Give an account on agar bacteria separation?

Answer Posted / jyotsna

Nutrient agar is used throughout the world to provide a
solid surface containing medium for the growth of bacteria
and fungi.
There are different methods for the isolation of bacteria
by using agar plates.
Streak plate method:
A small amount of sample is transferred onto the surface of
a suitable, solid agar medium either by loop or transfer
needle. This is then streaked in such a Way as to provide
successive dilutions and ultimately to have well isolated
colonies. Streaking may be done in any of the ways. In each
case the sample becomes progressively diluted and at the
end of streak one would expect the well isolated colonies.

Spread plate method:
An aliquot of the diluted sample is placed onto the agar
surface and is spread uniformly with a sterile, bent glass
rod. Both streaking and spreading methods are useful
particularly in separating aggregates of cells in the
sample.
Pour plate method:
The sample should be diluted successively with sterile
water. The agar medium is maintained in molten state at 45°
C. One ml of each dilution is added to each sterile Petri
dish to which is then poured 9ml of sterile, cool agar
medium. The contents are thoroughly mixed, and allowed to
solidify. The dishes are incubated at suitable temperature.
After few days, different kinds of microbe: grow as
separate colonies. Cells from individual colony may be
picked up for a subculture.

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