Study Material on useful and harmful Microbes for Class 8 NCERT Science

5. Is a Bacterium that
sours milk and is used to make curd
from milk . Starter curd multiplies and
coverts the milk to curd .
It is also used for making Cheese.
Fungus Used in making
Bread , cake , Pastry.

6. Yeast is mixed with sugar for making the
bread, bun , cakes etc.
This breaks sugar to form alcohol and CO2 is
given off. -This process is called as
Fermentation
The bubbles of CO2 makes the cake dough
rise and Makes the cake fluffy and spongy.
Same process occurs in Idly and Dhokla
Batter

7.  Fermentation of Sugar withYeast produces
Alcohol which is used to make Beer andWine.
 Wine : Sugar is obtained from Grapes
 Beer : Sugar is obtained from Barley .
 Algin : Obtained from Algae to make Jellies
and Ice creams etc.

8.  Bacteria & Fungi are used to make Antibiotics
 Antibiotics are medicines which kill or stop
the growth the of disease causing Microbes.
 Examples are :
Penicillin - Penicillium ( Algae)
Streptomycin , Erythromycin ,Tetracycline
(from Bacteria and Algae )

9. Are dead and weakened microbes , they
produce antibodies to fight against diseases
like
Typhoid,Tuberculosis, Hepatitis , small pox,
chicken pox , measles , polio etc.
Vaccination is also called as Immunization.
Vitamin B capsules --- Bacteria &Yeast
Insulin -- Bacteria

10.  Rhizobium & Blue Green Algae –
Nitrogen Fixing
 Environment Cleaning :
 Bacteria , Fungi and Protozoa – Decomposition of
dead organism for their food
 Decomposition of Organic matter – Manure
 Decomposition of Sewage and Other waste water

11.  Help the animals to digest their food
 Tanning – In jute , leather Industries
 Bio Gas Production – Methane CH3

12. Harmful

14.  They cause diseases --- Germs
 Pathogens is the scientific name of Germs.
 Disease is caused when pathogens enter our
body .

15. Cuts &
Wounds

16.  Insects and Animals are the Carriers of
Pathogens
 House Fly : Food Poisoning
 Female Anopheles mosquito- Malaria
through the parasite of malaria
called Plasmodium
 Female Aedes mosquito - Dengu
through the dengue virus called Flavivirus

17. Food
Poisoning

18.  Anthrax: A dangerous disease that affects
human and cattle is caused by a bacterium
called Bacillus Anthracis.
 Foot and mouth disease in Cattle:
It is caused by a virus called Foot-and-mouth-
diseaseVirus (FMDV) or Picornavirus.

20. Microorganisms
can cause
diseases in plants
and reduce crop
yield.

22. By : Kalyani . S