Bacteria, Morphology and structure of bacteria with Diagram In detail


Bacteria is a smallest living organism having a cellular structure in nature Bacteria is a smallest living organism having a cellular structure in nature . They are classified as microorganism due to unicellular prokaryotic. The study of Bacteria is called bacteriology.

  1. Bacteria found everywhere in environment, such as water, soil, air, dust partial, plants and in animals.
  2. They also present in hot water at 70 C or higher temperature.
  3. They found in large quantity, e.g. one gram of fertile soil contains more than hundred million and in fresh milk more than 3000 million bacteria found.

Morphology of Bacteria:

Morphology included size, shape, structure and arrangement of organism.

Size of bacteria:

Bacteria are very small and unicellular. It size is 0.5-1 um in diameter and 0.1-10 um in length.

Shape of Bacteria:

Bacteria have constant shape. They cover with a rigid cell wall. it,s present in varieties of shape due to this they are classified on the basic of according to shape.

  1. Cocci
  2. Bacilli
  3. Spirilla
  4. Spirochetes


Sphere in shape e.g. streptococcus pneumonia cause pneumonia.


Rod shape bacteria e.g. Lactobacillus present in milk.


There shape is curve with a twist or turn in shape. If curve in not complete so its called viriloid and more completed curve in called helical.


They can control their flexible shape and twist. These bacteria a ridge in nature.

Structure of Bacteria Call:

Bacteria contain many vital components. Some are outer component and some insider component of cell wall.

External component:

  • Flagella
  • Fimbriae or pili

These are vital component which are present in all types of bacteria, but some bacteria consist of some special component that only present in certain species.

Special component:

  1. Cell wall
  2. Cytoplasmic membrane
  3. Specialized membrane
  4. The Cytoplasm
  5. Plasmids
  6. Spores and Cysts
  7. Gas Vacuole
Structure of Bacteria

Capsule & slim layer:

Many bacteria secrete a stick fluid like substance that make a protective layer around the cell wall is called Capsule. Some time this layer diffuses then it’s called slim layers.

  1. Bacteria capsules are composing with polysaccharide material, but some bacteria capsule made up with polypeptide.
  2. Main function of capsule they help the bacteria to attach to substance and make colony.  Its also act as an antibiotic in bacteria to resist the diseases.


Bacteria move from one place to other with the help of locomotion organ is called flagella.

  1. Flagella consist of hair like and helical cytoplasmic appendages structure.
  2. It may be present in both side or one side of the bacteria.

Fimbriae or pili:

  1. Pilli are rod like structure that composed of Pillin Protein.
  2. They help to cell to cell attachment.
  3. Basically, they act as sex organ in bacteria.
  4. it helps in mating of bacteria to generating new generation.

Cell wall:

  1. Cell wall present b/w the cytoplasmic membrane and capsule.
  2. It is rigid in nature and provide the shape to bacteria.
  3. Cell wall is compulsory component for bacterial growth.
  4. Those bacterial missing cell wall not complete their growth very well or stop.

On the basic of cell wall bacteria are divide into type.

  1. Gram Positive
  2. Gram Negative

Cytoplasmic membrane:

  1. It is present under the cell wall and cover the living matter of cell.
  2. Semi- permeable in nature.
  3. It composes of 60-70 % protein and 20-30% phospholipid.
  4. Protein are embedded between Bilayer of phospholipid.
  5. It is ATP producing site and attach with the DNA of bacteria.

Specialized membrane:

Infoldings are present in cytoplasmic membrane that make complex structure and increase surface area.

There are two types of Specialized membrane.

  1. Mesosomes membrane
  2. Photosynthetic membrane

Mesosomes membrane:

  1. They are infoldings in structure of cell membrane.
  2. They appear in cell division and attach with DNA.
  3. They help to separate the daughter cell after replication.
  4. They add the cross-wall b/w the bacterial daughter cell.

Photosynthetic membrane:

  1. Tubular like infoldings are produce by cytoplasmic membrane this is called Photosynthetic membrane.
  2. It is founded on photosynthetic bacteria only.
  3. They contain pigment and resemble in Blue green algae.


  1. The bacterial cell cover by a layer is called cytoplasmic membrane in cytoplasm.
  2. They differentiated into liquid part that called cytosol.
  3. This part is rich with ribosome and concentrated due to nuclear material.

Composition of Cytosol:

Cytosol is concentrated, complex solution of amino acid, inorganic acid, peptide, protein, nitrogenous bases, enzyme, vitamin, coenzyme that provide environment for metabolic process or activity.


  1. Ribosome is protein synthesis body that present in cytoplasm freely.
  2. They are dense in nature.
  3. Every ribosome consists of two subunits.
  4. One is 50S and second in 30S with equal amount of Protein and RNA.
  5. They are smaller than eukaryotic ribosome.


  1. Bacterial chromosome consists of 5*106 DNA molecule base pair and 1mm in length.
  2. Small part of protein is also present in it.
  3. DNA is primitive in nature.
  4. Most of bacteria have concentrated DNA and cytoplasmic region protect the DNA, that region is called nuclear body or nuclear region.
  5. Some bacteria have single stranded DNA, and some have double stranded DNA.


  1. Bacteria have smaller ring of DNA is called plasmid.
  2. Every plasmid has ability to self-replication due to presence own Gene.
  3. Some plasmid has ability to resist against the antibodies.
  4. They could produce enzyme that fight against the infection causing agent.
  5. Some plasmid integrating the bacterial DNA Chromosome.


  1. Bacteria produce endospore that act like a resistance bodies against the heat, desiccation and help to overcome the unfavorable growth situation.
  2. At favorable condition the spores germinate to make a new cell.


  1. In few bacteria complete cell developed into a thick walled that called cysts.
  2. Cysts also known as resistance body.
  3. They become new individual when condition is favorable.

Gas Vacuole:

  1. Gas vacuole provide buoyancy in some bacteria aquatic species.
  2. They are rigid, cylindrical and impermeable to water.
  3. They are protein in nature.
  4. Gas pass this membrane.

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