sure to record the heights of this new batch of straws separately from the first batch.
12. Graph your results. First, calculate the average final height for each set of three straws in your first batch. Make a bar graph showing these average heights with the number of teaspoons of sugar (0, 1, 2, 3) on the horizontal axis and the height in centimeters on the vertical axis. Make a similar bar graph for your second batch of straws. See the sample graph on the right.

 

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13. Throw away all the straws when you’re done. You might want to save the clothespins for another project in the future. Discard the dough in the bowls and wash them out. Clean up any spilled flour, sugar or yeast.
Questions

  1. In the first batch of straws you made, which straws showed the greatest change in dough height? Why?  Answer
  2. Can you guess what effect the sugar had and why?  Answer
  3. Did the Control dough rise at all or not? Why or why not?  Answer
  4. Did your dough made using a different sweetener besides sugar show the same results?   Answer

This experiment is based on an activity developed by the National Association of Biology Teachers.

 Microbial Slime!

Run your tongue over your teeth. If it's been a while since you last brushed, you may feel a filmy or fuzzy coating on your teeth. What's there is similar to the slimy coating you might feel if you stuck your finger down into a sink drain or that you might see coating the sides and bottom of a swimming pool that hasn't been kept clean. These are all examples of biofilms.
Biofilms are communities of microbes. They form when bacterial cells able to make large amounts of sticky, slimy substances called polysaccharides (polly-sack-uh-rides) attach themselves to a surface. The slimy coating they make holds the cells to the surface they've settled on and captures other bacteria who live and grow off the waste products produced by the first bacteria. Layers keep being added, creating a complex community.
In this activity, you'll explore whether biofilms can form on all possible surfaces and which they grow best on. You'll also learn something about how we can prevent biofilm formation.
Print out these pages and follow the directions to do this activity at home. When you're done, come back to this page to test your newfound knowledge by answering the questions below. (No fair peeking at the answers before you do the activity!)
Note: This is a long-term activity that will stretch over a several days.
You’ll Need:

Note: Be careful handling sharp scissors.
What To Do:
1. Create an artificial pond: Fill your large bucket with tap water, place it on newspaper and let it sit for 24 hours. Pour 2 cups of dirt or mud into the bucket and stir in. Make sure the dirt is as free of chemicals as possible (e.g. don't use dirt from a garden treated with weed or insect killers). Or if you have a stream or pond nearby, you could just fill a bucket with water and dirt from there. Be very careful around bodies of water that are or may be deep. Fill your bucket near the edge and don't go into the water. Wash your hands when done.


2. Using the scissors, cut the top and bottom off your soda bottle about 5 cm from each end. Throw away the top and bottom.

The remaining part of the bottle looks like a cylinder. Cut through it from top to bottom to create a rectangular piece.

Flatten the piece and then cut into 5 equal strips.

Punch a hole into each end of each strip.

 

 

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3. Set one strip aside. Spread newspaper or paper towels on a table. Working over the newspaper, coat each of the other 4 strips, front and back, with a different coating. Use only one coating substance for each strip. Set them on the newspaper and let them dry (drying time will vary for each coating substance used).
4. Arrange your 5 strips in a row so that they are parallel. Thread a piece of string through the hole in one end of one strip and pull it through, leaving about about 7 cm hanging. Tie the strip to the string. Thread the long end of the string through one hole of the next strip and tie it off about 3 cm from the first strip.

 

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Continue to thread the strips onto the string, keeping them 3 cm apart. Using your second string, repeat this process on the other side of the the 5 strips. Tie whatever you're using as weights (washers, fishing weights, stones) to the 7 cm ends of the strings. Tie the other ends of your strings together. Your setup should look like the picture here.
5. Hang your setup from the stick or dowel and lay the stick across the top of your artificial pond so that the setup hangs down into the water. All strips should be submerged, but they shouldn't be resting on the bottom. Wash your hands. Leave the bucket and setup undisturbed for two weeks (check occasionally to make sure your top strips are still covered by water).
6. Working carefully around your setup so you don't jostle it badly, remove a few cups of water from your artificial pond and pour into your shallow pan or small bucket placed on newspaper. Carefully move your setup to this pan or bucket so that it doesn't dry out while you're working with it.

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7. Touching and lifting strips very carefully so you don't rub off the biofilms, examine the surface of your strips with the magnifying glass. You'll likely see green, brown, pink or reddish spots. Rate the amount of growth on each strip on a scale of 1 to 5 (1 being the least growth). Give the uncoated strip a 3 rating and rate the other strips compared to it. Create a bar graph with the different coatings labeled on the horizontal axis and the growth ratings on the vertical axis. Wash your hands after touching strips.
Questions

  1. Which coatings did the biofilms form best on? Which did they grow least well on?  Answer
  2. What do your results tell you about biofilm formation?  Answer
  3. Can you think of some problems biofilms might cause? Can you think of any useful things they might do?  Answer

If you want more details about biofilms and to see an animation showing how biofilms form, visit this Web site.
This experiment is based on an activity developed by the National Association of Biology Teachers.

Reference:

http://archives.microbeworld.org/resources/experiment/experiment_microbial_slime.aspx

 

 

 

 

 

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