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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