It also used to avoid having to pipette very small volumes (1-10 µl) to make a dilution of a solution. The main purpose of serial dilution technique is to find out the concentration or the cell counts of an anonymous sample by counting the number of colonies that are cultured from the serial dilutions of the sample. This cannot be done with a fluid solution because 1) the purity of the specimen cannot be determined and 2) there is no means to count the cells in a liquid. Due to the microbes’ even dispersion across the agar plate, it is possible to count them with precision. The following process generates a series of pour plates from multiple dilutions, however spread plates (sample distributed on top of solidified agar) can also be utilised. Colonies develop within the agar, as well as on its surface and beneath it (between the agar and the lower dish). The agar solidifies, trapping the bacterial cells within its matrix. The standard plate count is a reliable method for determining the number of bacteria and fungus.Ī series of serial dilutions are created, and a sample of each is added to a liquefied agar medium before the medium is poured into a petri dish. In 1883, he published the article Detection Methods for Microorganisms in Water. Robert Koch is credited with discovering a method for enumerating microorganisms, which was initially used to the research of water quality. Additionally, it can be used to obtain a precise measurement of bacterial or other microorganism populations in a sample, and to isolate pure cultures of microorganisms from mixed populations. This technique is used in many laboratory procedures, including microbiology and biochemistry experiments, to accurately measure the concentration of a sample and to prepare solutions with a known concentration. The main objective of serial dilution is to reduce the concentration of a substance, typically a chemical or biological sample, in a series of steps. Serial dilution only reduces the number of bacteria/viable cells but doesn’t separate them like in other techniques like Flow Cytometry. This makes it easier to calculate the cell numbers in the primary solution by calculating the total dilution over the whole series. In serial dilution, the cell count or density gradually decreases as the serial number increases in each step. In the laboratory, this method is used to decrease the counts of viable cells within a culture to simplify the operation. In a single and very simple word, Serial dilution is a laboratory technique, in which a stepwise dilution process is performed on a solution with an associated dilution factor. Serial dilution involves performing a series of sequential dilution steps to convert a dense solution to a more usable concentration. Hey there, you might be thinking, what is serial dilution?Īs the term indicates, it is a series of succeeding dilutions that performed to create a less dense or less concentrated solution from a high dense or concentrated solution. This methodology is particular for bacterial counts (CFUs), but can be adapted for fungus (CFUs) and viruses (plaque-forming units, PFUs for viral counts).Īlso Read: MCQ on Serial Dilution What is a serial dilution? – serial dilution definition The objective may be to determine bacterial, fungal, or viral numbers. Following is a step-by-step process for solving dilution problems, followed by some practise problems. Most samples include an excessive number of microorganisms, necessitating successive dilution for accurate quantification. coli suspensions in nutritional broth, soil samples, and hamburger. It is routine practise to quantify microbial counts for both liquid and solid specimens, including E.
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