Bacteria Culture, isolation and purification

Separation of a single bacteria species from a multi species colony is known as isolation of bacteria. In nature a single type of bacteria species is usually occurs as only one component of a large and complex population containing many other organisms.

To study the characteristics of one species, that species must be isolated in pure culture. It is often helpful to use a selective method first; such a method can increase the relative proportion of the desired species in the population so that it can be more easily isolated.

A variety of techniques have been developed in isolation of bacterial colony. Some of these techniques are

  • The streak-plate technique
  • Roll tube technique
  • The pour-plate and spread-plate technique
  • Micro-manipulator technique.

We have followed the streak plate technique because it is easy and widely acceptable one.

The streak-plate technique:

The following materials and method had been used to isolate bacterial colony in streak-plate technique.


  • Nicrom ware
  • Nutrient agar plate
  • Sprit lamp
  • A plate with bacterial colony
  • Transfer loop

Method of Culture, isolation and purification of Bacteria:

By means of transfer loop a portion of the mixed culture is placed on the surface of an agar media and streaked across the surface. This manipulation thin out the bacterial on the agar surface so that some individual bacteria are separated from each other.

Before streaking a nicrom ware has heated until it become radish.After heated we weight some moment to cool it. We cool it in normal temperature. Than the loop was used to transfer a portion of culture from the culture Petri dish and was placed on a nutrient agar plate and streaked parallel from left to right repeatedly.

In this way we streaked all the side of the plate and lastly we streaked a line in the middle of the plate. Then we placed the Petri dish in incubator for 24 hours. We observed on the next day.

Result and observation of Bacteria Culture, isolation and purification:

In the next day we observed the Petri dish. We found that some colony are formed that we separate the colony visually with the shape and size of the colony.

Finally: We just isolated the bacteria and identify the species of bacteria. Do you like this post! Please share it with your friends.

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