Essay On Microorganisms Friend And Foe Game

Title – Bacteria: Friend or Foe
By – Katie Kaufman
Primary Subject – Science
Secondary Subjects – Health / Physical Education
Grade Level – 4-5

Teacher Materials:

  1. Pictures of bacteria
  2. sink, soap, paper towels, waste basket
  3. hand washing diagram
  4. hand washing checklist ( 1 per student )
  5. pen/pencil

Student Materials:

  • Pencil
  • materials for experiment
  • hand washing diagram
  • sink, soap, paper towels, waste basket
  • evaluation sheet ( quiz )


  1. Given a pencil and paper, the student will be able to write two/three sentences describing what bacteria are in there own words. For their definition/description to be correct, they must say that bacteria are single celled organisms.
  2. From memory, the student will be able to list three ways that bacteria can be helpful.
  3. From memory, the student will be able to list two ways that bacteria can be harmful.
  4. Given soap, warm water and paper towels, the student will be able to properly demonstrate how to wash hands as learned in the lesson. Student should not miss any steps.


    Play a guessing game with students. You will describe something and they have to guess what you are describing. Don’t give the whole description at once, but as you describe, let students guess.


    1. Something that is alive.
    2. There are approximately five million trillion trillion of these on the earth.
    3. These things multiply very rapidly. They can double as quickly as ten minutes.
    4. Can live in live in extreme temperatures. Some have been found to live in under water volcano vents where it gets as hot as 700ºF and others live at the South Pole in temperatures as cold as – 120 ºF.
    5. These live almost everywhere. They cover everything, including your skin. They live in water, dirt, food, and in the air. They live inside you: in your mouth, stomach, and lungs.
    6. Some live in radioactive ( nuclear ) waste.
    7. Is so small we can only see it with a microscope.

      Answer : Bacteria


    “Today we are going to learn about bacteria.”

Sequence of Activities


      “Bacteria are living things that have only one cell. There are many different species of bacteria. Here are some pictures of bacteria magnified many, many times.” (

Show students pictures of magnified bacteria. Point out that bacteria are different shapes.

      “Do you think that bacteria are good or bad?” (

Let students answer

      “Actually, that was a trick question. Some species of bacteria are harmful and some are good.”

Discuss ways bacteria can be harmful and the solution/prevention of these problems.

      • Food poisoning : Food contains bacteria. If food is not stored at the proper temperature then the bacteria multiplies very rapidly. If this food is eaten it can cause nausea, vomiting, diarrhea, or in serious cases, death. Food poisoning can also be caused by eating food that is not cooked properly, like chicken or eggs. When food is cooked, harmful bacteria is killed ( bacteria is not the only cause of food poisoning ). E. Coli, Salmonella are more well known bacteria in food.

        Cook food thoroughly, especially meats. Refrigerate foods.

      • Bacterial Infections : includes strep throat, ear infections, pneumonia, and bronchitis. These are different from viruses. If treated properly, they are not life threatening, but if not treated can spread to other organs in the body.


      • Acne : caused in part by infection of bacteria in pores.

        do not touch face and spread bacteria to face; wash face

      • Cavities : caused by bacteria that eat sugar and convert it into acid plaque eats at tooth enamel.

        brushing teeth and flossing

      • Body Odor : when we sweat, bacteria begins to multiply rapidly n the warm, moist skin. The bacteria quickly multiply, then dies, releasing an odor as they decompose or rot.

        washing daily and wearing deodorant.

Discuss ways that bacteria are helpful.

      • Bacteria in the digestive systems of people and animals help break down food so that nutrients can be used and the waste disposed off. Good bacteria can fight of bad bacteria in the digestive system.
      • Bacteria help garbage and sewage to decompose. If there were not bacteria, there would be huge piles of garbage?
      • Dead Bacteria are used to produce antibiotics, and vaccines which help our bodies fight of bad or harmful bacteria.
      • Some bacteria produce oxygen.


    “The amount of good bacteria in the world far out numbers the amount of bad bacteria. Bacteria are necessary for human life. We just need to be careful not to spread bad bacteria. One simple way to prevent the spread of bacteria is hand washing.”

Experiment-Rub-A-Scrub: ( see handout below)

Hand Washing Activity:

      Give students hand-washing diagram. Verbally go over each step with them. Take students to a sink and demonstrate hand washing with the following steps (

verbalize steps as you demonstrate

        1. Wet your hands with warm water. Leave the water running.



        3. Scrub hands well for about 20 seconds. Make sure to scrub under fingernails where bacteria like to hide and multiply!


        4. Rinse well. Make sure to rinse all soap and dirt down the drain.



      6. Use the paper towel to turn of water, so hands do not become re-contaminated. Also, use the paper towel to open the door if it has a handle of knob. Throw paper towel in a wastebasket.

Evaluation of Students:

    Have students demonstrate hand washing according to the steps taught above. Use a checklist to grade each student. Student should not miss any steps.


      Review the material covered in lecture with question and answers.
      Q: “How many cells are in one bacterium?”



      Q: “Where are bacteria located?”


They cover almost everything; they are inside of your mouth and digestive system, in air, water, dirt

      Q: “How big are bacteria?”


They are so small that we can only see them with a microscope

      Q: “What is one way bacteria are harmful?”


Body odor, infections, food poisoning, cavities, etc

      Q: “What are some ways that bacteria are helpful?”


Help waste to decompose, make oxygen, help food digest, used to make medicines

      Q: “Are there more helpful or more harmful bacteria?”


more helpful

Evaluation of Students:

      Students take a quiz to see what they learned about bacteria. (

See below

Sources of Information:

  1. Wikipedia, the online encyclopedia; articles: Microorganisms, Bacteria 
  3. The weather notebook:
  4. What are Germs? 
  5. Best of Mailbox Science Grades 1-3; © 2006, The Education Center, Greensboro, NC




Microorganisms are the living organisms that are too small and invisible to the naked eye. Microorganisms are seen with the help of an instrument called as microscope. Microscopes can be of different types based on their complexity.

Microorganisms are omnipresent. Microorganisms are found everywhere, in the air, water, soil, in and on living organisms. Microorganisms can survive extreme conditions like hot springs to polar regions. They can survive too acidic and too alkaline environment. Under unfavourable conditions of temperature and water, they form hard and tough coverings called as cysts. As the favourable conditions prevail, they break open their cysts and continue their normal life cycles. 

Classification of microorganisms
1. Based on the characteristics, microorganisms can be classified into four groups – Bacteria, Fungi, Algae and Protozoa.
2. Based on the number of cells present, microorganisms can be unicellular or multicellular. Organisms which are made up of a single cell are unicellular while the organisms made up of many cells are multicellular forms. Most of the protozoans are unicellular in nature while most fungi and some algae are multicellular organisms.

3. Based on the significance, microorganisms can be useful or harmful to us.

Useful microorganisms
Microorganisms are extensively used in various fields and are of great economic importance.


Uses of microorganisms

a. Microorganisms are used in baking industry.
b. Microorganisms are used in the preparation of curd.
c. Microorganisms are used in commercial preparation of pickles, and many dairy products.
d. Microorganisms are used in industrial production of alcohol and wine. Yeast converts the natural sugars present in grains into alcohol. Wine is produced by the process of fermentation.The process of converting sugar into alcohol is called fermentation.
       •  Fermentation: Louis Pasteur discovered the process of fermentation. Fermentation is a slow biochemical process by which sugar molecules are broken down in the absence of air to produce alcohol and carbon dioxide. The process of fermentation is brought about by organisms like yeast which respire under anaerobic conditions.
e) Microorganisms like bacteria act as decomposers to clean up organic waste by decomposing them into usable substances.
       •  Decomposition: It is the process by which some organisms can convert dead and decaying matter into organic matter of the soil. These organisms which bring about decomposition are termed to be decomposers. Decomposers form an important part of the ecosystem.
f) Microorganisms are used to prepare medicines. These medicines are used in treatment of diseases caused by various microorganisms.
       •  Antibiotics: These are the substances produced by certain microorganisms and are used as medicines to kill pathogens. Antibiotics are used only against certain microorganisms. They are not effective against viruses.
g) Microorganisms are used in preparation of vaccines.
       •  Vaccines:  A vaccine is a collection of antigens of weak strains of particular disease causing microorganisms. When this is injected into the blood stream, it stimulates immune system to produce antibodies. These antibodies fight against weak antigens and some of them are stored in the blood to prevent the attack of that particular disease in future. This is the process by which vaccines develop immunity for a particular disease in our body.

Economic importance of bacteria
       •  Bacteria like lactobacilli are used in the preparation of curd.
       •  Bacteria are also used to prepare pickles and many dairy products.
       •  Bacteria are used in industrial production of alcohol and wine by the process of fermentation.
       •  Bacteria are useful in laboratories to test the effects of medicines.
       •  Bacteria act as decomposers to clean up the environment by performing the process of decomposition. Bacteria performing the process of decomposition are called as saprobes.
       •  Bacteria present in the soil aid in increasing soil fertility.
       •  Bacteria present in the soil fix the nitrogen to plants.
       •  Bacteria help in the tanning process of leather industries.
       •  Bacteria can also help in the digestion of sewage.

Economic importance of fungi
       •  Fungi are used in industries in the production of bakery products. Yeast is a microorganism which multiplies rapidly in dough and produces carbon dioxide. This dough, when baked, yields porous and spongy cakes. Yeasts are used in baking industry to provide puffiness to bread, cake and other bakery products.
       •  Fungi can be used as food in the form of Mushrooms and Morels.
       •  Fungi can be used in the production of antibiotics.
       •  Fungi are used in the production of wine by the process of fermentation.
       •  Fungi can be used in the commercial production of organic substances like citric acid, fumaric acid, lactic acid, oxalic acid etc.
       •  Fungi are used in agriculture to enhance the fertility of the soil.

Economic importance of algae
       •  Algae are photosynthetic microorganisms that can synthesise their own food which can be consumed by us. Algae are used as food as they are rich in carbohydrates, vitamins and few other inorganic substances. Spirogyra is the chief source of food. Some algae are found to be rich in protein content when compared to egg.
       •  Algae release lot of oxygen into water as a by-product of photosynthesis. This is the source of dissolved oxygen for aquatic organisms.
       •  Agar –Agar is used in preparation of ice-cream and jellies. e.g. Gelidium
       •  Algae are chewed instead of tobacco. e.g. Rhodomenia
       •  Algae are used extensively in industries to prepare some products like sugar, soap, cement, rubber blotting paper etc.
       •  Algae are used in agriculture to increase soil fertility e.g. Nostoc, Anabena.
       •  Algae are used to prepare algin used to prepare rollers for typewriters.
       •  Algae are used in the manufacture of paper and fabric paints.
       •  Some algae are used in the preparation of medicines.

Economic importance of protozoa
       •  Protozoans feed on fungi and bacteria which are harmful to human beings. Protozoans also help in decomposition of organic substances.
       •  Protozoans exist as symbionts providing habitat for other living organisms.
       •  Protozoans provide an important link in aquatic food chains.


Leave a Reply

Your email address will not be published. Required fields are marked *