Bacteria and its Economic Importance - Questions & Answers

Progress Check

1. Name the four common shapes of bacteria.
The four common shapes of bacteria are Cocci (spherical), Bacilli (rod-shaped), Spirilla (spiral or twisted), and Vibrio (comma-shaped).

2. Give the technical terms for the following patterns of occurrence of bacteria
(i) In pairs .....................
Diplococci
(ii) In long chains .....................
Streptococci
(iii) In clusters .....................
Staphylococci

3. List the kinds of nutrition in bacteria.
Most bacteria are heterotrophic, which includes two main types: saprotrophic (drawing nourishment from decaying dead organisms) and parasitic (drawing nourishment from the body of living hosts).

4. What is the common method of reproduction in bacteria?
The common method of reproduction in bacteria is asexual by means of binary fission or cell division.

5. Why do bacteria produce spores?
Bacteria produce spores as a method of escaping unfavourable conditions (such as extreme dryness, boiling water, freezing ice, or poisonous chemicals). Spores are resting stages that can withstand these harsh environments.

---

Review Questions

A. MULTIPLE CHOICE TYPE

1. Choose the correct answer from the options given below :

(i) Bacteria are no more classified as plants primarily because :
(a) they are unicellular and prokaryotic
(b) they are motile
(c) many of them are parasitic
(d) they have no chlorophyll.
Answer: (a) they are unicellular and prokaryotic

(ii) 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?
(a) Escherichia
(b) Streptomyces
(c) Rhizobium
(d) Nitrobacter
Answer: (b) Streptomyces

(iii) Which bacteria is rod shaped ?
(a) Coccus
(b) Spirillum
(c) Bacillus
(d) Vibrio
Answer: (c) Bacillus

(iv) Which bacteria fixes nitrogen in the soil ?
(a) Nitrobacter
(b) Nitrosomonas
(c) Rhizobium
(d) Clostridium
Answer: (c) Rhizobium (Note: Both Rhizobium and Clostridium fix nitrogen, but Rhizobium is the classic symbiotic nitrogen-fixing bacteria commonly referred to in this context)

(v) Cell wall of bacteria is composed of :
(a) Cellulose
(b) Peptidoglycan
(c) Glycogen
(d) Lipoproteins
Answer: (b) Peptidoglycan

(vi) Which of the following structures is suspended in the cytoplasm of a bacterial cell ?
(a) Plasma
(b) Capsule
(c) Plasmid
(d) Flagellum
Answer: (c) Plasmid

(vii) Bacteria mainly reproduces by means of :
(a) Multiple fission
(b) Budding
(c) Binary fission
(d) Regeneration
Answer: (c) Binary fission

(viii) Bacteria are refered to as prokaryotes because:
(a) They have no chlorophyll
(b) They are unicellular
(c) They are free living
(d) They do not have a well defined nucleus enclosed in a nuclear membrane.
Answer: (d) They do not have a well defined nucleus enclosed in a nuclear membrane.

(ix) Which of the following diseases can be prevented by TAB ?
(a) Tuberculosis
(b) Typhoid
(c) Tetanus
(d) Taeniasis
Answer: (b) Typhoid

(x) A preparation consisting of weakened or dead germ substances is :
(a) Toxins
(b) Antitoxins
(c) Toxoids
(d) Vaccines
Answer: (d) Vaccines

(xi) 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 :
(a) P — Rhizobium       Q — Azotobacter
(b) P — Azotobacter      Q — Clostridium
(c) P — Clostridium      Q — Rhizobium
(d) P — Nitrosomonas   Q — Nitrobacter
Answer: (b) P — Azotobacter      Q — Clostridium

B. VERY SHORT ANSWER TYPE

1. Name the following :
(a) The locomotory structure of a bacterium that enables it to swim.
Flagellum
(b) The process of flavouring tea by certain bacteria.
Tea curing
(c) The process of making leather from the animals' skin.
Leather tanning
(d) Bacterial disease of mustard.
Black rot of mustard
(e) The scientist who discovered the antibiotic streptomycin.
Selman Waksman

2. Match the items in Column A with those in Column B.
Column A                      Column B
(i) Penicillium                (a) Bacteria occurring in chains.
(ii) Diplococci                (b) Antibiotic.
(iii) Streptococci            (c) Bacteria occurring in pairs.
Answer:
(i) Penicillium — (b) Antibiotic.
(ii) Diplococci — (c) Bacteria occurring in pairs.
(iii) Streptococci — (a) Bacteria occurring in chains.

3. Fill in the blanks :
(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.

4. Given below is the structure of a bacterial cell. Match the structures marked (a) to (e) with their function or characteristics given.
Function/Characteristic:
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:
(a) Flagellum — 2. Locomotory structure.
(b) Bacterial chromosome — 3. Composed of DNA.
(c) Glycogen granules — 5. Stored food material.
(d) Cell wall — 4. Made up of peptidoglycan.
(e) Capsule — 1. Protective layer.

C. SHORT ANSWER TYPE

1. In what form bacteria may be present in the air?
Bacteria may be present in the air in the form of spores.

2. Why is spore formation in bacteria not considered a form of reproduction ?
Spore formation in bacteria is not a method of reproduction because it does not result in an increase in the number of individuals. It is simply a method of escaping unfavourable conditions by forming a hard protective wall to survive until conditions become favourable again.

3. In what respect do you consider bacteria as simple organisms ?
Bacteria are considered simple organisms because they are unicellular, primitive prokaryotes that lack a true well-defined nucleus and a nuclear membrane. Their genetic material is simply dispersed in the central region of the cytoplasm.

4. Define the terms :
(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 to neutralize their effect.
(c) Serum
Serum is blood plasma from which fibrinogen has been removed, containing chemical substances like antibodies and antitoxins for a particular pathogen used as a preventive measure against bacterial invasion.
(d) Botulism
Botulism is a very serious food poisoning caused by a special bacterium sometimes found in poorly sealed tinned and sealed foods.
(e) Pasteurization
Pasteurization is a technique of partial sterilization applied usually to milk, where it is heated to a temperature of about 60°C for a period of 30 minutes and then chilled quickly to kill a majority of bacteria.

5. Name the bacteria that converts
(a) ammonium compounds to nitrites
Nitrosomonas
(b) nitrites to nitrates.
Nitrobacter

6. 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 growth 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) nitrification. Some bacteria convert nitrogenous wastes of plants and animals into (b) ammonia, which are then converted into (c) ammonium compounds. Further, these compounds are converted into nitrites and nitrates by bacteria (d) Nitrosomonas and (e) Nitrobacter respectively.

(Note: The textbook repeats question numbers 5 and 6 in the right column. Maintaining sequence exactly as printed)

5. Give two examples of each :
(a) Bacterial diseases of cattle
Anthrax, Bovine tuberculosis
(b) Bacterial diseases in plants
Black rot of mustard, Bacterial blight of cowpea
(c) Bacterial diseases in humans
Cholera, Typhoid
(d) Nitrifying bacteria
Nitrosomonas, Nitrobacter
(e) Free living nitrogen - fixing bacteria found in soil
Azotobacter, Clostridium

6. Write the full forms of the following abbreviations :
(a) TAB
Typhoid-Paratyphoid A and B Vaccine (or TAB vaccine for typhoid)
(b) BCG
Bacillus Calmette-Guérin
(c) DNA
Deoxyribonucleic Acid
(d) GMO
Genetically Modified Organism

7. Give reasons :
(a) Every room in the house should get direct sunlight at least for a short time.
Because sunlight contains ultra-violet light which is useful in naturally sterilizing the air by killing bacteria and mold spores, preventing the spread of diseases.
(b) Tinned and sealed food is not always safe to eat.
Because if the tins are poorly sealed, a special bacterium can grow inside them causing a very serious food poisoning known as Botulism, which produces gas and spoils the food.

8. State the differences between
(a) Decay and putrefaction.
Decay is the complete breakdown of organic matter by bacteria without giving out a foul smell. Putrefaction is the incomplete breakdown of organic matter by bacteria, emitting a foul smell.
(b) Pasteurization and sterilization of food/objects/equipments.
Pasteurization is a partial sterilization technique (usually heating to 60°C and chilling quickly) that kills a majority of bacteria but does not completely sterilize. Sterilization uses much higher temperatures (like boiling at 100°C or autoclave at 110°C) to completely kill all bacteria and their spores.

9. Would there be any bacteria in an aquarium ?
Yes, bacteria would be present in an aquarium. They are necessary natural scavengers that break down the organic excreta and dead matter from the fish and plants in the water, completing the process of decay and putrefaction.

D. LONG ANSWER TYPE

1. How do bacteria obtain their nourishment ?
Most bacteria have no chlorophyll, so they are heterotrophic and depend on readymade food. They obtain their nourishment primarily in two ways: by being saprotrophic (drawing nourishment from decaying dead organisms) or parasitic (drawing nourishment from the body of living hosts). They secrete powerful enzymes into the surrounding food material to make it soluble, which is then absorbed as a solution into the bacterial cell.

2. Describe any two uses of bacteria in industry.
(1) Curing of tea: Certain bacteria are used to produce different and specific flavours of tea.
(2) Leather tanning: Bacteria are used in breaking down the soft perishable parts of animal skin (hide) to help process it into leather.

3. What are antibiotics ? Name any two examples.
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. Examples of antibiotics include Penicillin and Streptomycin.

4. Briefly describe how nitrogen of the atmosphere is converted to nitrates by leguminous plants.
A special category of symbiotic soil bacteria called Rhizobium is found in small nodules on the roots of leguminous plants (like beans). These bacteria pick up free nitrogen directly from the soil and the atmosphere and convert it into soluble nitrates. These nitrates are then readily used by the host plant for growth and synthesizing proteins.

5. State how the nitrates in the soil get converted to nitrogen of the atmosphere.
Nitrates in the soil are broken down by denitrifying bacteria (such as Pseudomonas) present in the soil. These bacteria decompose the soil nitrates to release pure nitrogen gas, which escapes back into the atmosphere in a process called denitrification.

E. STRUCTURED/APPLICATION/SKILL TYPE

1. Draw a diagram showing the Nitrogen cycle and answer the following questions.
(a) Define the terms :
(i) Nitrification
Nitrification is the process by which bacteria replenish nitrates in the soil by first converting the nitrogenous wastes of animals and dead remains of plants (ammonia) into nitrites, and then into nitrates.
(ii) Denitrification
Denitrification is the process where specific bacteria in the soil break down soil nitrates to release pure nitrogen gas back into the atmosphere.
(b) Distinguish between biological nitrogen fixation and industrial nitrogen fixation.
Biological nitrogen fixation is naturally carried out by living microorganisms (like Rhizobium) which convert free atmospheric nitrogen into soluble nitrates in the soil. Industrial nitrogen fixation is the artificial chemical process of fixing nitrogen in factories to produce fertilizers.
(c) Name the kind of relationship that exists between Rhizobium and leguminous plants.
Symbiotic relationship.

F. ASSERTION – REASON TYPE QUESTIONS:

(Choose the answer based on the codes given below.)
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

(i) 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.
Answer: (a) Both A and R are true and R is the correct explanation of A.

(ii) 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.
Answer: (d) A is false but R is true.

(iii) 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.
Answer: (d) A is false but R is true. (Note: Based strictly on the provided MCQs structure; however logically Clostridium converts free nitrogen into ammonia, not soil nitrates)

(iv) 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.
Answer: (a) Both A and R are true and R is the correct explanation of A.

(v) 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.
Answer: (d) A is false but R is true.

G. CASE STUDY BASED QUESTION

1. 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.
Rhizobium
(b) What term is used to describe these swollen structures of the root ?
Root nodules
(c) Mention the category of the organisms, answered in (b) above.
Symbiotic nitrogen-fixing bacteria
(d) How do these organisms improve the fertility of the soil ? Name the process.
They improve soil fertility by picking up free nitrogen from the soil and atmosphere and converting it into soluble nitrates which enrich the soil. The process is Biological Nitrogen Fixation.
(e) Name two compounds which are produced during the above mentioned process.
Ammonia and Nitrates

WOULD THERE BE ANY BACTERIA IN AN AQUARIUM ?

A balanced aquarium contains certain animals as well as some plants. How many kinds of animals can you make out in the aquarium shown here ? Name any two such animals.
Two kinds of animals visible in the aquarium ecosystem are Fishes and Snails.

Do you think there would be some bacteria in it ? If so, in which part of the aquarium would they be occurring in abundance and what for ?
Yes, there are bacteria present in the aquarium. They would be occurring in abundance at the bottom soil/gravel and around dead matter or waste. They are present as scavengers to decay and putrefy the organic excreta and dead bodies of aquatic life, breaking them down into simpler chemical compounds.