Economic Importance of Bacteria

Name the four common shapes of bacteria.

Answer

1. Cocci (spherical bacteria)
2. Bacilli (rod-shaped bacteria)
3. Spirilla (twisted or spiral bacteria)
4. Vibrio (comma-shaped)

Give the technical terms for the following patterns of occurrence of bacteria

1. In pairs ...............
2. In long chains ...............
3. In clusters ...............

Answer

1. Diplococci
2. Streptococci
3. Staphylococci

List the kinds of nutrition in bacteria.

Answer

Bacteria mostly shows saprotrophic and parasitic nutrition.

What is the common method of reproduction in bacteria?

Answer

The common method of reproduction in bacteria is fission or cell division.

Why do bacteria produce spores ?

Answer

Bacteria produce spores to overcome unfavourable conditions.

Bacteria are no more classified as plants primarily because:

1. These are unicellular and prokaryotic
2. These are motile
3. Many of them are parasitic
4. They have no chlorophyll

Answer

These are unicellular and prokaryotic.

Reason — Bacteria are single-celled organisms that lack a nucleus and membrane-bound organelles. Unlike plants, which are multicellular and have eukaryotic cells, bacteria are classified as prokaryotes. This fundamental difference in cellular structure and organization led to their separation from the plant kingdom.
Some plants show movement too. Parasitism occurs in many plant-like organisms as well. Lack of chlorophyll is not universal—some bacteria do have photosynthetic pigments.

A particular species of which one of the following, is the source bacterium of the antibiotic, discovered next to penicillin, for the treatment of tuberculosis?

1. Escherichia
2. Streptomyces
3. Rhizobium
4. Nitrobacter

Answer

Streptomyces

Reason — Streptomycin was discovered next to penicillin by Selman Waksman. It was derived from Streptomyces griseus.
Escherichia is mainly studied as a model organism. Rhizobium helps in nitrogen fixation in plants. Nitrobacter is involved in the nitrogen cycle.

Which bacteria is rod shaped?

1. Coccus
2. Spirillum
3. Bacillus
4. Vibrio

Answer

Bacillus

Reason — Rod-shaped bacteria are called bacillus.
Coccus are spherical bacteria. They may occur singly or in groups. Spirillum are spiral or helical-shaped bacteria. They are usually rigid and move using flagella. Vibrio are comma-shaped bacteria.

Which bacteria fixes nitrogen in the soil?

1. Nitrobacter
2. Nitrosomonas
3. Rhizobium
4. Clostridium

Answer

Rhizobium

Reason — Rhizobium is the nitrogen fixing bacteria present in root nodules of legumes.
Nitrobacter converts nitrite into nitrate in the nitrogen cycle. It does not fix atmospheric nitrogen. Nitrosomonas converts ammonia into nitrite. It is not involved in nitrogen fixation. Clostridium are free-living, some species can fix nitrogen but not all.

Cell wall of bacteria is composed of:

1. Cellulose
2. Peptidoglycan
3. Glycogen
4. Lipoproteins

Answer

Peptidoglycan

Reason — The bacterial cell wall is made up of Peptidoglycan and not cellulose as in plants.
Cellulose is found in plant cell walls, not in bacteria. Glycogen is a storage form of glucose in animals and some microbes, not a structural component of bacterial cell walls. Lipoproteins may be present in membranes, but they are not the main structural material of bacterial cell walls.

Which of the following structures is suspended in the cytoplasm of a bacterial cell ?

1. Plasma
2. Capsule
3. Plasmid
4. Flagellum

Answer

Plasmid

Reason — Plasmid is a small circular DNA suspended in the Cytoplasm.
Plasma is the fluid matrix itself, not something suspended in it. Capsule is a protective layer outside the cell wall, not inside the cytoplasm. Flagellum is a tail-like structure used for movement, located outside the cell body.

Bacteria mainly reproduces by means of :

1. Multiple fission
2. Budding
3. Binary fission
4. Regeneration

Answer

Binary fission

Reason — Bacteria divides into two by simple cell division. This is known as binary fission.
Multiple fission involves one cell dividing into many at once. It is common in some protozoa. Budding occurs when a small outgrowth (bud) forms and detaches. It is seen in yeast and some organisms. Regeneration is the ability to regrow lost parts, seen in some multicellular organisms.

Bacteria are referred to as prokaryotes because:

1. They have no chlorophyll
2. They are unicellular
3. They are free living
4. They do not have a well defined nucleus enclosed in a nuclear membrane.

Answer

They do not have a well defined nucleus enclosed in a nuclear membrane.

Reason — The cells in which the nuclear membrane is absent is called prokaryotes.
Some bacteria have photosynthetic pigments. Many organisms are unicellular, but that alone does not make them prokaryotic. Some bacteria are free-living, others are parasitic or symbiotic.

Which of the following diseases can be prevented by TAB?

1. Tuberculosis
2. Typhoid
3. Tetanus
4. Taeniasis

Answer

Typhoid

Reason — TAB is the vaccine of Typhoid. It contains killed typhoid bacteria.
Tuberculosis is prevented by the BCG vaccine. Tetanus is prevented by the tetanus toxoid vaccine. Taeniasis is caused by parasites (tapeworms), not prevented by TAB.

A preparation consisting of weakened or dead germ substances is:

1. Toxins
2. Antitoxins
3. Toxoids
4. Vaccines

Answer

Vaccines

Reason — Vaccine consists of weakened or dead germ substances. Administration of vaccine results in resistance in body against the particular disease.
Toxins are poisonous substances produced by bacteria or other organisms. They are not used for immunization. Antitoxins are defensive antibodies produced in the body to neutralize toxins, not germ preparations. Toxoids are inactivated toxins used in some vaccines, but they are only a part of certain vaccines.

Certain free-living bacteria in the soil like (P) ............... and (Q) ............... use the free nitrogen of the soil and convert it to ammonia with hydrogen. P and Q are :

1. P — Rhizobium, Q — Azotobacter
2. P — Azotobacter, Q — Clostridium
3. P — Clostridium, Q — Rhizobium
4. P — Nitrosomonas, Q — Nitrobacter

Answer

P — Azotobacter, Q — Clostridium

Reason — Both Azotobacter and Clostridium are free-living nitrogen-fixing bacteria present in soil. They convert atmospheric nitrogen into ammonia.
Rhizobium lives in root nodules of leguminous plants, not freely in soil. It is not free-living. Nitrosomonas converts ammonia into nitrite. Nitrobacter converts nitrite into nitrate.

Name the following:

(a) The locomotory structure of a bacterium that enables it to swim.

(b) The process of flavouring tea by certain bacteria.

(c) The process of making leather from the animals skin.

(d) Bacterial disease of mustard.

(e) The scientist who discovered the antibiotic streptomycin.

Answer

(a) Flagella

(b) Curing

(c) Leather tanning

(d) Black rot of mustard

(e) Selman Waksman

Match the items in Column A with those in Column B

Answer

Fill in the blanks:

(a) The first antibiotic penicillin was discovered by ............... .

(b) ............... bacteria is found living in the nodules on the roots of leguminous plants.

(c) The hormone ............... was the first substance produced by Escherichia coli.

(d) ............... is an example of denitrifying bacteria.

(e) ............... and ............... are the two heterotrophic modes of nutrition in bacteria.

Answer

(a) The first antibiotic penicillin was discovered by Alexander Fleming.

(b) Rhizobium bacteria is found living in the nodules on the roots of leguminous plants.

(c) The hormone insulin was the first substance produced by Escherichia coli.

(d) Pseudomonas is an example of denitrifying bacteria.

(e) Saprotrophic and parasitic are the two heterotrophic modes of nutrition in bacteria.

Given below is the structure of a bacterial cell. Match the structures marked (a) to (e) with their function or characterstics given. Example; (f)-6 : Lies immediately beneath the cell wall and surrounds the cytoplasm.

Function/Characteristics

1. Protective layer
2. Locomotory structure.
3. Composed of DNA.
4. Made up of peptidoglycan.
5. Stored food material.
6. Lies immediately beneath the cell wall and surrounds the cytoplasm.

Answer

1. Flagellum - Locomotory structure
2. Nucleoid - Composed of DNA
3. Inclusion granules - Stored food material
4. Cell membrane - Lies immediately beneath the cell wall and Surrounds the cytoplasm
5. Capsule - Protective layer
6. Cell wall - Made up of peptidoglycan

Name the bacteria that converts

(a) ammonium compounds to nitrites

(b) nitrites to nitrates

Answer

(a) Nitrosomonas

(b) Nitrobacter

Given below is a flow chart of 'Nitrogen cycle'. Read the information after the diagram and fill in the blanks.
Nitrogen is one of the essential elements for the groMh and development of plants. About 79% of the atmosphere is Nitrogen but plants cannot obtain it directly from the atmosphere.

Plants can obtain nitrogen only in the form of nitrates, which they absorb from the soil through roots. These nitrates are replenished in the soil by bacteria through the process of (a) ............... . Some bacteria convert nitrogenous wastes of plants and animals into (b) ............... , which are then converted into (c) ............... compounds. Further, these compounds are converted into nitrites and nitrates by bacteria (d) ............... respectively.

Answer

(a) Nitrogen fixation

(b) Ammonia

(c) Ammonium compounds

(d) Nitrosomonas

In what form bacteria may be present in the air?

Answer

In air, bacteria can be present in the form of spores.

Why is spore formation in bacteria not considered a form of reproduction?

Answer

Spore formation in bacteria cannot be considered as a form of reproduction as they can reproduce through asexual means only such as cell division or fission. The formation of spores in bacteria is only an escape tactic from unfavorable condition that is exhibited by them.

In what respect do you consider bacteria as simple organisms?

Answer

Bacteria are unicellular organisms that lack membrane bound cell organelles like chloroplast, mitochondria, etc. and even a well-defined nucleus is absent which states that they have a simpler cellular organization.

Define the terms :

(a) Antibiotics

(b) Antitoxins

(c) Serum

(d) Botulism

(e) Pasteurization

Answer

(a) Antibiotics — An antibiotic is a chemical substance produced by a living microorganism which can stop the growth of or kill some disease-producing bacteria and fungi.

(b) Antitoxins — Antitoxin is a substance produced in animal bodies which reacts with the poison (toxin) produced by the invading germs.

(c) Serum — Serum actually means blood plasma from which fibrinogen has been removed. It may contain numerous chemical substances including anti-bodies and antitoxins.

(d) Botulism — Botulism is a very serious food poisoning due to a special bacterium sometimes found in tinned or sealed foods.

(e) Pasteurization — Pasteurization is the process of food preservation, applied usually to milk. In this process, the milk is heated at 60°C for 30 minutes and then chilled quickly. It kills majority of bacteria.

Give two examples of each :

(a) Bacterial diseases of cattle

(b) Bacterial diseases in plants

(c) Bacterial diseases in humans

(d) Nitrifying bacteria

(e) Free living nitrogen-fixing bacteria found in soil

Answer

(a) Anthrax and Bovine tuberculosis

(b) Bacterial blight of cowpea and Black rot of mustard

(c) Cholera and Tuberculosis

(d) Nitrosomonas and Nitrobacter

(e) Azotobacter and Clostridium

Write the full forms of the following abbreviations:

(a) TAB

(b) BCG

(c) DNA

(d) GMO

Answer

(a) TAB — Typhoid-paratyphoid A and B

(b) BCG — Bacille Calmette-Guerin

(c) DNA — Deoxyribonucleic Acid

(d) GMO — Genetically Modified Organism

Give reasons :

(a) Every room in the house should get direct sunlight at least for a short time.

(b) Tinned and sealed food is not always safe to eat.

Answer

(a) Direct sunlight contains ultraviolet radiations of the Sun, which help in killing of mould spores present in air. Hence, it is advised that every living room in the house should get direct sunlight at least for a short time.

(b) No, tinned and sealed food are not always safe to eat as it may contain harmful bacteria like Clostridium botulinum that causes food poisoning. Clostridium botulinum releases toxins under low-oxygen conditions. These toxins are very lethal and can block nerve functions leading to muscular and respiratory paralysis.
Moreover, the chemicals used in the inner coating of the container can be harmful for humans.

State the differences between:

(a) Decay and putrefaction.

(b) Pasteurization and sterilization of food/objects/equipments.

Answer

(a) Difference between Decay and Putrefaction:

(b) Difference between Pasteurization and Sterilization:

Would there be any bacteria in an aquarium?

Answer

Yes, bacteria can exist in aquarium. Bacteria can exist practically everywhere, as they can withstand any climatic condition.

How do bacteria obtain their nourishment?

Answer

Most bacteria are heterotrophic i.e. they depend on ready-made food from different sources. In this category, the bacteria maybe:

1. Saprophytic — Such bacteria draw nourishment from decaying dead organisms.
2. Parasitic — Such bacteria draw nourishment from the body of their living hosts.

The bacteria secrete powerful enzymes from their cells into the surrounding food containing material. The enzymes make the food material soluble which is then absorbed as a solution into the bacterial cell.

Describe any two uses of bacteria in industry.

Answer

Uses of bacteria in industry:

1. Tanning of leather — It is brought about by sunlight with the involvement of a few bacteria which breakdown the soft perishable parts of the skin.
2. Tea curing — Different flavours of tea are produced by certain bacteria.

What are antibiotics? Name any two examples.

Answer

Antibiotics are chemical substances produced by a living organism which inhibits or kills the growth of micro-organisms that cause the diseases such as fungi and bacteria. Examples of antibiotics are:

1. Streptomycin
2. Penicillin

Briefly describe how nitrogen of the atmosphere is converted to nitrates by leguminous plants.

Answer

A special category of soil bacteria (Rhizobium) is found living in small nodules on the roots of leguminous plants. These bacteria pick up free nitrogen from the soil and atmosphere and convert it into soluble nitrates. These nitrates are used by the host plant and also by other plants sown later in the same soil.

State how the nitrates in the soil get converted to nitrogen of the atmosphere.

Answer

Denitrifying bacteria in the soil break down nitrates present in the soil to release nitrogen gas which enters the atmosphere. Pseudomonas is an example of denitrifying bacteria.

Draw a diagram showing the Nitrogen cycle and answer the following questions.

(a) Define the terms:

1. Nitrification
2. Denitrification

(b) Distinguish between biological nitrogen fixation and industrial nitrogen fixation.

(c) Name the kind of relationship that exists between Rhizobium and leguminous plants.

Answer

(a) Below diagram shows the Nitrogen cycle:

1. Nitrification — The conversion of atmospheric nitrogen to nitrates is called nitrification.
2. Denitrification — The conversion of nitrates into atmospheric nitrogen is called Denitrification.

(b) Difference between biological nitrogen fixation and industrial nitrogen fixation are:

(c) Symbiotic relationship.

Assertion (A): Bacteria are the smallest living organisms on the earth without a well-defined nucleus.

Reason (R): The single circular chromatin material of a bacterial cell is not enclosed in a nuclear membrane.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Reason — A is true because bacteria are among the smallest living organisms and they do not have a well-defined nucleus.
R is true because in bacteria, the genetic material is a single circular DNA molecule and it is not enclosed by a nuclear membrane.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Assertion (A): Certain bacteria are saprotrophic in nature, meaning they draw their nourishment from another living being (host).

Reason (R): Parasitic bacteria draw their nourishment from the body of their living hosts.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is false but R is true

Reason — A is false because saprotrophic bacteria feed on dead and decaying organic matter, not on living hosts. Bacteria that feed on living hosts are called parasitic bacteria, not saprotrophic.
R is true because parasitic bacteria draw their nourishment from the body of their living hosts.

Therefore, A is false but R is true is the correct option.

Assertion (A): Clostridium is a type of bacteria found in the root nodules of leguminous plants. It converts soil nitrates into atmospheric nitrogen.

Reason (R): Clostridium is a free-living bacteria in the soil which converts soil nitrates into ammonia.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is false but R is true.

Reason — A is false because Root nodules of leguminous plants contain mainly Rhizobium, not Clostridium. Clostridium does not convert nitrates into atmospheric nitrogen.
R is true because Clostridium is a free-living anaerobic bacterium found in soil. It participates in nitrogen transformations, including reducing nitrogen compounds under anaerobic conditions.

Therefore, A is false but R is true is the correct option.

Assertion (A): Pasteurization is a technique of partial sterilization applied usually to milk.

Reason (R): Pasteurization kills a majority of the bacteria usually present in milk.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true and R is the correct explanation of A.

Reason — A is true because pasteurization involves heating milk to a specific temperature for a short time and then rapidly cooling it. It is called partial sterilization because it does not kill all microbes, only the harmful ones.
R is true because the process significantly reduces the number of pathogenic and spoilage bacteria.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Assertion (A): Black rot of mustard is a fungal disease whereas black rot of cauliflower is a viral disease'

Reason (R): Both black rot of mustard and cauliflower are bacterial diseases.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is false but R is true.

Reason — A is false Black rot of both mustard and cauliflower is caused by the bacterium Xanthomonas campestris. Hence, the assertion is incorrect because it wrongly states fungal and viral causes. The reason is correct as both diseases are bacterial.

Therefore, A is false but R is true is the correct option.

During a visit to her uncle's farm, Nazia noticed that the pea plants looked healthier than some of the other plants growing nearby. When she pulled out a small plant carefully, she observed tiny round structures on the roots. Her uncle explained that these structures are very useful for the soil. The organisms found inside these swollen, round structures improve the fertility of soil. Nazia was very curious to know the details of these swollen structures. She later learned all about it in her biology class.

(a) Write the scientific name of the organism found in these swollen parts of the root.

(b) What term is used to describe these swollen structures of the root ?

(c) Mention the category of the organisms, answered in (b) above.

(d) How do these organisms improve the fertility of the soil ? Name the process.

(e) Name two compounds which are produced during the above mentioned process.

Answer

(a) Rhizobium is the scientific name of the organism found in these swollen parts of the root.

(b) Root nodules is the term is used to describe these swollen structures of the root.

(c) The category of the organism is bacteria.

(d) These bacteria convert atmospheric nitrogen into usable nitrogen compounds for plants. This process is called nitrification.

(e) Two compounds which are produced during the process ammonia and nitrates.