Serial dilution is a technique used to reduce the concentration of a substance in a sample. It is commonly used in microbiology to determine the number of bacteria in a given sample, as well as to isolate and identify bacterial strains.
The process of serial dilution involves mixing a known volume of a sample with a known volume of a diluent, such as water or saline. This mixture is then transferred to a new container and mixed with an equal volume of diluent. This process is repeated multiple times, resulting in a series of progressively more dilute samples.
For example, if a sample contains 100 bacteria and is mixed with 10 ml of diluent, the resulting mixture will have a concentration of 10 bacteria per ml. If this mixture is then mixed with 10 ml of diluent, the resulting mixture will have a concentration of 1 bacteria per ml. This process can be repeated multiple times to create a series of progressively more dilute samples.
The number of bacteria in each dilution can be determined by plating a known volume of the dilution onto a Petri dish containing agar, a solid growth medium. The agar is incubated at a suitable temperature and conditions for the bacteria to grow and form colonies. The number of colonies that form on the agar can then be counted and used to calculate the number of bacteria in the original sample.
Serial dilution is a valuable tool in microbiology because it allows researchers to determine the concentration of bacteria in a sample, even if the sample contains a large number of bacteria. It is also useful for isolating and identifying bacterial strains, as different bacterial strains will form distinct colonies on the agar.
Additionally, serial dilution is used in the laboratory to determine the minimum inhibitory concentration (MIC) of an antimicrobial agent. The MIC is the lowest concentration of the agent that is able to inhibit the growth of bacteria. By performing a series of serial dilutions with the antimicrobial agent, researchers can determine the MIC and evaluate the effectiveness of the agent against different bacterial strains.