Question

how would loop dilution, spread plate, and streak plate isolation techniques be affective by the use of selective medium

Answer 1

Answer:

Loop dilution, spread plate, and streak plate isolation technique are effective by using the selective medium. In loop dilution, there is the plating of diluted samples mixed with melted agar medium in successive tubes. This is used for the distribution of bacterial cells in the medium.

In the spread plate technique, the mixed culture of microorganisms is diluted in a series of tubes containing sterile physiological saline. A drop of the diluted liquid from each tube is spread evenly over the solid medium for inoculation. When the colonies develop, some plates have well-isolated colonies.

The streak plate method is used to isolate the pure cultures of bacteria. During this streaking, a dilution gradient is established in the medium. Due to this dilution gradient, the growth is not mixed. Each colony represent a pure culture.

All these three techniques have slightly mixed colonies sometimes. This is because these techniques involve manual procedure. The manual procedure for isolation has an error.

Selective medium is used to suppress the growth of some microbes while allowing the growth of desired microbes. The selective medium is an agar-based solid medium in which individual colonies can be isolated. Different chemicals are used in specific combinations to isolate the desired microorganisms. Selective medium helps in separating the bacteria with chemical selection. Therefore, the use of a selective medium at the near-final stage of all three techniques can provide more pure and isolated samples of bacterial species.