KINGDOM PROKARYOTAE (MONERA)

Biology XI Notes
Kingdom Prokaryotae (Monera) - Short Questions Answers

Chapter # 06
Biology - XI
Section III - Biodiversity

KINGDOM PROKARYOTAE (MONERA)

Q.1: What are Bacteria? What are the types of Bacteria?

Ans: BACTERIA:

Bacteria are the simplest and smallest living organisms which possess cellular structure. They are microscopic. They were discovered by a Dutch scientist Anton Von Leeuwenhoek in 1676, then he gave them the name bacteria in 1683.

Some microbiologists have placed bacteria in two groups:
Eubacteria:
It is a large division. These bacteria are the true bacteria.

Archaeabacteria:
It is a smaller division. These are ancient bacteria.

(Diagram: Types of Bacteria)

• Coccus

  • Micrococcus
  • Diplococci
  • Streptococci
  • Staphylococci

• Bacillus

  • Microbacillus
  • Diplobacilli
  • Streptobacilli
  • Staphylobacilli

• Spiral

  • Spiral
  • Vibrio

The size of bacteria is very small, ranges from 0.5 microns to 2 microns. They are found everywhere, in soil, water and air. They do not have chlorophyll, so they live as parasites in plants and animals or saprophytes on dead organic substances

TYPES OF BACTERIA:

There are four types of bacteria.
Cocci:
They are spherical in shape. According to the arrangement, they are of following types.

• Micrococcus:
  They are single, not arranged in groups.
• Diplococci:
  They are found in groups of two.
• Streptococci:
  They are arranged in chain-like manner.
• Sarcina:
  Group of eight bacteria, also called octant.
• Staphylococci:
  They are present in bundles or groups.
• Tetrad:
  Group of four bacteria.

Bacilli:
They are rod-shaped bacteria. They may also be found (i) Singly, called microbacillus, (ii) in group of two, called diplobacilli, (iii) arranged in a chain, streptobacilli, (iv) In groups of many known as staphylobacilli.

Spirilli:
These are spiral or corkscrew-shaped bacteria. They are never found in groups, e.g., Spirocheta.

Vibrio:
They are comma-shaped. They are also not found in groups.

Q.2: Describe the structure of Bacterial cell?

Ans: STRUCTURE OF BACTERIA:
Bacteria are simplest and smallest living organisms. The size of bacterial cell is 0.2 micron (µ) to 2µ in breadth and 2 to 10µ in length.

Bacteria are unicellular but may form groups or colonies.
A bacterial cell consists of following parts:

• Flagella
• Pilli
• Capsule
• Cell wall
• Cell membrane
• Cytoplasm
• Mesosomes
• Nucleoid (Nuclear material)
• Plasmi
• Flagella:
• Flagella are thin hair-like structures arise from basal body, a structure present beneath the cell membrane. Flagella are locomotory organs of bacteria i.e., help in the movement of the body.

• Pilli:
  These are fine, hollow, filament-like structures. These are not used in locomotion, but help in conjugation process of reproduction.

  Capsule:
  It is an additional protective layer around the cell wall and found in some bacteria, it is composed of polysaccharides and proteins. In some bacteria slime-capsule is present, which is used for the protection of bacterial cell against phagocytosis and increases the activity of bacterial cell.

  Cell wall:
  It is present around the bacterial cell. It is composed of amino acids, sugars and chitin. Cellulose is not present in bacterial cell. In some bacteria capsule is also present around the cell wall. In the cell wall of bacteria a compound is present, called peptidoglycan. It helps to maintain the cell shape and provides strength. It surrounds the cell wall like a network.

  Cell Membrane:
  Internal to the cell wall cell membrane or plasma membrane is present. The protoplasm of bacterial cell is bounded by cell membrane. It is composed of lipids and proteins. Cell membrane is semi-permeable and responsible for the osmotic behavior of the cell. Cell membrane also acts as respiratory structure due to the absence of mitochondria.

  Cytoplasm:
  The cytoplasm is a fluid material. It is dense and contains granules of glycogen, proteins and fat. Mitochondria and endoplasmic reticulum are absent. In the cytoplasm ribosomes are present. They are small minute granules composed of protein and R.N.A. and help in protein formation.

  Mesosomes:
  The plasma membrane of bacterial cell is folded inward to form a special structure, called mesosomes. The mesosomes take part in cell division, DNA-replication, secretion of certain enzymes, respiration and active transport of enzymes.

• Nucleoid:
  In bacteria there is no complete nucleus, but it contains nuclear material called Nucleoid. It is an irregular-shaped dense structure called chromatin body or bacterial chromosome. It does not contain nuclear membrane, nucleoplasm and nucleolus. Due to the absence of a complete nucleus the bacterial cell is called prokaryotic cell.

  Plasmid:
  It is a small fragment of extra genetic material double stranded DNA. It replicates itself. It does not take part in growth and metabolism. It is used as vector in genetic engineering.

• Q.3: Describe the diversity of bacteria?

  Ans: DIVERSITY OF BACTERIA:

  Types On The Base Of Flagella:
  On the basis of flagella the bacteria are classified into different groups:

  • Atrichous:
    These bacteria are without flagella.
  • Monotrichous:
    These bacteria contain one polar flagellum.
  • Lophotrichous:
    These bacteria contain a tuft of flagella only at one pole.
  • Amphitrichous:
    These bacteria contain tuft of flagella at two poles of the body.
  • Peritrichous:
    These bacteria contain flagella around the whole cell.

  Gram-Positive And Gram-Negative:
  A Danish Microbiologist Hans Christian Gram discovered a violet dye for the identification of unknown bacteria. On the basis of this dye (color) bacteria are classified into two groups:

  • Gram-Positive Bacteria:
    These bacteria are stained with violet dye.
  • Gram-Negative Bacteria:
    These bacteria are not stained with violet dye.

  Some microbiologists have placed bacteria in two groups:

• Eubacteria:
  It is a large division. These bacteria are the true bacteria.
• Archaeabacteria:
  It is a smaller division. These are ancient bacteria.

Q.4: Describe the nutrition in bacteria?

Ans: There are different types of bacteria according to their nutrition.

• Autotrophic bacteria
• Heterotrophic bacteria
• Symbiotic bacteria

Autotrophic Bacteria:
The bacteria which utilize $\text{CO}_2$ and get energy from sunlight or from some chemical reactions are called autotrophic bacteria. They can synthesize organic compounds. They may be further divided into two groups.

• Photosynthetic Autotrophs:
  These bacteria have chlorophyll dispersed in the cytoplasm. They utilize the atmospheric $\text{CO}_2$ and get energy from sunlight and perform the process of photosynthesis, but they use hydrogen sulphide ($\text{H}_2\text{S}$) instead of water to get hydrogen, thus they release sulphur instead of oxygen.

  $$\text{CO}_2 + 2\text{H}_2\text{S} \xrightarrow{\text{Light, Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 2\text{S}$$

• Chemo-Autotrophs or Chemosynthetic Bacteria:
  These bacteria get energy by the oxidation and reduction process of various inorganic compounds, such as nitrates, ammonia, sulphur, ferrous ions, etc., so they are known as chemosynthetic bacteria.

Heterotrophic Bacteria:
These bacteria take their food from other living or non-living substances. These are of two types:

• Parasites:
  These bacteria obtain their food from the body of living organisms. They live in another organism and are fully dependent on the host. These bacteria cause diseases in the host and sometimes death occurs.

• Saprophytes:
  They obtain their food from dead organic substances. The soil humans are formed from the decay of plants and animals and it contains organic compounds. The bacteria change these compounds into simpler ones and get energy by this process.

Symbiotic Bacteria:
Some bacteria form an association with other organisms and both get benefits from each other; such bacteria are called symbiotic bacteria. For example, Rhizobium radicicola bacteria live in the roots of leguminous plants (e.g., Pea plant). These bacteria convert nitrogen into its compounds, Nitrites and Nitrates. This process is called nitrogen fixation. As a result of this process, bacteria get food material from plants. Such bacteria are called symbiotic bacteria.

Q.5: Describe the respiration in bacteria?

Ans: According to the respiration, there are two types of bacteria.

• Aerobes:
  These bacteria need oxygen for respiration. Aerobes bacteria are of two types:

  • Obligate Aerobes:
    These bacteria require $\text{O}_2$ and die in its absence.
  • Facultative Aerobes:
    These bacteria use $\text{O}_2$, but can also survive in its absence.

  The bacteria which require a little amount of $\text{O}_2$ are called Microaerophilic bacteria.

• Anaerobes:
  These bacteria do not need $\text{O}_2$ for respiration. Anaerobe bacteria are of different types:

• Obligate Anaerobes:
  Some bacteria are killed in the presence of $\text{O}_2$. These are called obligate anaerobes.
• Facultative Anaerobes:
  The bacteria which use $\text{O}_2$ but also can respire without it, they are called facultative anaerobes.

Q.6: Describe the locomotion in bacteria?

Ans: From the body of many bacteria whip-like bodies are produced, called flagella. They help in locomotion. They differ in number and distribution. In some bacteria, only one flagellum is present at the terminal side, while in others, the body is completely covered by flagella. Mostly bacilli and spirilli bacteria are motile, and cocci are non-motile.

According to the movement, the bacteria are of different types, such as:

• Phototactic Bacteria:
  These bacteria move towards or away from light.
• Chemotactic Bacteria:
  These bacteria move towards or away due to the presence of chemicals.
• Magnetotactic:
  These bacteria are able to detect magnetic fields of the earth.

Q.7: Describe the growth in bacteria?

Ans: Growth is an increase in the number of cells and size of cells. Bacteria take their food from the environment by diffusion or active transport process. Oxygen is required for aerobic bacteria, and it is not needed for anaerobic bacteria. The factors which affect the growth are:

• Temperature
• Available nutrients
• pH
• Ionic concentration

Stages or Phases of Growth:
In bacteria, there are four phases of growth:

• Lag Phase:
  This is the inactive phase of bacteria. In this stage, bacteria prepare themselves for growth. The cells accumulate essential substances such as water and proteins.

• Log Phase:
  The logarithmic phase (Log phase) is the period in which bacteria grow very rapidly. Their metabolic activities are maximum. Their rate of reproduction is more, and the rate of death is very slow, so they increase their number rapidly.

• Stationary Phase:
  After an active growth phase, bacteria face a shortage of food, pH changes, and energy loss, so they try to maintain themselves. They also start dying as a result of which their multiplication is equal to their death rate. The number of cells is almost unchanged, so it is called the stationary phase.

• Death Phase:
  When conditions are totally unfavorable, death occurs rapidly among growing cells. When the death rate is faster than the multiplication rate, it is called the death phase.

Q.8: Describe the process of binary fission in bacteria?

Ans: In this process, the parental cell divides into two daughter cells. First, the nucleus (nuclear material) divides into two nuclei, and bacterial cell elongates, and a constriction develops in the middle. One nucleus migrates into each separate area of the cell. The plasma membrane grows inwards, and the cell also divides into two daughter cells. The two daughter cells have the same properties as the parent cell.

Q.9: Describe genetic recombination in bacteria?

Ans: Genetic Recombination: (Sexual Reproduction)
There is no sexual reproduction in bacteria in a true or definite form, but a combination of two genetic materials takes place by certain methods. These are considered as sexual reproduction. These methods are of three types:

• Conjugation:
  When two changed forms of the same bacteria are kept together, the genetic material of one bacterial cell is transferred into another bacterial cell through a tube; the conjugating.

The process is known as conjugation. Conjugation method was reported by two scientists Joshua Lederberg and Edward Tatum in 1946. They got Nobel prize for their work. Joshua Lederberg and Edward Tatum observed conjugation between two strains of the common intestinal bacterium Escherichia coli.

Transduction:
In this process, the genetic material of one bacterial cell is transferred into another cell through bacteriophage virus. This process was reported by Lederberg and Zinder in 1952.

Transformation:
When the genetic information of one bacterium is transmitted into another bacteria and due to this information bacterium undergoes changes i.e., its nature is transformed, the process is called transformation.

This process was reported by an English scientist Fred Griffith in Pneumococcus bacteria.

Q.10: Describe the endospore formation in bacteria?

Ans: Some bacteria, especially the rod-shaped ones, have the ability to form endospores during unfavorable conditions. In this process, the protoplasm shrinks and forms a rounded mass. It is covered by a thick wall. It is known as an endospore.
The endospore is extremely resistant to heat, chemicals, freezing, and dryness. It may remain for a long time. Under favorable conditions, the endospore germinates into a single bacterial cell.

Q.11: Describe the importance of bacteria?

Ans: Bacteria have both positive and negative importance. They play a very important role in the life of human beings.

Positive Importance:

• Decaying of Dead Bodies (Decomposers):
  Bacteria decompose the dead remains of plants, animals, and human beings into simpler compounds. In this way, they help to clean the world.

• Bacteria in Industries:

• Bacteria are used in the dairy industry. They change milk into curd.
• They are used in the formation of butter and cheese from milk.
• They are used in the ripening of tobacco leaves.
• Bacteria are used in the preparation of alcohol and vinegar.
• Bacteria are also used in the leather industry.

• Digestion in Alimentary Canal:
  Certain bacteria are present in the intestine of man and help in the digestion of cellulose by an enzyme called cellulase.

• Fertility of Soil:
  Bacteria increase the fertility of soil by adding organic substances due to the decomposition of dead bodies.

• Genetic Engineering (Bio-Technology):
  Bacteria are used in genetic engineering. Escherichia coli bacteria are used to produce growth hormones and the production of insulin.

• Medical Bacteria:
  From bacteria, many important antibiotics have been obtained, such as Terramycin, Streptomycin, Neomycin, Thyrothrycin, Subtilin, Riboflavin, which is a vitamin produced by Clostridium bacteria.

• Nitrogen Fixation:
  Bacteria change nitrogen into its compounds like $\text{NO}_2$ and $\text{NO}_3$; this process is called nitrogen fixation.

Negative Importance:

• Spoilage of Food:
  Bacteria spoil our food stuff in large amounts by chemical processes. It is a great loss.

• Diseases in Man:
  Bacteria are responsible for causing various diseases in man and other animals, such as tuberculosis (T.B.), pneumonia, cholera, typhoid, tetanus, syphilis, diphtheria, etc.

• Diseases in Plants:
  Bacteria also cause diseases in various plants, such as citrus canker, fire blight of apple, ring disease of potato, wilt of solanaceae plants, etc.

Q.12: Write a note on control of bacteria?

Ans: Control of Bacteria:
When the infection of pathogenic organisms is brought to the minimum limit in a population, it is called control of these pathogenic organisms. It is necessary for the control of diseases, protection of food from spoilage, and also to prevent the damage of industrial products.

The different methods to control the infectious microorganisms are as follows:

• Infected persons should be properly treated by effective medicines.
• Persons in a population should be treated by immunization and vaccination.
• In epidemic conditions, the infected persons should be kept in quarantine to avoid the spread of infection to healthy persons.
• At different possible stages, the life cycle of pathogens should be disrupted, so it cannot cause further infection.
• The host bodies of pathogens should be identified and treated well to control the disease.
• By different ways, knowledge and awareness about diseases and infections of pathogens should be provided to the public.
• Many methods should be used to kill or inhibit the infection of pathogens, such as:
• High-temperature treatment
• By ultraviolet rays
• By the use of antiseptics
• By the use of antibiotics
• By chemotherapy

Q.13: What are immunization and vaccination?

Ans: Immunization and Vaccination:
The resistance against infection by pathogenic organisms is called immunity. It can be developed in the body by different ways. One method to develop immunity is vaccination or active immunization. Vaccination is used to control many diseases. A vaccine is either used orally, e.g., Polio vaccine, or taken into the body by syringe, e.g., Tetanus vaccine.

The procedure of vaccination is very effective and beneficial for human beings because it helps to control many dangerous diseases such as measles, diphtheria. When a large proportion of the population is immune, then the disease spreads poorly throughout the population.

Q.14: What are the uses and misuses of antibiotics?

Ans: Use and Misuse of Antibiotics:
Antibiotics are the chemical substances which are used to kill microorganisms that cause infectious diseases. These are produced by certain microorganisms and prevent the activity of other microorganisms.

The first antibiotic is Penicillin, which was isolated from Penicillium fungus in 1940. After that, a great work has been done in this field, and many antibiotics have been isolated or synthesized for the treatment of infectious diseases.

Use of Antibiotics:

• Antibiotics have their effect against the bacteria and kill them and control their infection.
• The antibiotics are used as vaccination to develop resistance in the body. They maintain the immune system.
• Antibiotics are also used in agriculture to kill different organisms. These are also used in animal feeds to provide growth-promoting substances.

Misuse of Antibiotics:

• By the extensive use of antibiotics, more resistance is developed in pathogenic microorganisms; after that, they cause more serious infection in the body.
• Antibiotics have many side effects. Other organs of the body may be damaged, such as liver cells and kidney cells.
• Antibiotics may react with human metabolism, and in severe cases, death of a person may occur.
• Some antibiotics cause allergy in the body, such as Penicillin.

Q.15: Write a note on Cyanobacteria? (Blue-green algae)

Ans: Cyanobacteria (Blue-Green Algae):
Important Characters:

• They are water-living simple organisms.
• They are prokaryotes, i.e., they do not have a true nucleus, like bacteria, so-called cyanobacteria.
• They contain blue-green pigments, chlorophyll a (green) and phycocyanin (blue), so they are also called blue-green algae.
• They are unicellular or may be found in groups or colonies.
• They have a double-layered cell wall.
• Their cytoplasm is differentiated into two parts:
  • Outer colored part, Chromoplasm with green and blue pigments.
  • Inner color part, Centroplasm.
• Asexual reproduction takes place by hormogonia, fragmentation, akinetes, or zoospores.
• Sexual reproduction is absent.

Q.16: Describe the structure and reproduction of Nostoc?

Ans: Nostoc belongs to the group Cyanophyta of Kingdom Monera. It is found in freshwater ponds, streams, lakes, etc.

Structure:

• The body of Nostoc is called Thallus. It is very simple in structure. The thallus consists of many thread-like bodies, known as filaments. Each filament is unbranched and composed of many spherical cells, which are arranged in beaded form. All the cells are similar in structure. The whole filament is covered by a gelatinous sheath, which protects the filament. The gelatinous mass is in colony form, called coenobium.
• In the filament of Nostoc, some larger, light-yellowish and thick-walled cells are also present, called heterocysts. The heterocysts take part in reproduction and nitrogen fixation. They convert nitrogen into its simpler form, which is easily utilized by the plant.

Structure of a Cell:

• Each cell of Nostoc is spherical in shape. It is covered by a double-layered wall. The outer layer of the cell wall is thick, composed of cellulose and pectic compounds. The inner layer is thin, composed of purely cellulose.

The protoplasm of the cell consists of two parts:

• Chromoplasm:
  It is the outer colored part. It contains color pigments, chlorophyll a, phycocyanin, xanthophyll, and carotene. These pigments are not found in plastids, but around this region, a plasma membrane is present.

• Centroplasm or Central Body:
  It is the inner part of protoplasm. It is colorless but stores food material in the form of cyanophycean starch. In Nostoc, endoplasmic reticulum, mitochondria, Golgi bodies, and vacuoles are absent, but ribosomes and pseudovacuoles are present.

  In the cell of Nostoc, a true nucleus is absent, but the central body acts like a nucleus and controls all the functions. It is an incomplete nucleus because it does not have a nuclear membrane and nucleolus, so it is also called an incipient nucleus. Due to the presence of an incomplete nucleus, the cell of Nostoc is considered a prokaryotic cell.

Nutrition:
Nostoc contains chlorophyll, so it can manufacture its own food material, i.e., it is autotrophic. It also takes part in nitrogen fixation, i.e., it converts nitrogen into nitrates by heterocyst.

Reproduction:
In Nostoc, the reproduction takes place by the following methods:

• By Hormogonia:
  The filament of Nostoc breaks up into many pieces, called hormogonia. Each hormogonium grows into a new filament.

• By Arthrospores or Akinetes:
  During unfavorable conditions, some cells of Nostoc filament become enlarged, and they are covered by a thick wall. They are called akinetes or arthrospores or resting spores. They also store food material. They take rest and germinate during favorable conditions into new filaments.

• By Heterocyst:
  The heterocysts also take part in reproduction. They are separated from the filament and change themselves into reproductive cells. (Each heterocyst develops into a new filament by cell division.)

• Q.17: What is the importance of Cyanobacteria?

• Ans: Importance of Cyanobacteria:

• These organisms take part in nitrogen fixation. Nostoc and Anabaena are used as nitrogen fertilizers in agriculture to improve soil fertility.
• During photosynthesis, they use $\text{CO}_2$ and $\text{H}_2\text{O}$. They release oxygen as a byproduct. In this way, they take part in changing and flourishing the environment.
• Many organisms of cyanobacteria are found in the form of phytoplankton. They are used as food by many aquatic animals.
• They also produce an unpleasant smell in water and make it unsuitable for drinking.

Q.18: Distinguish between the following?

Ans: Flagella and Pili:

Flagella	Pili
These are extremely thin appendages in bacterial cells.	These are hollow filamentous appendages in bacterial cells.
These are larger in size.	These are smaller than flagella.
They originate from a basal body, a structure in the cytoplasm beneath the cell membrane.	They do not originate from a basal body .
They help in locomotion. Photosynthetic Bacteria and Chemosynthetic Bacteria: Photosynthetic Bacteria Chemosynthetic Bacteria These bacteria contain chlorophyll. These bacteria do not contain chlorophyll. They use sunlight during photosynthesis. They do not use sunlight. They manufacture their food by the use of $\text{CO}_2$ and $\text{H}_2\text{S}$. They do not manufacture their food, but they use chemical substances, taking part in their oxidation and reduction to get energy. They use sulfur, called green sulfur bacteria. They use different inorganic chemical substances.	They help in conjugation, which is a process of reproduction