Last updated on June 11th, 2021Pour plate method is commonly the method of choice for counting the variety of colony-forming bacteria existing in a liquid specimen. Since the sample is combined with the molten agar medium, a larger volume deserve to be supplied than v the spread plate. In this method, a addressed amount the inoculum (generally 1 ml) indigenous a broth/sample is placed in the center of a sterile Petri dish utilizing a sterile pipette. Molten cooled agar (approx. 15mL) is then poured right into the Petri food containing the inoculum and mixed well. After the solidification of the agar, the bowl is inverted and also incubated in ~ 37°C because that 24-48 hours.Microorganisms will thrive both ~ above the surface and also within the medium. Nests that flourish within the medium typically are tiny in size and also maybe confluent; the couple of that grow on the agar surface room of the exact same size and also appear favor those on a streak plate. Every (both large and small) colony is very closely counted (using magnifying swarm counter if needed). Each swarm represents a “colony-forming unit” (CFU).The number of microorganisms existing in the particular test sample is determined using the formula:CFU/mL= CFU * dilution element * 1/aliquot

Pouring the molten agar medium

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Collect one party of sterile molten agar (containing 15 mL of melted Plate count Agar or any kind of other standard society media) from the water bath (45°C).Hold the party in the appropriate hand; remove the cap with the little finger that the left hand.Flame the neck of the bottle.Lift the lid the the Petri food slightly through the left hand and pour the sterile molten agar into the Petri dish and replace the lid.Flame the neck that the bottle and also replace the cap.Gently swirl the bowl on the benchtop to mix the society and the medium thoroughly. Ensure the the tool covers the plate evenly and also do not slip the agar over the sheet of the Petri dish.Allow the agar to fully gel there is no disturbing it, it will take about 10 minutes.Seal and incubate the key in an inverted position at 37°C for 24-48 hours.
Overview of to water plate method and spread out plate method

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After 24-48 hours, counting all the nests (again: note that the embedded swarms will be much smaller than those which occur to kind on the surface). A magnifying colony counter can help in counting tiny embedded colonies.Calculate CFU/mL utilizing the formula: CFU/mL= CFU * dilution aspect * 1/aliquot(the volume the diluted specimen (aliquot) is one of two people 0.1 or 1.0 mL)

Disadvantages of pour plate method

Preparation because that the pour plate method is time-consuming compared with the streak plate/and or spread plate technique.Loss the viability of heat-sensitive organisms coming into contact with warm agar.Embedded swarms are lot smaller than those which take place to be on the surface. Thus, one have to be mindful to count these so the none room overlooked.Reduced growth rate that obligate aerobes in the depth of the agar.References and further readingsBasic useful Microbiology A hand-operated by culture for basic Microbiology (SGM)