Class 11 Biology • Introductory Microbiology • Chapter 3.1

Class 11 Biology – Kingdom Monera Notes

Complete notes on Kingdom Monera, bacteria, bacterial structure, nutrition, economic importance, cyanobacteria and Nostoc.

📖 Original Handwritten Notes

Kingdom Monera

Kingdom Monera includes simple and primitive organisms which lack a well-developed nucleus and membrane-bound organelles.

Characteristics of Monera

They include simple and primitive organisms lacking a well-developed nucleus and membrane-bound organelles.
Their nuclear material consists of circular, double-stranded naked DNA present directly in the cytoplasm.
They are microscopic and composed of prokaryotic cells.
They are cosmopolitan in distribution and occur in different types of habitats.
Most possess a rigid cell wall.
Both autotrophic and heterotrophic modes of nutrition occur.
They act as important decomposers and mineralizers in the biosphere.
Reproduction is primarily asexual.

Classification of Monera

According to the classification presented in the handwritten notes, Kingdom Monera is divided into:

Eubacteria

Eubacteria are described as true bacteria.

The notes further include:

Bacteria
Cyanobacteria or blue-green algae

Archaebacteria

Archaebacteria are described as ancient bacteria.

Classification of Kingdom Monera

Bacteria

Bacteria are tiny, unicellular, microscopic prokaryotic organisms identified by their specific characteristics.

The notes state that bacteria were discovered by Antonie van Leeuwenhoek. The study of bacteria is called bacteriology.

Characteristics of Bacteria

Bacteria are unicellular and prokaryotic organisms.
They contain circular, double-stranded naked DNA as their primitive nuclear material.
They are cosmopolitan in distribution.
Most possess a rigid cell wall.
According to the source notes, the bacterial wall contains acetyl glucosamine and acetyl muramic acid together with diaminopimelic acid.
They may have autotrophic or heterotrophic nutrition.
They function as decomposers and mineralizers in the biosphere.
Flagella, when present, are single-stranded structures.
Ribosomes are of the 70S type.
The common mode of reproduction is binary fission.

Types of Bacteria on the Basis of Shape

1. Bacillus

Cylindrical and rod-like bacteria are known as bacilli.

Diplobacillus

Two bacilli occur in pairs. The source gives Corynebacterium diphtheriae as an example.

Streptobacillus

Many bacilli occur in chains. The handwritten notes give Bacillus tuberculosis as the example.

2. Coccus

Cocci are oval or spherical in shape and are described in the notes as among the smallest known bacteria.

Form	Arrangement	Example in Notes
Micrococcus	Each coccus remains free and individual	Micrococcus luteus
Diplococcus	Cocci occur in pairs	Diplococcus pneumoniae
Streptococcus	Cocci occur in chains	Streptococcus lactis
Staphylococcus	Cocci form irregular groups or grape-like bunches	Staphylococcus aureus

3. Spiral or Helical Bacteria

These bacteria are helical, corkscrew-shaped or coiled. The notes describe two forms:

Comma-shaped

They resemble a small curved rod or possess a single curve. Example: Vibrio cholerae.

Spiral

The body is twisted spirally. Example: Spirillum volutans.

Structure of Bacteria

The handwritten bacterial cell diagram shows a typical prokaryotic bacterial cell with a cell wall, plasma membrane, cytoplasm, nucleoid, ribosomes, storage granules, fimbriae and flagellum. :contentReference[oaicite:1]{index=1}

Simplified Structure of a Bacterial Cell

Components of a Bacterial Cell

1. Cell Wall

The cell wall is the outer protective covering of the bacterial cell.

According to the notes, it is composed of mucopeptide or peptidoglycan. It protects the internal contents of the cell.

2. Capsule or Slime Layer

The bacterial cell may secrete gelatinous substances around its cell wall forming a slime layer.

When this layer is compact and well organized, it is referred to as a capsule and the bacterium is called capsulated.

If it is loosely arranged, the notes describe the bacteria as non-capsulated. The layer is composed mainly of polysaccharides and proteins.

3. Cell Membrane

The cell membrane lies inside the cell wall and is made of lipids and proteins.

The source notes describe finger-like infoldings known as mesosomes. Respiratory enzymes are said to occur on them, and they are associated in the notes with respiration and DNA replication.

4. Cytoplasm

The cytoplasm lies inside the cell membrane. Membrane-bound cell organelles are absent.

70S ribosomes and reserve food materials occur in the cytoplasm.

5. Nucleoid

A well-organized nucleus is absent. The nuclear material is represented by a single circular DNA molecule forming the nucleoid.

The DNA is naked and lacks histone protein according to the notes.

6. Fimbriae or Pili

Fimbriae or pili are minute hair-like structures present on the surface of the bacterial cell wall.

They help bacterial cells attach to a host. The notes also associate pili with sexual reproduction during conjugation.

Flagella and Types of Flagellation

Flagella are hair-like locomotory structures found on bacterial cells. According to the notes, they are single-stranded structures.

Type	Arrangement
Atrichous	Bacteria without flagella
Monotrichous	Only one flagellum
Amphitrichous	One flagellum at each end
Cephalotrichous	A bunch of flagella at one end
Lophotrichous	Bunches of flagella at both ends
Peritrichous	Flagella distributed all over the body

Bacterial Life Style: Mode of Nutrition

On the basis of nutrition, bacteria are divided into:

Autotrophic bacteria
Heterotrophic bacteria

A. Autotrophic Bacteria

Bacteria capable of preparing their own food are called autotrophic bacteria.

1. Photoautotrophic Bacteria

Photoautotrophic bacteria synthesize organic food from inorganic raw materials using energy obtained from light.

They contain photosynthetic pigments such as bacteriochlorophyll.

The handwritten notes describe Chlorobium as an example. They use carbon dioxide in food synthesis but do not use water as the source of hydrogen.

Because oxygen is not evolved, this type is described in the source as anoxygenic photosynthesis.

Example: Chlorobium limicola.

2. Chemoautotrophic Bacteria

Bacteria that prepare their own food using energy obtained from chemical reactions are known as chemoautotrophic bacteria.

The synthesis of food using chemical energy is known as chemosynthesis.

B. Heterotrophic Bacteria

Bacteria that cannot prepare their own food and obtain their nutrition from other sources are called heterotrophic bacteria.

1. Saprophytic Bacteria

Saprophytic bacteria obtain food from dead and decaying organic matter.

They secrete enzymes which decompose complex organic compounds into simpler forms.

Example: Pseudomonas.

2. Symbiotic Bacteria

Some bacteria live in close association with another organism where both partners are mutually benefited.

Such bacteria are known as symbiotic bacteria.

Example: Rhizobium.

3. Parasitic Bacteria

Parasitic bacteria obtain their food from the living tissues of plants or animals on which they grow.

The organism on which they live is called the host, and the bacteria are called parasites.

Example: Salmonella typhi.

Economic Importance of Bacteria

A. Beneficial or Positive Importance

1. Role in Agriculture

Bacteria act on dead bodies and convert complex organic substances into simpler substances such as nitrates, sulphates and phosphates.

Some bacteria help fix atmospheric nitrogen in symbiotic association with the roots of legumes.

2. Role in Sanitation

Bacteria help check the accumulation of waste by feeding on decaying organic matter.

3. Role in Industries

The notes describe bacterial use in industries such as:

Dairy industries for ripening milk
Production of flavours in butter
Vinegar manufacture
Fermentation of sugary substances
Tanning of hides
Retting of plant fibres

4. Role in Medicine

Various bacteria are used in the production of medicines, antibiotics, antisera and vaccines.

5. Production of Enzymes

According to the notes, enzymes such as amylase and protease are manufactured from Bacillus subtilis.

6. Production of Vitamins

The source mentions Clostridium butylicum in connection with the synthesis of riboflavin.

B. Harmful Importance

1. Diseases

Bacteria may cause serious diseases in humans, animals and plants.

Examples listed in the notes include pneumonia, Asiatic cholera, diphtheria, tuberculosis and anthrax.

2. Food Spoilage

Some saprophytic bacteria spoil food by causing decay.

Example: Clostridium.

3. Cotton Deterioration

The handwritten notes mention Spirochaeta cytophaga as an organism that destroys cotton and materials made from it.

Cyanobacteria

Cyanobacteria are commonly known as blue-green algae.

Characteristics of Cyanobacteria

They are prokaryotic organisms.
They are mainly unicellular, although colonial and filamentous forms also occur.
They are mostly aquatic. Some occur in freshwater and some are marine.
A true nucleus and membrane-bound cell organelles are absent.
Photosynthetic pigments include C-phycocyanin, C-phycoerythrin and chlorophyll-a.
Reserve food is stored in the form of cyanophycean starch.
Sexual reproduction is absent.
They reproduce by vegetative and asexual methods.
Examples mentioned in the notes include Nostoc, Anabaena and Oscillatoria.

Nostoc

Occurrence

Nostoc is described in the notes as a filamentous blue-green alga occurring in colonies.

It is found in aquatic habitats such as ponds, lakes and ditches, as well as in agricultural fields.

Structure

Nostoc consists of simple, unbranched filamentous structures called trichomes.

Each trichome consists of rounded or oval cells. A trichome along with its individual hyaline sheath is referred to as a filament.

Many filaments are interwoven to form a colony. The colony appears as a bluish-green or yellowish mass of jelly.

Simplified Structure of Nostoc

Reproduction in Nostoc

The handwritten notes describe the following methods:

1. Fragmentation

A Nostoc colony breaks into several smaller filaments due to mechanical, physiological or other factors.

Each fragment can develop further.

2. Hormogones

Hormogones are smaller fragments of filaments formed within the colony.

They escape from the colony, develop into new filaments and later form new colonies.

3. Akinetes

During unfavourable conditions, vegetative cells accumulate food material and develop thick walls around themselves.

These spore-like resting structures are called akinetes.

When favourable conditions return, they germinate and develop into new filaments.

4. Heterocysts

Heterocysts are larger cells occurring in the filament between vegetative cells.

According to the handwritten notes, heterocysts can give rise to new filaments and subsequently new colonies.

Economic Importance of Cyanobacteria

Large colonies of Nostoc are edible and are described as rich in nitrogenous substances.
Cyanobacteria may occur in association with lichens, Anthoceros, roots of cycads and other plants.
Such associations may benefit plants through fixation of atmospheric nitrogen.
Cyanobacteria increase the nitrogen content of soil.
Some cyanobacteria such as Lyngbya are mentioned as being used as antibiotics.
They may serve as food for several aquatic animals.
Species of Anabaena are mentioned in the notes in relation to controlling mosquito larvae.
Some cyanobacteria grow on walls and roofs during rainy seasons, where they may cause discoloration, corrosion and leakage.

Quick Revision

Monerans are prokaryotic organisms.
A true nucleus and membrane-bound organelles are absent.
Their nuclear material consists of naked circular DNA.
Kingdom Monera includes Eubacteria and Archaebacteria in the classification shown in the notes.
Eubacteria includes bacteria and cyanobacteria.
Bacteria are unicellular and possess 70S ribosomes.
Binary fission is the common mode of bacterial reproduction.
Major bacterial shapes include bacillus, coccus and spiral forms.
The bacterial cell includes a cell wall, cell membrane, cytoplasm, nucleoid, ribosomes, pili and sometimes flagella.
Flagellar arrangements include atrichous, monotrichous, amphitrichous, cephalotrichous, lophotrichous and peritrichous.
Bacteria may be autotrophic or heterotrophic.
Autotrophic bacteria may be photoautotrophic or chemoautotrophic.
Heterotrophic bacteria may be saprophytic, symbiotic or parasitic.
Bacteria have both beneficial and harmful economic effects.
Cyanobacteria are commonly called blue-green algae.
Cyanobacteria contain chlorophyll-a and phycobilin pigments.
Sexual reproduction is absent in cyanobacteria.
Nostoc forms filamentous colonies.
Reproduction in Nostoc occurs by fragmentation, hormogones, akinetes and heterocysts according to the notes.
Many cyanobacteria help increase soil nitrogen.

Important Questions

Write the general characteristics of Kingdom Monera.
Classify Kingdom Monera.
What are Eubacteria and Archaebacteria?
Define bacteria and bacteriology.
Write the general characteristics of bacteria.
Classify bacteria on the basis of shape.
Differentiate between bacilli, cocci and spiral bacteria.
Write the different arrangements of cocci with examples.
Describe the structure of a bacterial cell.
Write the functions of the bacterial cell wall.
What is a capsule or slime layer?
What is a nucleoid?
What are fimbriae or pili?
Describe the types of bacterial flagellation.
Classify bacteria on the basis of mode of nutrition.
What are photoautotrophic bacteria?
What are chemoautotrophic bacteria?
Differentiate between saprophytic, symbiotic and parasitic bacteria.
Write the beneficial economic importance of bacteria.
Write the harmful effects of bacteria.
What are cyanobacteria?
Write the characteristics of cyanobacteria.
Describe the occurrence and structure of Nostoc.
Explain reproduction in Nostoc.
What are hormogones?
What are akinetes?
What are heterocysts?
Write the economic importance of cyanobacteria.