Cyanophage and its Details

Cyanophage and its Details Cyanobacteria ž Cyanobacteria are microscopic, photosynthetic, aquatic bacteria. ž It is generally found in fresh water, Lake, Ocean, Streams, Moist soil and rock. ž Cyanobacteria is also called as blue-green algae and also called as cyanophyte. ž They are aquatic, photosynthetic, prokaryotic bacteria so its name was renamed as Cyanobacteria. ž … Read more

Growth of a Bacterial Cell

The growth of a Bacterial Cell It can be defined as an orderly increase in the quantity of all cell components of a cell.The cell increases in its size, shape and weight and further undergoes cell division.The bacterial cell undergoes different growth phases.This growth phases of the bacterial cell can be studied by plotting a … Read more

Nomenclature of Bacterial Cell

Nomenclature of Bacterial Cell

In this world, there are millions of microorganisms.These microorganism are present everywhere and each organism has its unique and special features.There is a huge diversity in morphological, physical, and chemical characters of these organism.So due to such a huge diversity it is very important to name and classify these organism.Nomenclature and classification of these micro-organism can avoid confusion and misunderstanding .Due to huge diversity of these organism they are named into different names which leads to confusion.So naming these organism in a systematic and logical way is very important.

These organism are named in two ways.

  1. Common Name
  2. Scientific Name

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Cell Wall of Gram Negative Bacteria

Cell wall of Gram negative bacteria

Cell wall of Gram negative bacteria is more rigid and thick then Gram postive bacteria.

It is made up of two layers

1. Peptidoglycan

2. Outer cell wall layer

Component of cell wall of Gram negative cell wall
Component of peptidoglycan of Gram negative cell wall

1. Peptidoglycan

  • It is present in between outer wall layer and cell membrane.
  • The structure is similar as gram positive cell wall.
  • There are some minor differences in the Gram positive and Gram negative peptidoglycan structure.
  • The differences are as follows:-
  1. The third amino acid of tetrapeptide side chainin Gram positive cell wall is L-lysin which is replaced by Mesodiaminopimilic acid in Gram negative cell wall.
  2. All N-acetymuramic acid molecules are not linked to tetrapeptide side chain.
  3. Cross bridges are not made up of glycin molecule they are made up of peptide bond.

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Microbiology – Cell Wall of Gram Positive Bacteria.


  • A bacterial cell shows various parts and these parts have specific structure and functions.
  • These parts are separated by a rigid cell wall some parts are on the internal side of the cell wall and some parts are on the external side of the cell wall.
  • The parts present on the internal side of the cell wall are cell membrane, cytoplasm, nuclear region, reserve food material etc.
  • The cellular parts present on external to the cell wall are flagella, capsule and pilia.

Structure and function of Cell wall

  • The cell wall is the outer covering of bacterial cell in absence of capsule.
  • This cell wall is rigid in nature which imparts a proper shape to bacteria.
  • Cell wall encloses all internal parts of the cell.
  • On the basis of typical structure, composition and Gram staining they are classified

A)   Gram-positive bacteria.

B)   Gram-negative bacteria. Types of bacterial cell

Types of bacterial cell

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Microbiology – Morphology of Bacterial cell

Morphology means systematic study of external characters of bacteria.

Morphology of bacterial cell deals with study of

  1. Size of bacteria.
  2. Shape of bacteria.
  3. Arrangement of bacteria.

1. Size of bacteria.

  • Size of bacterial cell is less than 3 micrometer.
  • The bacteria are microscopic in nature and are visible only under compound microscope.
  • These bacteria may be spherical,cylindrical or spiral in shape.
  • Size of a spherical shape bacteria can be measures in diameter.
  • Size of a cylindrical bacteria is measured by its length and width.
  • In spiral shape bacteria length is measured but due to spiral form it is not exact.
  • As we know all bacteria are microscopic in nature so their size is also measured under microscope.
  • Size of bacteria is measured  by using calibrated slide and calibrated  occular compound microscope is used.
  • The above method of measuring size is called as micrometry.
  • The size of bacteria can also be measured by electron microscopic micrometry.
  • Units of measurement used in bacteriology are
  1. Micron or micrometer.
  2. Nanometer (nm) or Millimicron.
  3. Angstrom (A°)
  • The conversion are as follows
  • 1 μm = 10-3 mm = 10-4cm = 10-6 meter1 nm = 10-3 μm = 10-6 mm1 A0 = 10-1 nm = 10-4 m =10-7 mm
  • Size of spherical bacteria or cocci ranges from 0.5 to 3.0 μm.
  • Size of cylindrical or rod shape bacteria ranges from 0.15 μm to 2.0 μm in width and 0.5 μ to 20 μ in lenght.
  • The small size of bacteria have large surface area for entry of nutrients, water and exit of waste.

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