Question

What is the main advantage and disadvantage a pour plate has over a spread plate in counting bacteria?

Answer 1

Solution: These are the two micorbiology techniques used mainly for isolating pure colonies. These techniques have also been used for studying antimicrobial activities of drugs. In the spread plate technique a small volume of dilute microbial mixture with approximately30 to 300 cells are plated on to the agar surface. Each viable cells grow into a complete separate colony. The isolation of colonies is easier in spread plate because all colonies appear on the surface of the agar plates.

Along with spread plate, another technique pour platr also can yield isolated colonies . Here the original sample will be reduced several times to obtain separate colonies when plated. In this technique we normally add agar with a temperature around 45 degree celsius. The pour plate technique can detect at lower concentrations than spread platr method because of the larger volume of the sample. Another advantage is that it doesnot require pre-drying of surface. One of the highlighted disadvantage with pou plate method is that during this technique hot agar is used. The hot agar nay injure or kill sensitive bacterial/fungal cells. Due to this reason the spread plate technique sometimes get higher counts than pour plate. Appearance of sub-surface colonies sometimes make difficulty for isolation in pour plate technique.