Importance of Microbes MCQ Quiz - Objective Question with Answer for Importance of Microbes - Download Free PDF

The correct answer is A and C only

Explanation:

• Household products such as bread, curd, alcoholic beverages, and other fermented items are often prepared using specific microbes. These microbes play a vital role in enhancing the quality, flavor, and nutritional value of these products.
• Some microbes are industrially used for other purposes, such as the production of antibiotics or enzymes, but they are not involved in the preparation of common household products.
  • A) Aspergillus niger: This fungus is commonly used for the industrial production of citric acid and enzymes but is not involved in the preparation of household products.
  • B) Lactobacillus: This bacterium is involved in the preparation of household products like curd and yogurt. It helps in the fermentation of milk, converting lactose into lactic acid.
  • C) Trichoderma polysporum: This fungus is used industrially for the production of cyclosporin, an immunosuppressive drug. It is not involved in the preparation of household products.
  • D) Saccharomyces cerevisiae: Commonly known as baker's yeast, this microbe is widely used in the preparation of bread and alcoholic beverages like beer and wine. It plays a crucial role in fermentation, producing carbon dioxide and ethanol.
  • E) Propionibacterium shermanii: The large holes in ‘Swiss cheese’ are due to the production of a large amount of CO₂ by a bacterium named Propionibacterium sharmanii.

The correct answer is Heterotrophic microbes

Concept:

• Wastewater treatment primarily involves the removal of organic and inorganic contaminants to produce environmentally safe effluent and to recycle water back into the ecosystem.
• The treatment process often relies on biological methods, where various microorganisms degrade organic matter present in the wastewater.
• Heterotrophic microbes play a crucial role in breaking down organic pollutants through aerobic and anaerobic processes.

Explanation:

• Heterotrophic microbes:
  • These microbes consume organic compounds as their source of energy and carbon.
  • During wastewater treatment, they digest and decompose organic pollutants, thereby reducing the biochemical oxygen demand (BOD) and improving the quality of the water.
  • Common heterotrophic microbes used in wastewater treatment include bacteria such as Pseudomonas and fungi.
• Photosynthetic blue-green algae:
  • These algae, also known as cyanobacteria, perform photosynthesis and can aid in nutrient removal, but they are not the primary agents for degrading organic matter during wastewater treatment.
• Nitrogen fixing bacteria:
  • These bacteria convert atmospheric nitrogen into ammonia, aiding in soil fertility and agriculture but are not primarily involved in wastewater treatment.
• Chemosynthetic bacteria:
  • These bacteria obtain energy by oxidizing inorganic substances, such as hydrogen sulfide or ammonia, and play a key role in specific biochemical cycles but are not the main agents for organic pollutant degradation in wastewater treatment.

The correct answer is A - Settling, B - large aeration

Explanation:

The sewage water generated everyday in cities and towns from the household, factories etc ,contains a large amounts of organic matter and microbes, therefore it is treated in the Sewage treatment plants (STPs) before releasing it into waterbodies. 

This treatment is carried out in two stages-

• Primary treatment
• Secondary treatment

Primary treatment of the sewage involves the physical removal of the larger and smaller particles through filtration and sedimentation and then the effluent is then passed on to the large aeration tanks for the secondary treatment.

• The effluent from the primary settling tank is taken for secondary treatment.
• The primary effluent is passed into large aeration tanks (Figure 8.6) where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh like structures).

The correct answer is Cyanobacteria

Explanation:

Cyanobacteria:

• Cyanobacteria, also known as blue-green algae, are a phylum of bacteria that obtain their energy through photosynthesis.
• They have specialized cells called heterocysts that are capable of fixing atmospheric nitrogen (N₂) into ammonia (NH₃), which can be utilized by plants.
• This nitrogen-fixing capacity is crucial for enriching soil fertility and supporting plant growth in various ecosystems.

Archaebacteria:

• Archaebacteria, or Archaea, are a group of single-celled microorganisms that are similar to bacteria but have distinct genetic and biochemical properties.
• They are known for living in extreme environments like hot springs, salt lakes, and deep-sea hydrothermal vents.
• While some Archaea can fix nitrogen, they do not possess heterocysts and are not classified as cyanobacteria.

Mycoplasma:

• Mycoplasma are a genus of bacteria that lack a cell wall around their cell membrane, making them unique among prokaryotes.
• They are known for causing various diseases in plants and animals, including humans.
• Mycoplasma are not capable of photosynthesis or nitrogen fixation.

The correct answer is CH4 + CO2 + H₂

Explanation:

• Biogas is a mixture of gases that is produced by the microbial breakdown of cellulosic materials in anaerobic conditions.
• The biogas majorly consists of Methane (CH4), but also contains Carbon dioxide (CO2) and Hydrogen sulfide (H2S).
• The bacteria which grow anaerobically to produce methane as a metabolic byproduct are known as Methanogens.
• Methanobacterium is the most common example of Methanogen.
• These bacteria are found in the anaerobic sludge during the secondary treatment of sewage and they produce biogas.
• These bacteria are also found in the rumen of the cattle.

• The biogas is produced in the biogas plant which consists of a tank made of concrete and is 10-15 feet deep.
• In this tank, the slurry of dung and other bio-wastes are collected and a floating cover is placed over it.
• This tank has an outlet, through which the biogas exits the tank to be supplied to the nearby households through a pipeline.
• This biogas may be used as a fuel for cooking and lighting.
• The spent slurry is removed through another outlet of the tank to be used as a manure or fertilizer in the fields.
• This technology of biogas production from cow dung was developed in India largely due to the efforts of -
  • Indian Agricultural Research Institute (IARI)
  • Khadi & Village Industries Commission (KVIC)

Concept:

• Methanogens are the bacteria which are responsible for the production of biogas.
• Biogas is a mixture of gases that is produced by the break down of organic matter like food scraps and animal waste, due to microbial activity.
• The microbial breakdown of cellulosic materials takes place in anaerobic conditions and the biogas is produced as a by-product.
• This biogas gas is used as a fuel for cooking and lighting.
• The biogas is produced during the secondary sewage treatment process.
• The biogas produced by using the cattle dung is also known as gobar gas.
• The biogas is produced in the biogas plant which consists of a tank made of concrete and 10-15  feet deep.
• In this tank the slurry of dung and also the bio wastes collected are fed into.
• A floating cover is also placed over it.
• This tank has an outlet for the gobar gas being produced which connects to the nearby households through a pipeline.
• The biogas or gobar gas is now used for different domestic purposes.

Explanation:

• The bacteria which grow anaerobically produce methane as a metabolic byproduct are known as Methanogens.
• These methanogens grow on the cellulosic material.
• Methanogens mostly produce Methane (CH4) and along with that some amount of carbon dioxide (CO2) and Hydrogen sulphide (H2S).
• This mixture of gases produced by the methanogens is known as Biogas.
• Therefore, Oxygen is not produced by the methanogens.

So the correct answer is Option (1).

Key Points

• Enzymes are catalysts that help in increasing the rate of a chemical reaction.
• Enzymes are essential for various metabolic activities in our body.
• However, enzymes are also important in the industries, where they are used for various processes.
• Example - 
  • Amylases - are used in processed food industry like baking.
  • Pectinases & Proteases - are used to clarify bottled juices.
  • Lipases - are used in detergent formulations as they help in removing oily stains from our laundry.
  • Streptokinase - is an enzyme that is used as a 'clot-buster' medicine for patients who have had heart attacks.
• These enzymes are obtained from various microbes for industrial production. 

Hence, the correct answer is option 3.

Additional InformationOther Industrial Microbial Products - 

• Penicillin - It is an antibiotic that is obtained from the fungus Penicillium notatum.
• Cyclosporin A - It is an immunosuppressive agent that is obtained from the fungus Trichoderma polysporum.
• Statins - are blood cholesterol-lowering agents that are obtained from a type of yeast called Monascus pupureus.

• Biocontrol refers to the use of biological methods for controlling plant diseases and pests.
• Biocontrol agents are the organisms that are used for this purpose.
• It is one of the novel methods that is followed in organic farming.

Important Points

Statement I - CORRECT

• Some common biocontrol agents include:
  • Ladybird - against aphids
  • Dragonflies - against mosquitoes
  • Trichoderma - is a free-living fungal species that is commonly found in root ecosystems and are effective against several plant pathogens.

Statement II - CORRECT

• Biological control of plant diseases and pests depends on natural predation and not chemicals.
• It creates a system where pests are not eradicated but maintained balanced in the ecosystem.
• It is believed that greater biodiversity brings greater sustainability.

Therefore, both statements I and II are correct.

Hence, the correct answer is option 1.

Concept:

• Microbes play an important role for the production of industrial products.
• They are used for fermented beverages, antibiotics, bioactive molecules as well as food products like cheese.
• Microbes may include bacteria as well as fungi.
• Various microbes are used for the production of different bioactive molecules in the industry, as given in the columns.

Explanation:

Corrected Table - 

Therefore, the correct match of the columns is: A - iv, B - iii, C - ii, D - i.

Hence, the correct answer is option (3).

Additional InformationOther microbes and their usage - 

• Penicillium notatum - Antibiotic Penicillin
• Trichoderma polysporum - Immunosuppressive agent Cyclosporin A.
• Monascus pupureus - Blood-cholesterol lowering agent Statins.
• Methanobacterium - Biogas production.
• Propionibacterium shermanii - Swiss cheese production.

Concept:

• Microbes play an important role for the production of industrial products.
• They are used for fermented beverages, antibiotics, bioactive molecules as well as food products like cheese.
• Microbes may include bacteria as well as fungi.

Important Points

• Streptokinase - 
  • Streptokinase is known as a 'clot buster'.
  • Streptococcus bacteria are used industrially to produce Streptokinase.
  • It is used to remove unwanted blood clots in the blood vessels.
  • It is particularly useful in patients who have undergone myocardial infarction leading to heart attack.
  • The bacteria Streptococcus may also be genetically modified to produce the desired bioactive molecule.
• Cyclosporin A - 
  • ​Cyclosporin A is produced from the fungus Trichoderma polysporum.
  • Cyclosporin A is used as an immunosuppressive agent in organ transplant patients.
• Statins - 
  • Statins are blood cholesterol-lowering agents.
  • It can induce competitive inhibition of the enzyme responsible for synthesis of cholesterol.
  • It can be industrially obtained from a type of yeast called Monascus purpureus.
• Swiss Cheese -
  • ​Swiss cheese are formed by the bacterium Propionibacterium shermanii.
  • The large holes seen in Swiss cheese are its characteristic feature.
  • They are formed due to CO₂ production by the bacterial respiration.

Corrected Table:

Hence, the correct answer is option 2.

Concept:

• Microorganisms are mainly known to cause diseases, but they also contribute in human welfare.
• In our everyday lives we use different microbes and their product derivatives.
• Microbes play a very important role like-
  • In the production of foods like curd, idli, dosa, cheese etc.
  • Production of fermented beverages like wine, beer, whisky, beer, brandy etc.
  • Microbes are used in production of antibiotics.
  • They play a major role in the sewage treatment.
  • Thy produce different bioactive substances like lipases, pectinases, cyclosporin etc. which are used for industrial and medicinal purposes.

Important Points

Option 1- Lady bird

• Beetles like Ladybird and Dragonflies are used for getting rid of the aphids and mosquitoes.
• Thus, they are known as biocontrol agents.

Option 2- Mycorrhiza

• The symbiotic association between the plant roots and fungi is known as Mycorrhiza.
• It helps the plants in enhancing the capacity of uptake of nutrients and water from the soil.
• Members of the genus Glomus form mycorrhizal association with plants.

Option 3- Biological control

• The fungus Trichoderma is used for biological control of plant diseases and acts against various pathogens.
• Trichoderma species are the free living fungi which are commonly found in the root ecosystem.

Option 4- Biogas

• Biogas is a mixture of gases that is produced by the microbial activity causing breakdown of organic matter like food scraps and animal waste.
• The microbial breakdown of cellulosic materials takes place in anaerobic conditions.
• The biogas majorly consists of Methane (CH₄), CO₂ and H₂S.
• The bacteria which grow anaerobically to produce methane as a metabolic byproduct are known as Methanogens.
• Methanobacterium is the most common example of Methanogen.

Corrected table:

Hence, the correct answer is option 2: A - iii, B - iv, C - ii, D - i.

• Sewage is wastewater that is discharged from households, residential areas, hospitals, businesses, and other places.
• Wastewater or sewage contains large amounts of organic matter and microbes.
• It is polluted and contaminated, pollutants are removed from the sewage before it enters any water body or is reused.
• Sewage is treated in sewage treatment plants (STPs)
  to make it less polluting.
• Treatment of waste water is done by the heterotrophic microbes naturally present in the sewage. 
• This treatment is carried out in two stages - Primary treatment and Secondary treatment.
• Primary treatment basically involves the physical removal of large and small particles from the sewage through filtration and sedimentation.
• All solids that settle form the primary sludge, and the supernatant forms the effluent.
• The effluent from the primary settling tank is taken for secondary treatment.

Important Points

• Secondary treatment of sewage involves living organisms such as aerobic or anaerobic microbes to digest the organic waste, hence this process is referred to as biological treatment.
• The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it.
• This allows vigorous growth of useful aerobic microbes into flocs. Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
• This results in a significant decrease in BOD (Biological Oxygen Demand) and the sewage water is treated till the BOD is reduced.
• BOD refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
• BOD is a measure of the organic matter present in the water.
• The greater the BOD of wastewater, the more polluting potential.
• Once the BOD of sewage or wastewater is reduced significantly, the effluent is then passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment.

Hence the correct option is (2) to reduce the BOD.

Concept:

• Microbes and their products are used in biotechnological industries for human welfare.
• Microbes like bacteria, fungi, viruses, etc., and their products have been used for their beneficial activities to man.
• Medicine, food, health, agriculture, etc. are some of the industries where microbes are used.
• Microbes are also used for the production of amino acids on large scale.
• Amino acids can be produced using microorganisms by utilizing carbon sources such as glucose, fructose, glycerol, etc.
• Molasses and starch hydrolysate can also be used for the production of amino acids by microorganisms.
• Microbial enzymes can also be used for the production of amino acids.
• Amino acids such as glutamic acid, alanine, leucine, phenylalanine, etc. are some of the amino acids that can be produced with the help of microorganisms.

Important Points

• Option 1: Corynebacterium - CORRECT
  • ​Corynebacterium and  Brevibacterium are used for the production of glutamic acid.
  • The sources used by these microbes for the production of glutamic acid are sugar and beet molasses and ammonia salt.
  • In the food industry, glutamic acid is used in the production of monosodium glutamate (Ajinomoto).
• Option 2: Arthrobacter - INCORRECT
  • Arthrobacter is a bacteria found in soil.
  • They are also found in ready-to-eat vegetables, raw milk, eggs, etc.
  • Arthrobacter plays an important role in biodegrading pollutants and agrochemicals. This is due to its property of degrading polymeric compounds.
• Option 3: Thermoanaerobacter - INCORRECT
  • Thermoanaerobacter is a genus of bacteria that are known to grow in the absence of air at elevated temperatures i.e. they are thermophiles.
  • They are known to reduce organic acids to their corresponding alcohols.
• Option 4: Enterobacter - INCORRECT
  • ​Enterobacter is a genus of rod-shaped bacteria that are facultative anaerobes.
  • Enterobacter aerogenes in particular is used for the production of 2,3-Butanediol.
  • This compound is used in the production of printing inks, perfumes, fuel additives, pharmaceuticals, etc.

So the correct answer is option 1 (Corynebacterium).

Concept:

• Microbes and their products have long been used in biotechnological industries for human welfare.
• Microbes like bacteria, fungi, viruses, etc., and their products have been used for their beneficial activities to man.
• Medicine, food, health, agriculture, etc. are some of the industries where microbes are used.
• Probiotic foods are one such product containing bacteria that has proven to be beneficial to humans.

Probiotics:

• Probiotics are active bacteria or yeast that help in maintaining the good health of the digestive system.
• Mode of action:
  • Help restore the population of good bacteria in the body that were lost or had become inactive due to the consumption of antibiotics.
  • The active bacteria present in the probiotics form colonies of useful microbes in the alimentary canal and control the population of other microbes.
  • It decreases the population of harmful microbes inside the body such as Clostridium.
  • Similarly, it increases the population of good bacteria thus helping in digestion.
  • Apart from this it also helps improve resistance and lower the ill effects of harmful substances that are produced during metabolic activities.
• Types of bacteria:
  • Lactobacillus - Most common probiotic. Helps with diarrhea and digestion of lactose.
  • Bifidobacterium - Helps ease the symptoms of irritable bowel syndrome (IBS).
  • Saccharomyces boulardii - It is a species of yeast that works as a probiotic. Helps fight diarrhea and aids in digestion.
• Probiotic foods:
  • Yogurt
  • Kefir
  • Sauerkraut
  • Dark chocolate
  • Miso soups

Additional Information

• ​Bacillus coagulans - is a species of bacteria that is a probiotic that aids in stomach-related ailments.
• Bacteria belonging to the genera Staphylococcus are known to be harmful to humans.
  • Staphylococcus aureus causes diseases in humans such as cellulitis, furuncles, etc.
• Bacteria belonging to the genera Salmonella are harmful to humans.
  • Salmonellosis is a bacterial disease that affects the intestinal tract.
• Clostridium is a genus of bacteria that are known to be found in the intestinal tract of animals. 
  • In humans, they cause diseases such as botulism and tetanus.

So the correct answer is option 1 (Lactobacillus and Bifidobacterium).