Theory:

Microorganisms play a significant role in our lives. There are many friendly microbes that help human beings in a variety of ways.
  • They are used in cleaning up the environment: for example, the organic wastes (vegetable peels, faeces, remains of animals, plants, etc.) are broken down by microorganisms and convert them into useful substances.
     
  • Bacteria like E.coli present in the human duct (alimentary canal) assist in the digestion of food. They also help in making, vitamins especially vitamin B. This is a kind of a symbiotic relationship which is mutually beneficial to both the bacteria and the host.
     
  • Bacteria are also used in increasing the soil fertility for agricultural purposes and also in the preparation of medicines.
     
  • Yeast is a bacteria used in the baking industries. 
 
Let us see how Yeast is being used in baking of bread through an activity.
 
Activity (try this at home):
  
Take half kilogram of maida, add sugar and mix with warm water. Add a small amount of yeast powder and knead to a soft dough. You can find the dough rising after 2 to 3 hours.
 
maida.PNG
 
How did that happen?
 
The Yeast mixed in the dough reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume. For this purpose, in bakeries, Yeast is used extensively.
 
We will discuss some of the disease-causing microorganisms in detail in the next material.