Maharashtra Board Class 9 Science Chapter 8 Useful and Harmful Microbes Solution

Maharashtra Board Class 9 Science Solution Chapter 8 – Useful and Harmful Microbes

Balbharati Maharashtra Board Class 9 Science Solution Chapter 8: Useful and Harmful Microbes. Marathi or English Medium Students of Class 9 get here Useful and Harmful Microbes full Exercise Solution.


Maharashtra Class 9

Science Solution


Useful and Harmful Microbes

1.) Complete the statement using the proper option from those given below.

(Mycotoxins, budding, Rhizobium)


a) Yeast reproduces asexually by the budding

b) Toxins of fungal origin are called mycotoxins.

c) Leguminous plants can produce more proteins due to Rhizobium.

2.) Write the names of the microbes found in the following food materials.


Yoghurt- Lactobacillus

Bread – Saccharomyces

Root nodules of Leguminous plants – Rhizobium

Idli – lactobacillus

Dosa – Lactobacillus

Spoiled potato curry – Clostridium

3.) Identify the odd word out and say why it is the odd one.


a) Pneumonia, diphtheria, chicken pox, cholera.

Odd word: Chicken pox

Because chicken pox is a viral disease while all the other are bacterial disease.

b) Lactobacilli, rhizobia, yeast, clostridia

Odd word: rhizobia

Because rhizobia is the bacteria found in plants while all the other are the bacteria related to human food products.

c) Root rot, rust, rubella, mozaic

Odd word: rubella

Because rubella is the human disease while all the other are the diseases found in plants.

4.) Give scientific reasons.

a) Foam accumulates on the surface of ‘dal’ kept for long time in summer.


Denatured proteins are released from the dal when it is in contact with water for long time in summer.

When these denatured proteins are mixed with the water then it forms the foam. As these process requires more temperature and hence it happens quickly in summer.

b) Why are naphthalene balls kept with cloths to be put away.


Naphthalene balls are kept with cloths because when they kept in cloths sublime slowly and after sublimation there will be no residue left. And hence their work is to avoid the insects coming in contact with cloths which damage the cloths.

Hence, naphthalene balls are kept within the cloths or kept with cloths.

5.) Write down the modes of infection and the preventive measures against the fungal diseases.


  • Fungal infections are due to the fungi found in soil, water, plants, animals, air and also on the people.
  • Fungal infections are occurred due to the contact of healthy person with the spores of the fungi.
  • Also if the healthy person is arrived in contact with affected soil, water or air then also it get infected.
  • When there is fungal infection to skin then it will be infected from person to person also.
  • Fungal infections are not like that serious but when it becomes AIDS it will be very dangerous.

The fungal infections are prevented by taking following measures:

  • We have to maintain our hygiene clean, clear and proper.
  • To prevent fungal infections we have to avoid the use of personal products like hair brush and other materials.
  • We have to avoid the contact of infected person directly.
  • We have to wash and discard the infected all the materials and objects.
  • We have to avoid wearing the tight cloths like jeans and also avoid to wear shoes.

 6.) Match the pairs.


1) Rhizobium: Nitrogen fixation

2) Clostridium: Food poisoning

3) Penicillium: Production of antibiotics

4) Yeast: Bakery products

7.) Answer the following questions.

a) Which vaccines are given to infants? Why?


  • The various kinds of vaccines are given to the infants between 0-12 months. Some of them are BCG vaccination, Hepatitis B, Oral Polio vaccine, Rota V etc.
  • Vaccine are mostly given to young children’s as their immune system is not fully developed and their stomachs produces less acid which multiplies the bacteria and viruses ingested.

b) How is a vaccine produced?


  • Vaccine are nothing but the some dead or weakened organisms which helps the body to fight against the various kinds of diseases.
  • Hence, to protect our body from the diseases caused by the microorganisms some dead or weakened organisms are introduced through vaccine in our body due to which antibodies are produced in our body.
  • And these antibodies produced are long lasting and remain in our body to protect from diseases.
  • Our body reacts to the microorganisms by producing antibodies which kills the microorganisms causing disease to us.

c) How do antibiotics cause disease?


  • Microorganisms are surviving due to their certain biochemical pathway. Such as in respiration and enzyme synthesis.
  • Antibiotics binds with their precursor needed to follow these pathways and when the essential life processes are absent it blocks them and microorganisms get killed.

For example:

  • Penicillin by blocking the cell wall formation in the bacteria kills the bacterium.
  • As the diseases causing microorganisms got dead then there will be no more microorganisms are produced and the person become recovering from the disease.

d) Are the antibiotics given to human and animals the same? Why?


The diseases causing to animals and humans are different so the microorganisms which cause the disease will also be different in animals and humans.

As the pathogen of diseases are different in animals and humans hence different antibiotics are also required.

When the pathogen causing the disease in animals and humans is the same then there will be same antibiotics are administered to the animals and humans also.

e) Why it is necessary to safely store pathogens of disease against which vaccines are to be protected?


  • Vaccines are the dead or weakened organisms which increase the immunity against the disease. As these are the dead and weakened organisms they may lost their diseases spreading ability and hence no harm will be caused to our body.
  • If we have not stored these organisms properly and if they are in their infective stage till then they can spread the disease through air also.

 8.) Answer the following questions in brief.

a) What are broad spectrum antibiotics?


The broad spectrum antibiotics are the antibiotics existing over the wide range which kills the gram positive and gram negative bacteria in wide range.

Ofloxacin, vancomycin, chloramphenicol, ampicillin etc are the broad spectrum antibiotics which exists over wide range.

b) What is fermentation?


The process in which complex organic compounds are decomposed into simpler one in the presence of enzyme is called as fermentation.

Curd is formed from the milk by the process of fermentation only.

The lactobacillus converts the lactose from milk into the lactic acid which reduces the pH of the milk and thereby milk proteins get separated and yoghurt of the milk is formed. This is real life example of fermentation.

c) Define antibiotics?


Antibiotics are the organic compounds which are also produced by the microorganisms which inhibits the growth or kills the other disease causing microorganisms.

Updated: August 28, 2021 — 3:47 pm

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