Explain Spread Plate Method - Pure Culture Techniques?

In this method, diluted microbial suspension containing about 30 to 300 colonies is spread uniformly on the agar surface with a sterile bent rod (spreader). Look at the Figure, which graphically illustrates the spread plate method. By repeated picking and restreaking of a well-isolated colony, a pure culture can be obtained.

The dispersed cells develop into isolated colonies. The method can also be used for quantitation of microbial number in the sample, as you will learn in the next practical.Briefly, in spread plate method, a small volume of the diluted sample (about 0.1 ml) is transferred to the centre of a pre-poured solidified agar plate and then spread uniformly over the surface of the medium with a sterile L-shaped glass rod or spreader. After incubation, the dispensed cells form isolated colonies on agar surface, the number of which is used to calculate the amount of microbes in a given sample. It is important that the surface of the plate be dry so that the culture that is spread soaks in.