Question

Why do we need to dilute a bacterial culture to determine its OCD using the plate count method?

a. To enhance bacterial growth
b. To reduce contamination
c. To facilitate microscopic analysis
d. To expedite the culturing process

Answer 1

Bacterial cultures need to be diluted prior to determining their OCD using the plate count method to achieve countable colonies, reduce contamination, and ensure accurate measurement.

Step-by-step explanation:

In order to determine the OCD (original cell density) of a bacterial culture using the plate count method, it is necessary to dilute the culture. This is done to achieve a countable number of bacterial colonies on the agar plate for accurate measurement. Dilution helps in reducing overcrowding of colonies, making it easier to count and estimate the number of viable bacterial cells present in the original culture.

With a high concentration of bacteria, colonies may overlap, making it difficult to count each individual colony. Additionally, overcrowding can suppress the growth of some bacteria, leading to an underestimation of the true OCD. Dilution counters these issues by creating a spread of colonies that can be easily distinguished and counted.

Diluting the bacterial culture also helps to reduce contamination. By diluting the sample, any contaminants that may have been present in the original culture are also diluted, making it easier to identify and isolate the desired bacteria.