Streak plate method

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Streak plate method :-

This method of isolation was developed in the lab of Robert Koch. In this method by means of a transfer loop a portion of bacterial speciman is placed on the surface of agar medium and the speciman is streaked over the surface in the petridish with a platinum wire loop. The successive streaking thins out the culture sufficiently. When streaking is perfactly performed, the bacterial cells will be far apart in some areas of plate to ensure that colony developing from one cell is not merged with that growing from another. The plate is incubated at proper temperature over night so that the cells can grow and multiply to give isolated colonies. Next day the isolated colonies can be observed in the N. agar plate. Each isolated colony is the progeny of the single cell and hence a pure culture is obtained. One can easily pick up the colony by means of transfer loop and then make them suspended in S/D/W phials to get pure culture suspension.

Isolation of bacteria

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Isolation of bacteria

Defination :-

The separation of one kind of bacteria fron the mixture of many different kinds is called isolation.


Introduction :

A pure culture consists of a population of only one kind of species of microorganisms, all derived from a single parent microorganism on the solid media. Thus the culture prepared from an isolated colony is termed as a pure culture. Robert Koch the germen physician introduced some pure culture techniques. When the organisms are growing with the other species their characteristics may be altered/influensed by the effect of other species. So to various characteristics accurately they should be studied separately. And for that isolation should be carried out.


Various techniques are available with the help of which different microbial species can be isolated & grown as pure culture. These methods are as follows....

Cocci Bacteria

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