Principle Microbiology

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.